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			<title>Rhetoric and Propaganda</title>
			<link>http://72.14.177.54/logic/Rhetoric_and_Propaganda</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* Emotional words */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;=Sophistry and the fine art of rhetoric emotionalism? - bah!=&lt;br /&gt;
&lt;br /&gt;
I usually leave such nonsense to this robotic roustabout Ever since I began the logic  page, I have naturally considered sources that only deal with the subject of logic. Recently, I have decided this was a mistake.&lt;br /&gt;
&lt;br /&gt;
My feeling now is that in order to really delineate logic from other modes of persuasion, I would need to specifically point out the other methods. This has led to my addition of a Sophistry section - on the art of rhetoric.&lt;br /&gt;
&lt;br /&gt;
==A little history on the Sophists - the first advocates of rhetoric==&lt;br /&gt;
&lt;br /&gt;
The ancient Greek Sophists were the first organized group of philosophers to point out the fallacy of naive empiricism - the natural assumption that what we take in with our senses represents the totality of reality, without error. The Sophists argued that in a rapidly changing and evolving world, no one could get a true reading on reality. As Heraclitus said: How can we know anything in a world that never is, but instead is always becoming something else? While many Sophists, such as Gorgias took this to the extreme of nihilism, denying that anyone could ever know anything (so, how did he know that?), all sophists agreed that our view of reality was at best subjective, prone to error, and not capable of creating certain premises for logical arguments. Today we tend to agree with the Sophists on this point.&lt;br /&gt;
&lt;br /&gt;
Since empirical evidence was flawed at its root, the Sophists claimed that the only valid means of persuasion was rhetoric - an appeal to our emotions. Rhetorical appeals clearly had benifits over empiricism - we could be more certain of our own emotions, and they could be counted on to motivate us to action.&lt;br /&gt;
&lt;br /&gt;
The Sophists took this view to &amp;quot;heart' and became experts in the use of rhetoric, to the point that it irritated their enemies - who then became desparate to find something that could be certain - i.e.: clear, unchanging and perfect, that would be suitable for a premise.&lt;br /&gt;
&lt;br /&gt;
Soon, Socrates would come up with the idea of reals, a mental construct of reality, that suited this need. Eventually, the concept of reals would be used in Aristotles art of logic. Since the school of the rationalists and the empiricists won out over the Sophists, and, as history is written by the victors, the Sophists would come to be seen in disparaging terms, to the point that the words sophistry and rhetoric now have negative connotations, even amongst the common man.&lt;br /&gt;
&lt;br /&gt;
However, to be fair, it should be stated that rhetoric does have a value - and in fact, this is recognized by its still popular use today - mostly in the hands of (not, surprisingly) lawyers and politicians. While the extreme skepticism of the sophists is in disfavor, (Betrand Russell makes the point that I inferred above, that extreme skepticism is merely a dogmatic belief system, and as such prone to error itself) it would do us good to know the methods of the sophists today.&lt;br /&gt;
&lt;br /&gt;
So, in order to better explain the value of logic, and to explain how politicians work, I have listed the basics of what I consider to be the inferior tool of rhetoric here:&lt;br /&gt;
&lt;br /&gt;
==Rhetoric - The use of persuasive words to win an argument==&lt;br /&gt;
&lt;br /&gt;
There are two general ways to argue, although both forms are not necessarily mutually exclusive. The first is through logical argument, the second, through rhetorical persuasuion. In logic, we attempt to convince through logical necessity - if one accepts our premises, they must accept our conclusions. While emotions of course play a part, they are not directly appealed to. When one attempts to persuade as opposed to convince, they rely more on emotion than on logic.&lt;br /&gt;
&lt;br /&gt;
Therefore, in rhetoric, we refers to &amp;quot;premises&amp;quot; as appeals. When one wants to appeal to another's emotions, they call upon different strategies - they attempt to personalize the argument, appeal to our own vanities. Here are some of the most common methods:&lt;br /&gt;
&lt;br /&gt;
===Anecdotes, Stories, Metaphors===&lt;br /&gt;
&lt;br /&gt;
These cast an issue in a favorable or unfavorable light, or can highlight or suppress certain aspects. They work by suggesting a likeness between a character and the listener, or a situation and the listener's. In logic we see that this appeal often commits the logical errors of the small sample bias, weak comparison, and excluded middle.&lt;br /&gt;
&lt;br /&gt;
===Double-bind===&lt;br /&gt;
&lt;br /&gt;
One way of getting a child to eat her vegetables is to offer a &amp;quot;choice&amp;quot; &amp;quot;Would you like peas or spinach?&amp;quot; Regardless of the alternative chosen, your desired objective is met. &amp;quot;Which kind of environmental bureaucracy do you want -- one that stifles business and innovation, or one that burdens American industry with impossible extra costs?&amp;quot; In logic we see that this appeal often commits the false dichotomy error.&lt;br /&gt;
&lt;br /&gt;
===Contingency===&lt;br /&gt;
 &lt;br /&gt;
This works by getting you to accept both parts of a statement because of how they are linked; one part might be reasonable enough by itself, but. . .&lt;br /&gt;
&lt;br /&gt;
&amp;quot;Unless you want the earth to turn to a barren crust, you must oppose corporate capitalist pigs, tooth and nail.&amp;quot; In logic we see that this appeal often commits the logical error of false dichotomy or hasty generalization.&lt;br /&gt;
&lt;br /&gt;
===Rapport===&lt;br /&gt;
&lt;br /&gt;
How does the author go about building a sense of friendliness and receptivity on the part of the audience? Some methods are friendly introductions (&amp;quot;my friends&amp;quot;), complimenting, showing respect, speaking the speakers 'language,' and conveying optimism. These are important communicative techniques! Rapport is important. We just have to be aware of its use in persuasive contexts. Used car salesmen use rapport. In logic we see that this appeal often commits the Red Herring Fallacy.&lt;br /&gt;
&lt;br /&gt;
===Authority===&lt;br /&gt;
&lt;br /&gt;
A speaker may claim in many ways to be an authority; sometimes external checking of this is called for. Sometimes the &amp;quot;authority&amp;quot; is specious, or openly fallicious. In logic we refer to phoney cases of authority as an &amp;quot;appeal to authority&amp;quot;, A perfect example would be &amp;quot;Dr. Laura&amp;quot; who, in fact, does not have a doctorate in psychology, but physiology. (If she attempted to do this in professional practice, she would be sanctioned by the APA)&lt;br /&gt;
&lt;br /&gt;
===Humor===&lt;br /&gt;
&lt;br /&gt;
Humor has a great way of defusing our critical faculties. Whenever Ronald Reagen couldn't deal with facts, he'd make a joke. The most famous case was his uttering &amp;quot;There you go again!&amp;quot; to Walter Mondale during a debate. The fact that Reagen was saying this because Mondale nailed him on a fact he couldn't escape from, was lost to the audience. They prefered the humor of Reagen to the reality of Mondale. In logic we refer to Reagen's use of humor as &amp;quot;missing the point&amp;quot;&lt;br /&gt;
&lt;br /&gt;
===Emotional words===&lt;br /&gt;
&lt;br /&gt;
Advertisers are especially keen about the emotional qualities of certain words, and the sway they can give a speaker, just by their associations. Consider the possible power of: winner, loser, infantile, powerful, lovely, courage, freedom, radical. How are these kinds of words employed to generate a certain response in the listener? What purposes are served? A fine example would be Newt Gingrich's &amp;quot;GOPAC&amp;quot; an organization that existed to postively define conservative values and negatively define liberal values. One should ask: If conservative values are clearly superior to liberal values, why would a conservative need to create an organization that purposely tried to redfine liberal values with negative words? Is this not a implicit admission from conservatives that both liberal and conservative values are in many way, on an equal par, and that that one must purposely attempt to create a distinction in order to devalue one of them? In logic we see that this appeal often commits the false &amp;quot;emotional reasoning&amp;quot;.&lt;br /&gt;
&lt;br /&gt;
===Pacing===&lt;br /&gt;
&lt;br /&gt;
How do you move a listener along to your conclusion? Certain phrases help a speaker move us from one idea to another, regardless of whether strong connection or evidence has been established. Don't let phrases like these lull your assessment of the argument: &amp;quot;Naturally...&amp;quot;; &amp;quot;Certainly then...&amp;quot;; &amp;quot;Surely...&amp;quot;; &amp;quot;Without question...&amp;quot; But we must question any of these terms, particularly when we have no proof of the validity of their appeals. In logic we see that this appeal often commits various fallacies of presumption, as well as circular logic and begging the question.&lt;br /&gt;
&lt;br /&gt;
===Questions===&lt;br /&gt;
&lt;br /&gt;
Jacobs points out 3 ways posing questions helps a persuader do her work.&lt;br /&gt;
1. A question can substitute for a request (recall the peas and spinach).&lt;br /&gt;
2. While a listener is searching for an answer, the speaker can give his own answer to the question. The listener is more likely to accept it than if it were given as an assertion.&lt;br /&gt;
3. A question can have a suggestion embedded in it. Sales people skillfully use questions to lead the listener and control the discussion. In logic we recognize that true questions are not logical arguments at all - making them the perfect tool for a rhetorician.&lt;br /&gt;
&lt;br /&gt;
===Absolutes===&lt;br /&gt;
&lt;br /&gt;
We've all heard &amp;quot;never say never&amp;quot;; any totalizing statement is likely to result in a fallacy. But words like &amp;quot;don't&amp;quot; and &amp;quot;must&amp;quot; creep in and can give a writer's statements and indisputable air. In logic we see that this appeal often commits the false dichotomy error or fallacies of presumption.&lt;br /&gt;
&lt;br /&gt;
==An overview of the technical aspects of Rhetoric - Grounds, Warrants and Conclusions==&lt;br /&gt;
&lt;br /&gt;
Much of this work is culled from Enviromental Sociology - by J. A. Hannigan&lt;br /&gt;
&lt;br /&gt;
Rhetoric, according to Hannigan, involves the deliberate use of language in order to persuade, without providing logical proofs.&lt;br /&gt;
&lt;br /&gt;
Rhetoric can be said to be based on two methods: One of Emotionalism, or appealing to strong subjective emotional states (during which people usualy don't make the best decisions, wouldn't you agree?) and the second on Aesthetics, or the concept that whatever best appeals to you is what is true. A fine proponent of this is any politician, who usually makes the claim that whatever you yourself desire is what is best for the country. Sounds ridiculous? Well, why do Republicans claim that Tax cuts are the solution to every problem while liberals believe a losening of restrictions is always what is needed? Because they are playing to the aesthetic desires of their constituents! (For more, see philos, dictionary section.)&lt;br /&gt;
&lt;br /&gt;
Now, these emotional and aethetic rhetorical statements contain 3 principal components: grounds, warrants and conclusions. Let's go over them.&lt;br /&gt;
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===Grounds===&lt;br /&gt;
&lt;br /&gt;
Grounds are the data furnished by the speaker to support his cause. This includes:&lt;br /&gt;
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Persuasive definitions: (Slanted definitions i.e. a person against abortion can be called either a &amp;quot;pro lifer&amp;quot; OR &amp;quot;anti choice&amp;quot; depending upon which side is referring to him or her.)&lt;br /&gt;
&lt;br /&gt;
Unscientific statistics, (often biased, if not wholesale falsified - i.e. Ronald Reagan's use of statistics), and/or&lt;br /&gt;
&lt;br /&gt;
Case study examples - Easily identifiable victims, usually of a rare and extreme nature - i.e. Rodney King beating by L.A. police is held to be indicative of normal police/black populace interaction, or , on the other side, Ronald Reagan's use of a fictitious welfare queen (a complete lie) is held to be proof of the misuse of welfare.&lt;br /&gt;
&lt;br /&gt;
Again, case study examples are shown by psychological study to be extremely convincing, since one personal example bears more weight than a bookload of negating statistics. For proof, try telling a person afraid of air travel that jets are safer than cars. (Also, see my Social Psychology page for more...)&lt;br /&gt;
&lt;br /&gt;
One should note from this open definition, that it is entirely possible for rhetoric to include valid, logical data. Usually, however, even when this is the case, it is often used in emotional or unscientific ways, or along with a conclusion that goes much further than the valid evidence supports.&lt;br /&gt;
&lt;br /&gt;
===Warrants===&lt;br /&gt;
&lt;br /&gt;
Warrants are justifications for the speaker to demand action.&lt;br /&gt;
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Usually, a claim that basic rights have been violated or impinged upon. Two main modes are used:&lt;br /&gt;
&lt;br /&gt;
====Rhetoric of rationality====&lt;br /&gt;
&lt;br /&gt;
Our sense of logic must compel us to agree. It makes sense for others to agree with the speaker, since they will benefit by agreeing. This is the most valid of rhetoric, because, again, it comes closest to apeing the art of logic. However, while appearing like logic, often rhetoric is tinged with emotionalism, slanted views or unobjective judgements.&lt;br /&gt;
&lt;br /&gt;
====Rhetoric of Rectitude====&lt;br /&gt;
&lt;br /&gt;
Our values or morality should drive us to agree. No pretense of logic is made - instead, other, more important drives should motivate us, that go beyond logic. Hmmmm...&lt;br /&gt;
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Within these two basic modes, stereotypes are called upon, called rhetorical idioms:&lt;br /&gt;
&lt;br /&gt;
====Rhetorical Idioms====&lt;br /&gt;
&lt;br /&gt;
These are schemas or groups of cognitions that one stereotypically has about certain areas of moral significance:&lt;br /&gt;
&lt;br /&gt;
Rhetoric of loss: We are losing our innocence, our ability to enjoy nature&lt;br /&gt;
Rhetoric of unreason: we are being manipulated by a conspiracy - that somehow avoids are detection - but this is just further proof of its insidiousness! (Hey, if we could detect it, then it wouldn't be a conspiracy, right?)&lt;br /&gt;
Rhetoric of calamity: Favorite of religion - Deteriorism - the world is falling to pieces and judgement is at hand, therefore, we should change this (but, if it is preordained, can you change it? Or, even, should you??)&lt;br /&gt;
Rhetoric of entitlement: We have the RIGHT to kick the foreigners out of our country, etc. I haven't made a nazi reference in a few paragraphs, so I will note that our favorite Fuhrer, Adolf Hitler, used this technique, to justify his actions towards the Jews.&lt;br /&gt;
Rhetoric of endangerment: We must build 50,000 nuclear bombs, or the soviets will be feeding us borsch by June. And borsch sucks!&lt;br /&gt;
&lt;br /&gt;
====Rhetorical motifs====&lt;br /&gt;
&lt;br /&gt;
These methods all use recurrent metaphors - with an unbelievable persuasive power to change others minds, regardless of the reality of the situation. Examples include the claim that aids is a plague, or that the hole in the ozone is a ticking time bomb, or that we are suffering under a worldwide population explosion. They appeal to all facets of rhetoric, from emotional appeal, to moral to logic. The sad truth is that all of us have swallowed more than a few of them whole, without any critical examination!&lt;br /&gt;
&lt;br /&gt;
(Example: - There is no ozone hole - a recolored infrared reading of ozone leaves the THINNING LAYER of ozone clear, making it look to non professionals that no ozone exists over the arctic circle. Aids is not a plague, its a sexually transmitted disease (also, through blood transfusions) and it has hardly killed off 1/2 of the worlds population like the true plagues did, and lastly, the population in Europe is decreasing, and leveling off in America - its only in 3rd world nations where the growth is still quite high (and even there, the population increase comes from longer longevity, not increasing birthrate.) None of this is intended to say these are not problems, its only intended to show that rhetoric causes overstated misperceptions in the cause of rectifying what the speakers honestly feel are horrible problems.&lt;br /&gt;
&lt;br /&gt;
===Conclusions=== &lt;br /&gt;
&lt;br /&gt;
What action is needed to solve this problem. Usually this is simply stated as just agree/vote with/for us, and we will do the job...&lt;br /&gt;
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==How to further delineate Rhetoric from logic - look for &amp;quot;Intent signals&amp;quot;==&lt;br /&gt;
&lt;br /&gt;
I've certainly provided you with much already that stresses the differences between logic and rhetoric, but there is yet another indicator. There are things to look for in persuasive language that reveal putative self-serving motivations. Self-interest is fine, but too much of it, especially in the apparent pursuit of helping others, should cause us to question the integrity of the speaker. We call statements that reveal an abundance of self interest &amp;quot;intent signals&amp;quot; - i.e. what someone's real intent may be. Whether the presence of any of these in writing is cause for rejection requires analysis; their presence should call up further examination.&lt;br /&gt;
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Look for the following themes...&lt;br /&gt;
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===Us vs. Them===&lt;br /&gt;
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Does the speaker see two &amp;quot;sides,&amp;quot; with the other side being in some way inferior or denigrated? This happens all the time in environmental discourse, and often tends to cloud the real issues, and impede useful analysis. Many techniques of propaganda employ this technique: name calling, touting how great it is to &amp;quot;belong,&amp;quot; using one-sided testimonials of famous people, simplifying issues for slogans, emphasizing being on the right side of the competition.&lt;br /&gt;
&lt;br /&gt;
===Supremacy===&lt;br /&gt;
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Although there is nothing wrong with asserting superiority, it can suggest a need that is stronger than the desire to give a sound argument.&lt;br /&gt;
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===Absolute Certainty===&lt;br /&gt;
&lt;br /&gt;
Science doesn't provide it; scholarly research doesn't. Mathematics has it, but only within its self-defined deductive systems. When someone asserts they know something with absolute certainty, it can really only be based on self-evidence, faith, or mythology.&lt;br /&gt;
&lt;br /&gt;
===Righteous indignation===&lt;br /&gt;
&lt;br /&gt;
To quote Jacobs from his text On Rhetoric (1994, p. 74):&lt;br /&gt;
&lt;br /&gt;
When someone is so full of guiltless virtue and vengeance because of &amp;quot;unjust treatment,&amp;quot; his information is likely to be biased and inaccurate. Ultimately, this could hurt a worthy cause. Admittedly, what is truth and what is worthy are difficult things to know. But if this is not appreciated by a persuader, it could indicate he has taken an easy path to his position. It shows he may not have carefully analyzed his assertions. It is not likely he has open-mindedly compared his ideas to other viewpoints. The listener should thus question his information. &lt;br /&gt;
 &lt;br /&gt;
==Propaganda==&lt;br /&gt;
&lt;br /&gt;
There are numerous rhetorical devices used in propaganda. Here are the most commonly employed propaganda tools used by Bill O'Reilly:&lt;br /&gt;
&lt;br /&gt;
===The seven propaganda devices include:===&lt;br /&gt;
&lt;br /&gt;
* Name calling -- giving something a bad label to make the audience reject it without examining the evidence;&lt;br /&gt;
* Glittering generalities -- the opposite of name calling;&lt;br /&gt;
* Card stacking -- the selective use of facts and half-truths;&lt;br /&gt;
* Bandwagon -- appeals to the desire, common to most of us, to follow the crowd;&lt;br /&gt;
* Plain folks -- an attempt to convince an audience that they, and their ideas, are &amp;quot;of the people&amp;quot;;&lt;br /&gt;
* Transfer -- carries over the authority, sanction and prestige of something we respect or dispute to something the speaker would want us to accept; and&lt;br /&gt;
* Testimonials -- involving a respected (or disrespected) person endorsing or rejecting an idea or person.&lt;/div&gt;</description>
			<pubDate>Sun, 11 Mar 2012 07:27:25 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Rhetoric_and_Propaganda</comments>		</item>
		<item>
			<title>How Does A Materialist Account for Logic?</title>
			<link>http://72.14.177.54/logic/How_Does_A_Materialist_Account_for_Logic%3F</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* Common Responses */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;You probably already know how this complaint goes:&lt;br /&gt;
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&amp;quot;How can you account for axioms in a materialistic universe? What part of your brain are axioms located in? Can you actually point to some neurons and say 'these are what the axioms really are'? Also, since the axioms of math are carried around in people's heads, are there really millions of little axioms of math running around? Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...&amp;quot; &lt;br /&gt;
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Let's take this apart, piece by piece:&lt;br /&gt;
&lt;br /&gt;
==How do you account for the 'laws of logic' in a materialistic universe?==&lt;br /&gt;
&lt;br /&gt;
This question contains a false presumption. And to reveal it, I ask the following: 'The' laws of logic? Which set of laws? For which logic? First-order logic, first-order predicate logic, second-order predicate logic, modal logic, fuzzy logic? Which one? Logic is not a monolithic entity, and there is no one set of 'laws' for all of logic. Some logical systems do not require axioms at all. The set of axioms for the sentential, or propositional, logic is {} - the empty set.&lt;br /&gt;
&lt;br /&gt;
&amp;quot;The point is that there can be no axioms in propositional logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything in predicate logic is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&amp;quot;- Gregory Lopez.&lt;br /&gt;
&lt;br /&gt;
==The Basic Metaphysical Requirements for any Logical System==&lt;br /&gt;
&lt;br /&gt;
Now that we have done away with the blunders attached to that misunderstanding, let's explain the basic metaphysics required for the creation of an a priori system - the existence of sentient brains. The basic axioms of existence, identity and consciousness - the so called laws of reason (which are prior to any logical system '''and''' NOT part of logic itself), are necessary elements of reason; to reason one must first exist, and exist as something. These axioms are therefore implicitly inescapable - an explicit awareness of these axioms is another matter. &lt;br /&gt;
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We can express this truth thusly: &lt;br /&gt;
&lt;br /&gt;
To exist is to exist as something. And to be aware of this, is to be conscious. To update Descartes, we might say:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;I exist, therefore I think&amp;quot;&lt;br /&gt;
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These axioms of reason are necessary truths, given the existence of consciousness. They are defended through retortion. But they are '''not''' a part of logic, they exist prior to the formation (or learning) of any set of logical rules. Other rules, such as the other laws of classical logic, can also be gleaned a priori, all of them flow from the axiom of identity (i.e. classical logic, a system of tautologies, can be traced back to the axiom of identity). The specifics of which rules we create do not matter here; what matters is as long as we have sentient brains, we will have the basis for the creation of any a priori system.&lt;br /&gt;
&lt;br /&gt;
To 'explain' the human invention of logical systems as somehow the work of God is to explain precisely nothing at all.  No one who ever asserts this putative 'solution' ever defines this 'god' in a noncontradictory way, nor do they ever explain how this 'god' provides the foundation for logic. If they were to undertake an examination of their assertion they'd soon recognize that referencing the supernatural as foundation for a natural system leads to an infinitely greater problem than working out the metaphysics for logic, to whit: supernatural references are broken terms.  Invoking &amp;quot;god&amp;quot; to explain anything is the very abdication of reason and insight.&lt;br /&gt;
&lt;br /&gt;
== What part of your brain are axioms (or abstractions) located in?==&lt;br /&gt;
&lt;br /&gt;
The cerebral cortex, frontal lobes. http://www.waiting.com/brainanatomy.html#anchor2587568&lt;br /&gt;
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&amp;quot;Also, since the axioms of math are carried around in people's heads, are there really billions of little axioms of math running around?&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Billions of representations of the same axioms. Billions of sentient brains coming to the same, necessary, analytic, unavoidable, a priori conclusion, just as billions of different bits of falling matter all conform to the same phenomenon of nature that we can summarize in one law: the law of gravity. &lt;br /&gt;
&lt;br /&gt;
If you fail to find it puzzling how 'different pieces of matter' can all conform to the same law of gravity, then you ought to re-examine your supposed puzzlement over axioms. The process is similar. Billions of sentient brains encountering the same, singular reality - the unavoidable basic metaphysics of our universe. If you are looking for a missing 'constant' for the materialistic account, it is this: the universe. You've misplaced the universe. One universe with a basic set of unavoidable, inescapable metaphysics. One universe imprinting itself onto phylogenetically similar sentient beings, who are able to draw the same abstractions from the same stimuli, based on the same rules... &lt;br /&gt;
&lt;br /&gt;
Axioms, are abstractions that exist in a brain. The reason we see the 'same axiom' in different brains is because the same idea can be gleaned, analytically, a priori, by similar brains in the same exact universe. The same idea can be represented in multiple copies - the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses.&lt;br /&gt;
&lt;br /&gt;
==Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...==&lt;br /&gt;
&lt;br /&gt;
Ah, but you forget something else: Abstract entities written on a page have no meaning in and of themselves. They are interactive phenomena - a sentient brain is required to interpret them and provide them with 'meaning'. Thus, when we say that the number &amp;quot;eighteen&amp;quot; is written on a page, what materialists are really saying is that this sensory input'18' through some social convention (some rule), yields the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
A word written on a page and the same word spoken and traveling as a wave through the air are not 'the same matter'. However, when I read the word, and when I hear the word, my brain eventually interprets them the same way, producing similar electrochemical responses with enough fidelity that slightly different brains can reproduce the same abstraction, based on the same rules.&lt;br /&gt;
&lt;br /&gt;
Of course, the mapping itself is completely arbitrary. Our written alphabet needn't be what it is, and we could choose totally different symbols to represent the same thing as the spoken word.&lt;br /&gt;
&lt;br /&gt;
==Common Responses==&lt;br /&gt;
&lt;br /&gt;
The Identity of Indiscernibles is usually formulated as follows: if, for every property F, object x has F if and only if object y has F, then x is identical to y. Or in the notation of symbolic logic:&lt;br /&gt;
&lt;br /&gt;
∀F(Fx ↔ Fy) → x=y.&lt;br /&gt;
&lt;br /&gt;
This formula can be used to demonstrate that if x shares the same properties of y, then x and y are the same entity.&lt;br /&gt;
&lt;br /&gt;
The argument continues:&lt;br /&gt;
&lt;br /&gt;
A material entity cannot be in more than one spatio-temporal location at the same time.&lt;br /&gt;
&lt;br /&gt;
Response: This claim is built on intellectual dishonesty, for it  fails to consider that abstractions are tokens or representations - formed in neurons by the same set of rules. However, leaving this aside, the claim fails even if we accept this bit of dishonest, as quantum physics tells us that there is no contradiction in having the same material entity in more than one spatio-temporal location:&lt;br /&gt;
&lt;br /&gt;
http://www.fizyka.umk.pl/~jkob/physnews/node30.html &lt;br /&gt;
&lt;br /&gt;
For more in the principle of Identity of indiscernibles and Liebnitz' transposition of the principle, the law of Indiscernability of Identicals, see here:&lt;br /&gt;
&lt;br /&gt;
http://plato.stanford.edu/entries/identity-indiscernible/#Rec&lt;/div&gt;</description>
			<pubDate>Sun, 11 Mar 2012 07:20:29 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:How_Does_A_Materialist_Account_for_Logic%3F</comments>		</item>
		<item>
			<title>How Does A Materialist Account for Logic?</title>
			<link>http://72.14.177.54/logic/How_Does_A_Materialist_Account_for_Logic%3F</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* What part of your brain are axioms (or abstractions) located in? */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;You probably already know how this complaint goes:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;How can you account for axioms in a materialistic universe? What part of your brain are axioms located in? Can you actually point to some neurons and say 'these are what the axioms really are'? Also, since the axioms of math are carried around in people's heads, are there really millions of little axioms of math running around? Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...&amp;quot; &lt;br /&gt;
&lt;br /&gt;
Let's take this apart, piece by piece:&lt;br /&gt;
&lt;br /&gt;
==How do you account for the 'laws of logic' in a materialistic universe?==&lt;br /&gt;
&lt;br /&gt;
This question contains a false presumption. And to reveal it, I ask the following: 'The' laws of logic? Which set of laws? For which logic? First-order logic, first-order predicate logic, second-order predicate logic, modal logic, fuzzy logic? Which one? Logic is not a monolithic entity, and there is no one set of 'laws' for all of logic. Some logical systems do not require axioms at all. The set of axioms for the sentential, or propositional, logic is {} - the empty set.&lt;br /&gt;
&lt;br /&gt;
&amp;quot;The point is that there can be no axioms in propositional logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything in predicate logic is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&amp;quot;- Gregory Lopez.&lt;br /&gt;
&lt;br /&gt;
==The Basic Metaphysical Requirements for any Logical System==&lt;br /&gt;
&lt;br /&gt;
Now that we have done away with the blunders attached to that misunderstanding, let's explain the basic metaphysics required for the creation of an a priori system - the existence of sentient brains. The basic axioms of existence, identity and consciousness - the so called laws of reason (which are prior to any logical system '''and''' NOT part of logic itself), are necessary elements of reason; to reason one must first exist, and exist as something. These axioms are therefore implicitly inescapable - an explicit awareness of these axioms is another matter. &lt;br /&gt;
&lt;br /&gt;
We can express this truth thusly: &lt;br /&gt;
&lt;br /&gt;
To exist is to exist as something. And to be aware of this, is to be conscious. To update Descartes, we might say:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;I exist, therefore I think&amp;quot;&lt;br /&gt;
&lt;br /&gt;
These axioms of reason are necessary truths, given the existence of consciousness. They are defended through retortion. But they are '''not''' a part of logic, they exist prior to the formation (or learning) of any set of logical rules. Other rules, such as the other laws of classical logic, can also be gleaned a priori, all of them flow from the axiom of identity (i.e. classical logic, a system of tautologies, can be traced back to the axiom of identity). The specifics of which rules we create do not matter here; what matters is as long as we have sentient brains, we will have the basis for the creation of any a priori system.&lt;br /&gt;
&lt;br /&gt;
To 'explain' the human invention of logical systems as somehow the work of God is to explain precisely nothing at all.  No one who ever asserts this putative 'solution' ever defines this 'god' in a noncontradictory way, nor do they ever explain how this 'god' provides the foundation for logic. If they were to undertake an examination of their assertion they'd soon recognize that referencing the supernatural as foundation for a natural system leads to an infinitely greater problem than working out the metaphysics for logic, to whit: supernatural references are broken terms.  Invoking &amp;quot;god&amp;quot; to explain anything is the very abdication of reason and insight.&lt;br /&gt;
&lt;br /&gt;
== What part of your brain are axioms (or abstractions) located in?==&lt;br /&gt;
&lt;br /&gt;
The cerebral cortex, frontal lobes. http://www.waiting.com/brainanatomy.html#anchor2587568&lt;br /&gt;
&lt;br /&gt;
&amp;quot;Also, since the axioms of math are carried around in people's heads, are there really billions of little axioms of math running around?&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Billions of representations of the same axioms. Billions of sentient brains coming to the same, necessary, analytic, unavoidable, a priori conclusion, just as billions of different bits of falling matter all conform to the same phenomenon of nature that we can summarize in one law: the law of gravity. &lt;br /&gt;
&lt;br /&gt;
If you fail to find it puzzling how 'different pieces of matter' can all conform to the same law of gravity, then you ought to re-examine your supposed puzzlement over axioms. The process is similar. Billions of sentient brains encountering the same, singular reality - the unavoidable basic metaphysics of our universe. If you are looking for a missing 'constant' for the materialistic account, it is this: the universe. You've misplaced the universe. One universe with a basic set of unavoidable, inescapable metaphysics. One universe imprinting itself onto phylogenetically similar sentient beings, who are able to draw the same abstractions from the same stimuli, based on the same rules... &lt;br /&gt;
&lt;br /&gt;
Axioms, are abstractions that exist in a brain. The reason we see the 'same axiom' in different brains is because the same idea can be gleaned, analytically, a priori, by similar brains in the same exact universe. The same idea can be represented in multiple copies - the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses.&lt;br /&gt;
&lt;br /&gt;
==Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...==&lt;br /&gt;
&lt;br /&gt;
Ah, but you forget something else: Abstract entities written on a page have no meaning in and of themselves. They are interactive phenomena - a sentient brain is required to interpret them and provide them with 'meaning'. Thus, when we say that the number &amp;quot;eighteen&amp;quot; is written on a page, what materialists are really saying is that this sensory input'18' through some social convention (some rule), yields the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
A word written on a page and the same word spoken and traveling as a wave through the air are not 'the same matter'. However, when I read the word, and when I hear the word, my brain eventually interprets them the same way, producing similar electrochemical responses with enough fidelity that slightly different brains can reproduce the same abstraction, based on the same rules.&lt;br /&gt;
&lt;br /&gt;
Of course, the mapping itself is completely arbitrary. Our written alphabet needn't be what it is, and we could choose totally different symbols to represent the same thing as the spoken word.&lt;br /&gt;
&lt;br /&gt;
==Common Responses==&lt;br /&gt;
&lt;br /&gt;
The Identity of Indiscernibles is usually formulated as follows: if, for every property F, object x has F if and only if object y has F, then x is identical to y. Or in the notation of symbolic logic:&lt;br /&gt;
&lt;br /&gt;
∀F(Fx ↔ Fy) → x=y.&lt;br /&gt;
&lt;br /&gt;
This formula can be used to demonstrate that if x shares the same properties of y, then x and y are the same entity.&lt;br /&gt;
&lt;br /&gt;
The argument continues:&lt;br /&gt;
&lt;br /&gt;
A material entity cannot be in more than one spatio-temporal location at the same time.&lt;br /&gt;
&lt;br /&gt;
Response: This claim confuses fails to consider that abstractions are tokens or representations - formed in neurons by the same set of rules. However, the claim is doubly false, for even if we presume that abstractions are in fact the same identical entity, quantum physics tells us that there is no contradiction in having the same material entity in more than one spatio-temporal location:&lt;br /&gt;
&lt;br /&gt;
http://www.fizyka.umk.pl/~jkob/physnews/node30.html &lt;br /&gt;
&lt;br /&gt;
For more in the principle of Identity of indiscernibles and Liebnitz' transposition of the principle, the law of Indiscernability of Identicals, see here:&lt;br /&gt;
&lt;br /&gt;
http://plato.stanford.edu/entries/identity-indiscernible/#Rec&lt;/div&gt;</description>
			<pubDate>Sun, 11 Mar 2012 07:16:42 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:How_Does_A_Materialist_Account_for_Logic%3F</comments>		</item>
		<item>
			<title>How Does A Materialist Account for Logic?</title>
			<link>http://72.14.177.54/logic/How_Does_A_Materialist_Account_for_Logic%3F</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* The Basic Metaphysical Requirements for any Logical System */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;You probably already know how this complaint goes:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;How can you account for axioms in a materialistic universe? What part of your brain are axioms located in? Can you actually point to some neurons and say 'these are what the axioms really are'? Also, since the axioms of math are carried around in people's heads, are there really millions of little axioms of math running around? Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...&amp;quot; &lt;br /&gt;
&lt;br /&gt;
Let's take this apart, piece by piece:&lt;br /&gt;
&lt;br /&gt;
==How do you account for the 'laws of logic' in a materialistic universe?==&lt;br /&gt;
&lt;br /&gt;
This question contains a false presumption. And to reveal it, I ask the following: 'The' laws of logic? Which set of laws? For which logic? First-order logic, first-order predicate logic, second-order predicate logic, modal logic, fuzzy logic? Which one? Logic is not a monolithic entity, and there is no one set of 'laws' for all of logic. Some logical systems do not require axioms at all. The set of axioms for the sentential, or propositional, logic is {} - the empty set.&lt;br /&gt;
&lt;br /&gt;
&amp;quot;The point is that there can be no axioms in propositional logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything in predicate logic is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&amp;quot;- Gregory Lopez.&lt;br /&gt;
&lt;br /&gt;
==The Basic Metaphysical Requirements for any Logical System==&lt;br /&gt;
&lt;br /&gt;
Now that we have done away with the blunders attached to that misunderstanding, let's explain the basic metaphysics required for the creation of an a priori system - the existence of sentient brains. The basic axioms of existence, identity and consciousness - the so called laws of reason (which are prior to any logical system '''and''' NOT part of logic itself), are necessary elements of reason; to reason one must first exist, and exist as something. These axioms are therefore implicitly inescapable - an explicit awareness of these axioms is another matter. &lt;br /&gt;
&lt;br /&gt;
We can express this truth thusly: &lt;br /&gt;
&lt;br /&gt;
To exist is to exist as something. And to be aware of this, is to be conscious. To update Descartes, we might say:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;I exist, therefore I think&amp;quot;&lt;br /&gt;
&lt;br /&gt;
These axioms of reason are necessary truths, given the existence of consciousness. They are defended through retortion. But they are '''not''' a part of logic, they exist prior to the formation (or learning) of any set of logical rules. Other rules, such as the other laws of classical logic, can also be gleaned a priori, all of them flow from the axiom of identity (i.e. classical logic, a system of tautologies, can be traced back to the axiom of identity). The specifics of which rules we create do not matter here; what matters is as long as we have sentient brains, we will have the basis for the creation of any a priori system.&lt;br /&gt;
&lt;br /&gt;
To 'explain' the human invention of logical systems as somehow the work of God is to explain precisely nothing at all.  No one who ever asserts this putative 'solution' ever defines this 'god' in a noncontradictory way, nor do they ever explain how this 'god' provides the foundation for logic. If they were to undertake an examination of their assertion they'd soon recognize that referencing the supernatural as foundation for a natural system leads to an infinitely greater problem than working out the metaphysics for logic, to whit: supernatural references are broken terms.  Invoking &amp;quot;god&amp;quot; to explain anything is the very abdication of reason and insight.&lt;br /&gt;
&lt;br /&gt;
== What part of your brain are axioms (or abstractions) located in?==&lt;br /&gt;
&lt;br /&gt;
The cerebral cortex, frontal lobes. http://www.waiting.com/brainanatomy.html#anchor2587568&lt;br /&gt;
&lt;br /&gt;
&amp;quot;Also, since the axioms of math are carried around in people's heads, are there really billions of little axioms of math running around?&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Billions of representations of the same axioms. Billions of sentient brains coming to the same, necessary, analytic, unavoidable, a priori conclusion, just as billions of different bits of falling matter all conform to the same phenomenon of nature that we can summarize in one law: the law of gravity. &lt;br /&gt;
&lt;br /&gt;
If you fail to find it puzzling how 'different pieces of matter' can all conform to the same law of gravity, then you ought to re-examine your supposed puzzlement over axioms. The process is similar. Billions of sentient brains encountering the same, singular reality - the unavoidable basic metaphysics of our universe. If you are looking for a missing 'constant' for the materialistic account, it is this: the universe. You've misplaced the universe. One universe with a basic set of unavoidable, inescapable metaphysics. One universe imprinting itself onto phylogenetically similar sentient beings, who are able to draw the same abstractions from the same stimuli, based on the same rules... &lt;br /&gt;
&lt;br /&gt;
Axioms, are abstractions that exist in a brain. The reason we see the 'same axiom' in different brains is because the same idea can be gleaned, analytically, a priori, by similar brains in the same exact universe. The same idea can be represented in multiple copies - the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
==Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...==&lt;br /&gt;
&lt;br /&gt;
Ah, but you forget something else: Abstract entities written on a page have no meaning in and of themselves. They are interactive phenomena - a sentient brain is required to interpret them and provide them with 'meaning'. Thus, when we say that the number &amp;quot;eighteen&amp;quot; is written on a page, what materialists are really saying is that this sensory input'18' through some social convention (some rule), yields the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
A word written on a page and the same word spoken and traveling as a wave through the air are not 'the same matter'. However, when I read the word, and when I hear the word, my brain eventually interprets them the same way, producing similar electrochemical responses with enough fidelity that slightly different brains can reproduce the same abstraction, based on the same rules.&lt;br /&gt;
&lt;br /&gt;
Of course, the mapping itself is completely arbitrary. Our written alphabet needn't be what it is, and we could choose totally different symbols to represent the same thing as the spoken word.&lt;br /&gt;
&lt;br /&gt;
==Common Responses==&lt;br /&gt;
&lt;br /&gt;
The Identity of Indiscernibles is usually formulated as follows: if, for every property F, object x has F if and only if object y has F, then x is identical to y. Or in the notation of symbolic logic:&lt;br /&gt;
&lt;br /&gt;
∀F(Fx ↔ Fy) → x=y.&lt;br /&gt;
&lt;br /&gt;
This formula can be used to demonstrate that if x shares the same properties of y, then x and y are the same entity.&lt;br /&gt;
&lt;br /&gt;
The argument continues:&lt;br /&gt;
&lt;br /&gt;
A material entity cannot be in more than one spatio-temporal location at the same time.&lt;br /&gt;
&lt;br /&gt;
Response: This claim confuses fails to consider that abstractions are tokens or representations - formed in neurons by the same set of rules. However, the claim is doubly false, for even if we presume that abstractions are in fact the same identical entity, quantum physics tells us that there is no contradiction in having the same material entity in more than one spatio-temporal location:&lt;br /&gt;
&lt;br /&gt;
http://www.fizyka.umk.pl/~jkob/physnews/node30.html &lt;br /&gt;
&lt;br /&gt;
For more in the principle of Identity of indiscernibles and Liebnitz' transposition of the principle, the law of Indiscernability of Identicals, see here:&lt;br /&gt;
&lt;br /&gt;
http://plato.stanford.edu/entries/identity-indiscernible/#Rec&lt;/div&gt;</description>
			<pubDate>Sun, 11 Mar 2012 07:16:04 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:How_Does_A_Materialist_Account_for_Logic%3F</comments>		</item>
		<item>
			<title>How Does A Materialist Account for Logic?</title>
			<link>http://72.14.177.54/logic/How_Does_A_Materialist_Account_for_Logic%3F</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* How do you account for the 'laws of logic' in a materialistic universe? */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;You probably already know how this complaint goes:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;How can you account for axioms in a materialistic universe? What part of your brain are axioms located in? Can you actually point to some neurons and say 'these are what the axioms really are'? Also, since the axioms of math are carried around in people's heads, are there really millions of little axioms of math running around? Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...&amp;quot; &lt;br /&gt;
&lt;br /&gt;
Let's take this apart, piece by piece:&lt;br /&gt;
&lt;br /&gt;
==How do you account for the 'laws of logic' in a materialistic universe?==&lt;br /&gt;
&lt;br /&gt;
This question contains a false presumption. And to reveal it, I ask the following: 'The' laws of logic? Which set of laws? For which logic? First-order logic, first-order predicate logic, second-order predicate logic, modal logic, fuzzy logic? Which one? Logic is not a monolithic entity, and there is no one set of 'laws' for all of logic. Some logical systems do not require axioms at all. The set of axioms for the sentential, or propositional, logic is {} - the empty set.&lt;br /&gt;
&lt;br /&gt;
&amp;quot;The point is that there can be no axioms in propositional logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything in predicate logic is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&amp;quot;- Gregory Lopez.&lt;br /&gt;
&lt;br /&gt;
==The Basic Metaphysical Requirements for any Logical System==&lt;br /&gt;
&lt;br /&gt;
Now that we have done away with the blunders attached to that misunderstanding, let's explain the basic metaphysics requires for the creation of an a priori system. The only metaphysic required for the creation of an a priori system is the existence of sentient brains. The basic axioms of existence, identity and consciousness - the so called laws of reason (prior to any logical system and not part of logic itself), are necessary elements of reason; to reason one must first exist, and exist as something. These axioms are therefore implicitly inescapable - an explicit awareness of these axioms is another matter. &lt;br /&gt;
&lt;br /&gt;
We can express this truth thusly: &lt;br /&gt;
&lt;br /&gt;
To exist is to exist as something. And to be aware of this is to be conscious.&lt;br /&gt;
&lt;br /&gt;
The axioms are necessary truths, given the existence of consciousness. They are defended through retortion. But they are not a part of logic, per se. Other rules, such as the other laws of classical logic, can also be gleaned a priori, all of them flow from the axiom of identity (i.e. classical logic, a system of tautologies, can be traced back to the axiom of identity). The specifics of which rules we create do not matter here; what matters is as long as we have sentient brains, we will have the basis for the creation of any a priori system.&lt;br /&gt;
&lt;br /&gt;
To explain the human invention of logical systems as somehow the indirect work of God is to explain precisely nothing at all. It is as good of an explanation as saying &amp;quot;it just happened.&amp;quot; No one who ever asserts it ever defines this 'god' in a noncontradictory way, nor do they ever explain how this 'god' provides the foundation. Invoking God to explain anything is the very abdication of reason and insight. It is giving up the investigation and search for truth and filling it with some supernatural nonsense (literally). Instead, I think that people like Paul Feyerabend, Karl Popper, and Thomas Kuhn give us a good idea about how science and human knowledge progresses.&lt;br /&gt;
&lt;br /&gt;
== What part of your brain are axioms (or abstractions) located in?==&lt;br /&gt;
&lt;br /&gt;
The cerebral cortex, frontal lobes. http://www.waiting.com/brainanatomy.html#anchor2587568&lt;br /&gt;
&lt;br /&gt;
&amp;quot;Also, since the axioms of math are carried around in people's heads, are there really billions of little axioms of math running around?&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Billions of representations of the same axioms. Billions of sentient brains coming to the same, necessary, analytic, unavoidable, a priori conclusion, just as billions of different bits of falling matter all conform to the same phenomenon of nature that we can summarize in one law: the law of gravity. &lt;br /&gt;
&lt;br /&gt;
If you fail to find it puzzling how 'different pieces of matter' can all conform to the same law of gravity, then you ought to re-examine your supposed puzzlement over axioms. The process is similar. Billions of sentient brains encountering the same, singular reality - the unavoidable basic metaphysics of our universe. If you are looking for a missing 'constant' for the materialistic account, it is this: the universe. You've misplaced the universe. One universe with a basic set of unavoidable, inescapable metaphysics. One universe imprinting itself onto phylogenetically similar sentient beings, who are able to draw the same abstractions from the same stimuli, based on the same rules... &lt;br /&gt;
&lt;br /&gt;
Axioms, are abstractions that exist in a brain. The reason we see the 'same axiom' in different brains is because the same idea can be gleaned, analytically, a priori, by similar brains in the same exact universe. The same idea can be represented in multiple copies - the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
==Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...==&lt;br /&gt;
&lt;br /&gt;
Ah, but you forget something else: Abstract entities written on a page have no meaning in and of themselves. They are interactive phenomena - a sentient brain is required to interpret them and provide them with 'meaning'. Thus, when we say that the number &amp;quot;eighteen&amp;quot; is written on a page, what materialists are really saying is that this sensory input'18' through some social convention (some rule), yields the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
A word written on a page and the same word spoken and traveling as a wave through the air are not 'the same matter'. However, when I read the word, and when I hear the word, my brain eventually interprets them the same way, producing similar electrochemical responses with enough fidelity that slightly different brains can reproduce the same abstraction, based on the same rules.&lt;br /&gt;
&lt;br /&gt;
Of course, the mapping itself is completely arbitrary. Our written alphabet needn't be what it is, and we could choose totally different symbols to represent the same thing as the spoken word.&lt;br /&gt;
&lt;br /&gt;
==Common Responses==&lt;br /&gt;
&lt;br /&gt;
The Identity of Indiscernibles is usually formulated as follows: if, for every property F, object x has F if and only if object y has F, then x is identical to y. Or in the notation of symbolic logic:&lt;br /&gt;
&lt;br /&gt;
∀F(Fx ↔ Fy) → x=y.&lt;br /&gt;
&lt;br /&gt;
This formula can be used to demonstrate that if x shares the same properties of y, then x and y are the same entity.&lt;br /&gt;
&lt;br /&gt;
The argument continues:&lt;br /&gt;
&lt;br /&gt;
A material entity cannot be in more than one spatio-temporal location at the same time.&lt;br /&gt;
&lt;br /&gt;
Response: This claim confuses fails to consider that abstractions are tokens or representations - formed in neurons by the same set of rules. However, the claim is doubly false, for even if we presume that abstractions are in fact the same identical entity, quantum physics tells us that there is no contradiction in having the same material entity in more than one spatio-temporal location:&lt;br /&gt;
&lt;br /&gt;
http://www.fizyka.umk.pl/~jkob/physnews/node30.html &lt;br /&gt;
&lt;br /&gt;
For more in the principle of Identity of indiscernibles and Liebnitz' transposition of the principle, the law of Indiscernability of Identicals, see here:&lt;br /&gt;
&lt;br /&gt;
http://plato.stanford.edu/entries/identity-indiscernible/#Rec&lt;/div&gt;</description>
			<pubDate>Sun, 11 Mar 2012 07:00:36 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:How_Does_A_Materialist_Account_for_Logic%3F</comments>		</item>
		<item>
			<title>How Does A Materialist Account for Logic?</title>
			<link>http://72.14.177.54/logic/How_Does_A_Materialist_Account_for_Logic%3F</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* How do you account for the 'laws of logic' in a materialistic universe? */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;You probably already know how this complaint goes:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;How can you account for axioms in a materialistic universe? What part of your brain are axioms located in? Can you actually point to some neurons and say 'these are what the axioms really are'? Also, since the axioms of math are carried around in people's heads, are there really millions of little axioms of math running around? Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...&amp;quot; &lt;br /&gt;
&lt;br /&gt;
Let's take this apart, piece by piece:&lt;br /&gt;
&lt;br /&gt;
==How do you account for the 'laws of logic' in a materialistic universe?==&lt;br /&gt;
&lt;br /&gt;
This question contains a false presumption. And to reveal it, I ask the following: 'The' laws of logic? Which set of laws? For which logic? First-order logic, first-order predicate logic, second-order predicate logic, modal logic, fuzzy logic? Which one? Logic is not a monolithic entity, and there is no one set of 'laws' for all of logic. Some logical systems do not require axioms at all. The set of axioms for the sentential, or propositional, logic is {} - the empty set.&lt;br /&gt;
''&lt;br /&gt;
&amp;quot;The point is that there can be no axioms in propositional logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything in predicate logic is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&amp;quot;'' - Gregory Lopez.&lt;br /&gt;
&lt;br /&gt;
==The Basic Metaphysical Requirements for any Logical System==&lt;br /&gt;
&lt;br /&gt;
Now that we have done away with the blunders attached to that misunderstanding, let's explain the basic metaphysics requires for the creation of an a priori system. The only metaphysic required for the creation of an a priori system is the existence of sentient brains. The basic axioms of existence, identity and consciousness - the so called laws of reason (prior to any logical system and not part of logic itself), are necessary elements of reason; to reason one must first exist, and exist as something. These axioms are therefore implicitly inescapable - an explicit awareness of these axioms is another matter. &lt;br /&gt;
&lt;br /&gt;
We can express this truth thusly: &lt;br /&gt;
&lt;br /&gt;
To exist is to exist as something. And to be aware of this is to be conscious.&lt;br /&gt;
&lt;br /&gt;
The axioms are necessary truths, given the existence of consciousness. They are defended through retortion. But they are not a part of logic, per se. Other rules, such as the other laws of classical logic, can also be gleaned a priori, all of them flow from the axiom of identity (i.e. classical logic, a system of tautologies, can be traced back to the axiom of identity). The specifics of which rules we create do not matter here; what matters is as long as we have sentient brains, we will have the basis for the creation of any a priori system.&lt;br /&gt;
&lt;br /&gt;
To explain the human invention of logical systems as somehow the indirect work of God is to explain precisely nothing at all. It is as good of an explanation as saying &amp;quot;it just happened.&amp;quot; No one who ever asserts it ever defines this 'god' in a noncontradictory way, nor do they ever explain how this 'god' provides the foundation. Invoking God to explain anything is the very abdication of reason and insight. It is giving up the investigation and search for truth and filling it with some supernatural nonsense (literally). Instead, I think that people like Paul Feyerabend, Karl Popper, and Thomas Kuhn give us a good idea about how science and human knowledge progresses.&lt;br /&gt;
&lt;br /&gt;
== What part of your brain are axioms (or abstractions) located in?==&lt;br /&gt;
&lt;br /&gt;
The cerebral cortex, frontal lobes. http://www.waiting.com/brainanatomy.html#anchor2587568&lt;br /&gt;
&lt;br /&gt;
&amp;quot;Also, since the axioms of math are carried around in people's heads, are there really billions of little axioms of math running around?&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Billions of representations of the same axioms. Billions of sentient brains coming to the same, necessary, analytic, unavoidable, a priori conclusion, just as billions of different bits of falling matter all conform to the same phenomenon of nature that we can summarize in one law: the law of gravity. &lt;br /&gt;
&lt;br /&gt;
If you fail to find it puzzling how 'different pieces of matter' can all conform to the same law of gravity, then you ought to re-examine your supposed puzzlement over axioms. The process is similar. Billions of sentient brains encountering the same, singular reality - the unavoidable basic metaphysics of our universe. If you are looking for a missing 'constant' for the materialistic account, it is this: the universe. You've misplaced the universe. One universe with a basic set of unavoidable, inescapable metaphysics. One universe imprinting itself onto phylogenetically similar sentient beings, who are able to draw the same abstractions from the same stimuli, based on the same rules... &lt;br /&gt;
&lt;br /&gt;
Axioms, are abstractions that exist in a brain. The reason we see the 'same axiom' in different brains is because the same idea can be gleaned, analytically, a priori, by similar brains in the same exact universe. The same idea can be represented in multiple copies - the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
==Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...==&lt;br /&gt;
&lt;br /&gt;
Ah, but you forget something else: Abstract entities written on a page have no meaning in and of themselves. They are interactive phenomena - a sentient brain is required to interpret them and provide them with 'meaning'. Thus, when we say that the number &amp;quot;eighteen&amp;quot; is written on a page, what materialists are really saying is that this sensory input'18' through some social convention (some rule), yields the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
A word written on a page and the same word spoken and traveling as a wave through the air are not 'the same matter'. However, when I read the word, and when I hear the word, my brain eventually interprets them the same way, producing similar electrochemical responses with enough fidelity that slightly different brains can reproduce the same abstraction, based on the same rules.&lt;br /&gt;
&lt;br /&gt;
Of course, the mapping itself is completely arbitrary. Our written alphabet needn't be what it is, and we could choose totally different symbols to represent the same thing as the spoken word.&lt;br /&gt;
&lt;br /&gt;
==Common Responses==&lt;br /&gt;
&lt;br /&gt;
The Identity of Indiscernibles is usually formulated as follows: if, for every property F, object x has F if and only if object y has F, then x is identical to y. Or in the notation of symbolic logic:&lt;br /&gt;
&lt;br /&gt;
∀F(Fx ↔ Fy) → x=y.&lt;br /&gt;
&lt;br /&gt;
This formula can be used to demonstrate that if x shares the same properties of y, then x and y are the same entity.&lt;br /&gt;
&lt;br /&gt;
The argument continues:&lt;br /&gt;
&lt;br /&gt;
A material entity cannot be in more than one spatio-temporal location at the same time.&lt;br /&gt;
&lt;br /&gt;
Response: This claim confuses fails to consider that abstractions are tokens or representations - formed in neurons by the same set of rules. However, the claim is doubly false, for even if we presume that abstractions are in fact the same identical entity, quantum physics tells us that there is no contradiction in having the same material entity in more than one spatio-temporal location:&lt;br /&gt;
&lt;br /&gt;
http://www.fizyka.umk.pl/~jkob/physnews/node30.html &lt;br /&gt;
&lt;br /&gt;
For more in the principle of Identity of indiscernibles and Liebnitz' transposition of the principle, the law of Indiscernability of Identicals, see here:&lt;br /&gt;
&lt;br /&gt;
http://plato.stanford.edu/entries/identity-indiscernible/#Rec&lt;/div&gt;</description>
			<pubDate>Sun, 11 Mar 2012 07:00:09 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:How_Does_A_Materialist_Account_for_Logic%3F</comments>		</item>
		<item>
			<title>How Does A Materialist Account for Logic?</title>
			<link>http://72.14.177.54/logic/How_Does_A_Materialist_Account_for_Logic%3F</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;You probably already know how this complaint goes:&lt;br /&gt;
&lt;br /&gt;
&amp;quot;How can you account for axioms in a materialistic universe? What part of your brain are axioms located in? Can you actually point to some neurons and say 'these are what the axioms really are'? Also, since the axioms of math are carried around in people's heads, are there really millions of little axioms of math running around? Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...&amp;quot; &lt;br /&gt;
&lt;br /&gt;
Let's take this apart, piece by piece:&lt;br /&gt;
&lt;br /&gt;
==How do you account for the 'laws of logic' in a materialistic universe?==&lt;br /&gt;
&lt;br /&gt;
This question contains a false presumption. And to reveal it, I ask the following: 'The' laws of logic? Which set of laws? For which logic? First-order logic, first-order predicate logic, second-order predicate logic, modal logic, fuzzy logic? Which one? Logic is not a monolithic entity, and there is no one set of 'laws' for all of logic. Some logical systems do not require axioms at all. The set of axioms for the sentential, or propositional, logic is {} - the empty set.&lt;br /&gt;
&lt;br /&gt;
[quote]&amp;quot;The point is that there can be no axioms in propositional logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything in predicate logic is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&amp;quot; - Gregory Lopez.[/quote]&lt;br /&gt;
&lt;br /&gt;
==The Basic Metaphysical Requirements for any Logical System==&lt;br /&gt;
&lt;br /&gt;
Now that we have done away with the blunders attached to that misunderstanding, let's explain the basic metaphysics requires for the creation of an a priori system. The only metaphysic required for the creation of an a priori system is the existence of sentient brains. The basic axioms of existence, identity and consciousness - the so called laws of reason (prior to any logical system and not part of logic itself), are necessary elements of reason; to reason one must first exist, and exist as something. These axioms are therefore implicitly inescapable - an explicit awareness of these axioms is another matter. &lt;br /&gt;
&lt;br /&gt;
We can express this truth thusly: &lt;br /&gt;
&lt;br /&gt;
To exist is to exist as something. And to be aware of this is to be conscious.&lt;br /&gt;
&lt;br /&gt;
The axioms are necessary truths, given the existence of consciousness. They are defended through retortion. But they are not a part of logic, per se. Other rules, such as the other laws of classical logic, can also be gleaned a priori, all of them flow from the axiom of identity (i.e. classical logic, a system of tautologies, can be traced back to the axiom of identity). The specifics of which rules we create do not matter here; what matters is as long as we have sentient brains, we will have the basis for the creation of any a priori system.&lt;br /&gt;
&lt;br /&gt;
To explain the human invention of logical systems as somehow the indirect work of God is to explain precisely nothing at all. It is as good of an explanation as saying &amp;quot;it just happened.&amp;quot; No one who ever asserts it ever defines this 'god' in a noncontradictory way, nor do they ever explain how this 'god' provides the foundation. Invoking God to explain anything is the very abdication of reason and insight. It is giving up the investigation and search for truth and filling it with some supernatural nonsense (literally). Instead, I think that people like Paul Feyerabend, Karl Popper, and Thomas Kuhn give us a good idea about how science and human knowledge progresses.&lt;br /&gt;
&lt;br /&gt;
== What part of your brain are axioms (or abstractions) located in?==&lt;br /&gt;
&lt;br /&gt;
The cerebral cortex, frontal lobes. http://www.waiting.com/brainanatomy.html#anchor2587568&lt;br /&gt;
&lt;br /&gt;
&amp;quot;Also, since the axioms of math are carried around in people's heads, are there really billions of little axioms of math running around?&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Billions of representations of the same axioms. Billions of sentient brains coming to the same, necessary, analytic, unavoidable, a priori conclusion, just as billions of different bits of falling matter all conform to the same phenomenon of nature that we can summarize in one law: the law of gravity. &lt;br /&gt;
&lt;br /&gt;
If you fail to find it puzzling how 'different pieces of matter' can all conform to the same law of gravity, then you ought to re-examine your supposed puzzlement over axioms. The process is similar. Billions of sentient brains encountering the same, singular reality - the unavoidable basic metaphysics of our universe. If you are looking for a missing 'constant' for the materialistic account, it is this: the universe. You've misplaced the universe. One universe with a basic set of unavoidable, inescapable metaphysics. One universe imprinting itself onto phylogenetically similar sentient beings, who are able to draw the same abstractions from the same stimuli, based on the same rules... &lt;br /&gt;
&lt;br /&gt;
Axioms, are abstractions that exist in a brain. The reason we see the 'same axiom' in different brains is because the same idea can be gleaned, analytically, a priori, by similar brains in the same exact universe. The same idea can be represented in multiple copies - the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
==Finally, how come you also call an axiom written on the page the axiom' and the axiom in your head 'the axiom'? After all, paper isn't a bunch of neurons, and you are a materialist after all...==&lt;br /&gt;
&lt;br /&gt;
Ah, but you forget something else: Abstract entities written on a page have no meaning in and of themselves. They are interactive phenomena - a sentient brain is required to interpret them and provide them with 'meaning'. Thus, when we say that the number &amp;quot;eighteen&amp;quot; is written on a page, what materialists are really saying is that this sensory input'18' through some social convention (some rule), yields the same firing of neurons in my brain as someone else's (more or less), which then become emergent phenomenon such as &amp;quot;abstract concepts&amp;quot; to our consciousnesses. &lt;br /&gt;
&lt;br /&gt;
A word written on a page and the same word spoken and traveling as a wave through the air are not 'the same matter'. However, when I read the word, and when I hear the word, my brain eventually interprets them the same way, producing similar electrochemical responses with enough fidelity that slightly different brains can reproduce the same abstraction, based on the same rules.&lt;br /&gt;
&lt;br /&gt;
Of course, the mapping itself is completely arbitrary. Our written alphabet needn't be what it is, and we could choose totally different symbols to represent the same thing as the spoken word.&lt;br /&gt;
&lt;br /&gt;
==Common Responses==&lt;br /&gt;
&lt;br /&gt;
The Identity of Indiscernibles is usually formulated as follows: if, for every property F, object x has F if and only if object y has F, then x is identical to y. Or in the notation of symbolic logic:&lt;br /&gt;
&lt;br /&gt;
∀F(Fx ↔ Fy) → x=y.&lt;br /&gt;
&lt;br /&gt;
This formula can be used to demonstrate that if x shares the same properties of y, then x and y are the same entity.&lt;br /&gt;
&lt;br /&gt;
The argument continues:&lt;br /&gt;
&lt;br /&gt;
A material entity cannot be in more than one spatio-temporal location at the same time.&lt;br /&gt;
&lt;br /&gt;
Response: This claim confuses fails to consider that abstractions are tokens or representations - formed in neurons by the same set of rules. However, the claim is doubly false, for even if we presume that abstractions are in fact the same identical entity, quantum physics tells us that there is no contradiction in having the same material entity in more than one spatio-temporal location:&lt;br /&gt;
&lt;br /&gt;
http://www.fizyka.umk.pl/~jkob/physnews/node30.html &lt;br /&gt;
&lt;br /&gt;
For more in the principle of Identity of indiscernibles and Liebnitz' transposition of the principle, the law of Indiscernability of Identicals, see here:&lt;br /&gt;
&lt;br /&gt;
http://plato.stanford.edu/entries/identity-indiscernible/#Rec&lt;/div&gt;</description>
			<pubDate>Sun, 11 Mar 2012 06:59:28 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:How_Does_A_Materialist_Account_for_Logic%3F</comments>		</item>
		<item>
			<title>MediaWiki:Sidebar</title>
			<link>http://72.14.177.54/logic/MediaWiki:Sidebar</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;* navigation&lt;br /&gt;
** mainpage|mainpage&lt;br /&gt;
** Course in Logic 101|Course in Logic 101 &lt;br /&gt;
** The Laws of Classical Logic|The Laws of Classical Logic  &lt;br /&gt;
** Validity, Strength, Soundness and Cogency|Validity, Strength, Soundness and Cogency &lt;br /&gt;
** Deductive and Inductive Logic|Deductive and Inductive Logic &lt;br /&gt;
** Logical Fallacies|Logical Fallacies &lt;br /&gt;
** Informal Fallacies|Informal Fallacies &lt;br /&gt;
** Formal Fallacies|Formal Fallacies &lt;br /&gt;
** Categorical Propositions|Categorical Propositions &lt;br /&gt;
** Classical Logic|Classical Logic &lt;br /&gt;
** Propositional Logic|Propositional Logic &lt;br /&gt;
** Predicate Logic|Predicate Logic &lt;br /&gt;
** Inductive Logic|Inductive Logic &lt;br /&gt;
** Metalogic|Metalogic&lt;br /&gt;
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			<pubDate>Thu, 25 Sep 2008 16:27:26 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/MediaWiki_talk:Sidebar</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* Necessity and Contingency */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. The universe isn't subject to any laws of logic at all. The universe merely exists.  However, because I feel there is a clear relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of the Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our ''syllogisms'' rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A metaphysical law of identity would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A is true, then A is true!&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary in the first place: the axioms of classical logic are held to be ''self evident''. We hold that they are are self evident because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely upon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the Stolen concept fallacy. See the [[Informal Logic]] section for more on this.&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[Axioms|axioms]]  be further advanced if the concepts of [[Necessity and Contingency|necessity]] and [[Necessity and Contingency|contingency]] are introduced. A [[proposition]] is said to be a '''necessary proposition''' if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[Necessity and Contingency|necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A proposition is said to be a '''contingent proposition''' if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propositional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
Greg Lopez writes that:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
the so-called &amp;quot;laws of logic&amp;quot; are not necessary to create an axiomatic formal logic: they are, however, derivable theorems of certain systems. Such systems which do not assume the &amp;quot;laws of logic&amp;quot; can be found in E. Mendelson's &amp;quot;Introduction to Mathematical Logic,&amp;quot; as well as S.C. Kleene's &amp;quot;Mathematical Logic.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
To be clear, I freely admit that the axioms and rules of inference for both of these systems were designed so as to imply the &amp;quot;laws of logic.&amp;quot; I still disagree with assertions, however, that these laws are fundamental axioms to all logical thought, and need not be defended or proposed as such. &lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[The Law of Noncontradiction|Law of Noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[Propositional Logic]]. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Lopez, G. &amp;quot;Where are the Laws of Thought&amp;quot; Retrieved from the World Wide Web on June 18, 2007&lt;br /&gt;
http://www.infidelguy.com/forumarchives/modules.php?name=Boards&amp;amp;file=viewtopic&amp;amp;t=5581&amp;amp;start=10&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:50:46 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* Necessity and Contingency */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. The universe isn't subject to any laws of logic at all. The universe merely exists.  However, because I feel there is a clear relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of the Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our ''syllogisms'' rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A metaphysical law of identity would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A is true, then A is true!&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary in the first place: the axioms of classical logic are held to be ''self evident''. We hold that they are are self evident because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely upon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the Stolen concept fallacy. See the [[Informal Logic]] section for more on this.&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[Axiom|axioms]]  be further advanced if the concepts of [[Necessity and Contingency|necessity]] and [[Necessity and Contingency|contingency]] are introduced. A [[proposition]] is said to be a '''necessary proposition''' if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A proposition is said to be a '''contingent proposition''' if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propositional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
Greg Lopez writes that:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
the so-called &amp;quot;laws of logic&amp;quot; are not necessary to create an axiomatic formal logic: they are, however, derivable theorems of certain systems. Such systems which do not assume the &amp;quot;laws of logic&amp;quot; can be found in E. Mendelson's &amp;quot;Introduction to Mathematical Logic,&amp;quot; as well as S.C. Kleene's &amp;quot;Mathematical Logic.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
To be clear, I freely admit that the axioms and rules of inference for both of these systems were designed so as to imply the &amp;quot;laws of logic.&amp;quot; I still disagree with assertions, however, that these laws are fundamental axioms to all logical thought, and need not be defended or proposed as such. &lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[The Law of Noncontradiction|Law of Noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[Propositional Logic]]. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Lopez, G. &amp;quot;Where are the Laws of Thought&amp;quot; Retrieved from the World Wide Web on June 18, 2007&lt;br /&gt;
http://www.infidelguy.com/forumarchives/modules.php?name=Boards&amp;amp;file=viewtopic&amp;amp;t=5581&amp;amp;start=10&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:49:59 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. The universe isn't subject to any laws of logic at all. The universe merely exists.  However, because I feel there is a clear relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of the Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our ''syllogisms'' rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A metaphysical law of identity would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A is true, then A is true!&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary in the first place: the axioms of classical logic are held to be ''self evident''. We hold that they are are self evident because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely upon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the Stolen concept fallacy. See the [[Informal Logic]] section for more on this.&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[axiom]]s can be further advanced if the concepts of [[Necessity and Contingency|necessity]] and [[Necessity and Contingency|contingency]] are introduced. A [[proposition]] is said to be a '''necessary proposition''' if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A [[proposition]] is said to be a [[contingent]] [[proposition]] if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propositional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
Greg Lopez writes that:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
the so-called &amp;quot;laws of logic&amp;quot; are not necessary to create an axiomatic formal logic: they are, however, derivable theorems of certain systems. Such systems which do not assume the &amp;quot;laws of logic&amp;quot; can be found in E. Mendelson's &amp;quot;Introduction to Mathematical Logic,&amp;quot; as well as S.C. Kleene's &amp;quot;Mathematical Logic.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
To be clear, I freely admit that the axioms and rules of inference for both of these systems were designed so as to imply the &amp;quot;laws of logic.&amp;quot; I still disagree with assertions, however, that these laws are fundamental axioms to all logical thought, and need not be defended or proposed as such. &lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[The Law of Noncontradiction|Law of Noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[Propositional Logic]]. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Lopez, G. &amp;quot;Where are the Laws of Thought&amp;quot; Retrieved from the World Wide Web on June 18, 2007&lt;br /&gt;
http://www.infidelguy.com/forumarchives/modules.php?name=Boards&amp;amp;file=viewtopic&amp;amp;t=5581&amp;amp;start=10&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:49:07 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. The universe isn't subject to any laws of logic at all. The universe merely exists.  However, because I feel there is a clear relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of the Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our syllogisms rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A [[metaphysical law of identity]] would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A, then A.&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary: the axioms of classical logic are held to be [[self evident]]. We hold that they are are [[self evident]] because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely upon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the [[Stolen concept fallacy]].&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[axiom]]s can be further advanced if the concepts of [[necessity]] and [[contingency]] are introduced. A [[proposition]] is said to be a [[necessary]] [[proposition]] if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A [[proposition]] is said to be a [[contingent]] [[proposition]] if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propositional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
Greg Lopez writes that:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
the so-called &amp;quot;laws of logic&amp;quot; are not necessary to create an axiomatic formal logic: they are, however, derivable theorems of certain systems. Such systems which do not assume the &amp;quot;laws of logic&amp;quot; can be found in E. Mendelson's &amp;quot;Introduction to Mathematical Logic,&amp;quot; as well as S.C. Kleene's &amp;quot;Mathematical Logic.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
To be clear, I freely admit that the axioms and rules of inference for both of these systems were designed so as to imply the &amp;quot;laws of logic.&amp;quot; I still disagree with assertions, however, that these laws are fundamental axioms to all logical thought, and need not be defended or proposed as such. &lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the &lt;br /&gt;
universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[Law of Noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[Propositional Logic]]. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Lopez, G. &amp;quot;Where are the Laws of Thought&amp;quot; Retrieved from the World Wide Web on June 18, 2007&lt;br /&gt;
http://www.infidelguy.com/forumarchives/modules.php?name=Boards&amp;amp;file=viewtopic&amp;amp;t=5581&amp;amp;start=10&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:45:16 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. The universe isn't subject to any laws of logic at all. The universe merely exists.  However, because I feel there is a clear relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of the Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our syllogisms rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A [[metaphysical law of identity]] would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A, then A.&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary: the axioms of classical logic are held to be [[self evident]]. We hold that they are are [[self evident]] because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely upon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the [[Stolen concept fallacy]].&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[axiom]]s can be further advanced if the concepts of [[necessity]] and [[contingency]] are introduced. A [[proposition]] is said to be a [[necessary]] [[proposition]] if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A [[proposition]] is said to be a [[contingent]] [[proposition]] if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propositional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
Greg Lopez writes that:&lt;br /&gt;
&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
the so-called &amp;quot;laws of logic&amp;quot; are not necessary to create an axiomatic formal logic: they are, however, derivable theorems of certain systems. Such systems which do not assume the &amp;quot;laws of logic&amp;quot; can be found in E. Mendelson's &amp;quot;Introduction to Mathematical Logic,&amp;quot; as well as S.C. Kleene's &amp;quot;Mathematical Logic.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
To be clear, I freely admit that the axioms and rules of inference for both of these systems were designed so as to imply the &amp;quot;laws of logic.&amp;quot; I still disagree with assertions, however, that these laws are fundamental axioms to all logical thought, and need not be defended or proposed as such. &lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the &lt;br /&gt;
universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[law of noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[propositional]] logic. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Lopez, G. &amp;quot;Where are the Laws of Thought&amp;quot; Retrieved from the World Wide Web on June 18, 2007&lt;br /&gt;
http://www.infidelguy.com/forumarchives/modules.php?name=Boards&amp;amp;file=viewtopic&amp;amp;t=5581&amp;amp;start=10&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:43:30 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. The universe isn't subject to any laws of logic at all. The universe merely exists.  However, because I feel there is a clear relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of the Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our syllogisms rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A [[metaphysical law of identity]] would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A, then A.&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary: the axioms of classical logic are held to be [[self evident]]. We hold that they are are [[self evident]] because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely opon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the [[Stolen concept fallacy]].&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[axiom]]s can be further advanced if the concepts of [[necessity]] and [[contingency]] are introduced. A [[proposition]] is said to be a [[necessary]] [[proposition]] if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A [[proposition]] is said to be a [[contingent]] [[proposition]] if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propostional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the &lt;br /&gt;
universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[law of noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[propositional]] logic. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:41:00 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
		<item>
			<title>Rertortion</title>
			<link>http://72.14.177.54/logic/Rertortion</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Defense through retortion occurs whenever one is forced to rely upon the very concept one is seeking to refute, it order to refute it. See 'Stealing the Concept&amp;quot; in the [[Informal Fallacies]] section.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:32:30 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Rertortion</comments>		</item>
		<item>
			<title>The Law of Noncontradiction</title>
			<link>http://72.14.177.54/logic/The_Law_of_Noncontradiction</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
The Law of Noncontradiction is defended through [[Rertortion|retortion]]: any attempt to contradict the concept must rely on the acceptance that contradictions are false.&lt;br /&gt;
&lt;br /&gt;
It can be proven using [[Propositional Logic]]:&lt;br /&gt;
&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
The Law of Noncontradiction, while appearing prima facie and necessarily true, is questioned by modern logicians. See [[Paraconsistent Logic]] and [[Dialetheism]].&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:25:58 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Noncontradiction</comments>		</item>
		<item>
			<title>The Law of Noncontradiction</title>
			<link>http://72.14.177.54/logic/The_Law_of_Noncontradiction</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
The Law of Noncontradiction can be proven using [[Propositional Logic]]:&lt;br /&gt;
&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:23:50 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Noncontradiction</comments>		</item>
		<item>
			<title>Indeterminate</title>
			<link>http://72.14.177.54/logic/Indeterminate</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;A reason for postulating a third truth-value 'indeterminate' is the problem of vagueness. Vagueness exists in the real world, because the real world is not a set of discrete catergories - it is a continuum. Therefore, attempts to apply deductive logic to the real world are always as imperfect as attempts to apply geometrical patterns like squares and circles to a world filled with ovals and rectangles.&lt;br /&gt;
&lt;br /&gt;
Consider a color spectrum between red and orange. Let us also call the statement, 'It is red here', 'p'. Now, it is obvious that there are &amp;quot;clear enough&amp;quot; cases where 'p' is true (the red case) and &amp;quot;clear enough&amp;quot; cases where 'p' is false (the orange case). However, between the two extremes there seems to be a large class of colors where we just cannot say whether 'p' is true or false. Hence, some have suggested that in such cases 'p' is neither true nor false and that a third truth-value — indeterminate — is needed. Such a suggestion would rule out bivalence but retain the law of excluded middle. The best book on this distinction and the problem of vagueness is Timothy Williamson's book Vagueness.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:22:57 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Indeterminate</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. Because of the relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of the Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our syllogisms rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A [[metaphysical law of identity]] would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A, then A.&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary: the axioms of classical logic are held to be [[self evident]]. We hold that they are are [[self evident]] because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely opon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the [[Stolen concept fallacy]].&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[axiom]]s can be further advanced if the concepts of [[necessity]] and [[contingency]] are introduced. A [[proposition]] is said to be a [[necessary]] [[proposition]] if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A [[proposition]] is said to be a [[contingent]] [[proposition]] if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propostional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the &lt;br /&gt;
universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[law of noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[propositional]] logic. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:21:42 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
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			<title>Law of the Excluded Middle</title>
			<link>http://72.14.177.54/logic/Law_of_the_Excluded_Middle</link>
			<description>&lt;p&gt;Admin:&amp;#32;Law of the Excluded Middle moved to The Law of the Excluded Middle: Correct a fuckup&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;#redirect [[The Law of the Excluded Middle]]&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:19:59 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Law_of_the_Excluded_Middle</comments>		</item>
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			<title>The Law of the Excluded Middle</title>
			<link>http://72.14.177.54/logic/The_Law_of_the_Excluded_Middle</link>
			<description>&lt;p&gt;Admin:&amp;#32;Law of the Excluded Middle moved to The Law of the Excluded Middle&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; &lt;br /&gt;
&lt;br /&gt;
We can denote this law symbolically:&lt;br /&gt;
&lt;br /&gt;
P ∨ ¬P&amp;quot; (&amp;quot;P or not-P&amp;quot;)&lt;br /&gt;
&lt;br /&gt;
Example:&lt;br /&gt;
&lt;br /&gt;
For example, if P is the proposition:&lt;br /&gt;
&lt;br /&gt;
''Socrates is mortal''.&lt;br /&gt;
&lt;br /&gt;
then the law of excluded middle holds that the logical disjunction:&lt;br /&gt;
&lt;br /&gt;
''Either Socrates is mortal or Socrates is not mortal''.&lt;br /&gt;
&lt;br /&gt;
is true by virtue of its form alone. I.e. it is tautologous.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==Bivalence and The Law of The Excluded Middle==&lt;br /&gt;
&lt;br /&gt;
The principle of bivalence states that &lt;br /&gt;
&lt;br /&gt;
''every proposition is either true or false'' &lt;br /&gt;
&lt;br /&gt;
and the law of excluded middle states:&lt;br /&gt;
&lt;br /&gt;
''p or not-p''. &lt;br /&gt;
&lt;br /&gt;
It is important to see that these two principles are stating entirely different things. Bivalence holds that that there are only two truth-values i.e. true and false. The Law of Excluded middle, on the other hand, is consistent with logics such as Fuzzy Logic which hold that there are more than two truth-values i.e. true, false and indeterminate. &lt;br /&gt;
&lt;br /&gt;
To see this, consider that 'p' means 'it is true that p' but 'not-p' means 'it is not true that p' from which it does not immediately follow that 'p is false' as p could also be [[Indeterminate]], at least within a supervalued logical framework.  &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:19:59 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_the_Excluded_Middle</comments>		</item>
		<item>
			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to basic laws of metaphysics&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments. Because of the relationship between the metaphysical status of these concepts and their application to logic, I will address both concepts in my definitions.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our syllogisms rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A [[metaphysical law of identity]] would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A, then A.&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary: the axioms of classical logic are held to be [[self evident]]. We hold that they are are [[self evident]] because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely opon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the [[Stolen concept fallacy]].&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[axiom]]s can be further advanced if the concepts of [[necessity]] and [[contingency]] are introduced. A [[proposition]] is said to be a [[necessary]] [[proposition]] if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A [[proposition]] is said to be a [[contingent]] [[proposition]] if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propostional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the &lt;br /&gt;
universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[law of noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[propositional]] logic. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
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		<item>
			<title>Indeterminate</title>
			<link>http://72.14.177.54/logic/Indeterminate</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;A reason for postulating a third truth-value 'indeterminate' is the problem of vagueness. Vagueness exists in the real world, because the real world is not a set of discrete catergories - it is a continuum. Therefore, attempts to apply deductive logic to the real world are always as imperfect as attempts to apply geometrical patterns like squares and circles to a world filled with ovals and rectangles.&lt;br /&gt;
&lt;br /&gt;
Consider a color spectrum between red and orange. Let us also call the statement, 'It is red here', 'p'. Now, it is obvious that there are cases where 'p' is true (the red case) and clear cases where 'p' is false (the orange case). However, between the two extremes there seems to be a large class of colours where we just cannot say whether 'p' is true or false. Hence, some have suggested that in such cases 'p' is neither true nor false and that a third truth-value — indeterminate — is needed. Such a suggestion would rule out bivalence but retain the law of excluded middle. The best book on this distinction and the problem of vagueness is Timothy Williamson's book Vagueness.&lt;/div&gt;</description>
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		<item>
			<title>The Law of the Excluded Middle</title>
			<link>http://72.14.177.54/logic/The_Law_of_the_Excluded_Middle</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; &lt;br /&gt;
&lt;br /&gt;
We can denote this law symbolically:&lt;br /&gt;
&lt;br /&gt;
P ∨ ¬P&amp;quot; (&amp;quot;P or not-P&amp;quot;)&lt;br /&gt;
&lt;br /&gt;
Example:&lt;br /&gt;
&lt;br /&gt;
For example, if P is the proposition:&lt;br /&gt;
&lt;br /&gt;
''Socrates is mortal''.&lt;br /&gt;
&lt;br /&gt;
then the law of excluded middle holds that the logical disjunction:&lt;br /&gt;
&lt;br /&gt;
''Either Socrates is mortal or Socrates is not mortal''.&lt;br /&gt;
&lt;br /&gt;
is true by virtue of its form alone. I.e. it is tautologous.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==Bivalence and The Law of The Excluded Middle==&lt;br /&gt;
&lt;br /&gt;
The principle of bivalence states that &lt;br /&gt;
&lt;br /&gt;
''every proposition is either true or false'' &lt;br /&gt;
&lt;br /&gt;
and the law of excluded middle states:&lt;br /&gt;
&lt;br /&gt;
''p or not-p''. &lt;br /&gt;
&lt;br /&gt;
It is important to see that these two principles are stating entirely different things. Bivalence holds that that there are only two truth-values i.e. true and false. The Law of Excluded middle, on the other hand, is consistent with logics such as Fuzzy Logic which hold that there are more than two truth-values i.e. true, false and indeterminate. &lt;br /&gt;
&lt;br /&gt;
To see this, consider that 'p' means 'it is true that p' but 'not-p' means 'it is not true that p' from which it does not immediately follow that 'p is false' as p could also be [[Indeterminate]], at least within a supervalued logical framework.  &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
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		<item>
			<title>The Law of the Excluded Middle</title>
			<link>http://72.14.177.54/logic/The_Law_of_the_Excluded_Middle</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; &lt;br /&gt;
&lt;br /&gt;
We can denote this law symbolically:&lt;br /&gt;
&lt;br /&gt;
P ∨ ¬P&amp;quot; (&amp;quot;P or not-P&amp;quot;)&lt;br /&gt;
&lt;br /&gt;
Example:&lt;br /&gt;
&lt;br /&gt;
For example, if P is the proposition:&lt;br /&gt;
&lt;br /&gt;
''Socrates is mortal''.&lt;br /&gt;
&lt;br /&gt;
then the law of excluded middle holds that the logical disjunction:&lt;br /&gt;
&lt;br /&gt;
''Either Socrates is mortal or Socrates is not mortal''.&lt;br /&gt;
&lt;br /&gt;
is true by virtue of its form alone. I.e. it is tautologous.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
The distinction between the principle of Bivalence and the Law of Excluded middle can be difficult to&lt;br /&gt;
understand — even the Oxford Companion to Philosophy conflates them. In classical logic the two&lt;br /&gt;
seem equivalent, with bivalence stated as ''every proposition is either true or false'' and the law of excluded middle stated as ''p or not-p''. At first glance the two do seem equivalent but consider the following case: Bivalence means that there are only two truth-values i.e. true and false. The Law of Excluded middle, on the other hand, is consistent with 'supervalued' logics such as Fuzzy Logic&lt;br /&gt;
where there are more than two truth-values i.e. true, false and indeterminate. To see this, consider&lt;br /&gt;
that 'p' means 'it is true that p' but 'not-p' means 'it is not true that p' from which it does not&lt;br /&gt;
immediately follow that 'p is false' as p could also be indeterminate, at least within a supervalued&lt;br /&gt;
logical framework. Of course, once you have the principle of bivalence, you can derive the law of&lt;br /&gt;
excluded middle but the opposite does not follow for the reason that the law of excluded middle is&lt;br /&gt;
consistent with three (or more) value logic as well as the principle of bivalence.&lt;br /&gt;
	&lt;br /&gt;
&lt;br /&gt;
A reason for postulating a third truth-value 'indeterminate' is the problem of vagueness. Consider a&lt;br /&gt;
colour spectrum between red and orange. Let us also call the statement, 'It is red here', 'p'. Now, it is obvious that there are cases where 'p' is true (the red case) and clear cases where 'p' is false (the orange case). However, between the two extremes there seems to be a large class of colours where we just cannot say whether 'p' is true or false. Hence, some have suggested that in such cases 'p' is neither true nor false and that a third truth-value — indeterminate — is needed. Such a suggestion would rule out bivalence but retain the law of excluded middle. The best book on this distinction and the problem of vagueness is Timothy Williamson's book Vagueness.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
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		<item>
			<title>Methods of Induction</title>
			<link>http://72.14.177.54/logic/Methods_of_Induction</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;John Stuart Mill is famed for his discourse on Induction. He gives us a system of discovering causes.&lt;br /&gt;
&lt;br /&gt;
http://www.humanpress.net/mill.jpg &lt;br /&gt;
&lt;br /&gt;
==Types of Causes==&lt;br /&gt;
&lt;br /&gt;
There are two general kinds of causes. A cause can be a sufficient condition or a necessary condition.&lt;br /&gt;
&lt;br /&gt;
A brick is a sufficient condition to break a window - not a necessary one, because other objects may break a window.&lt;br /&gt;
&lt;br /&gt;
A disruptive force is a necessary condition - it can be caused by a brick, or another heavy object, or pressure, or even vibration.&lt;br /&gt;
&lt;br /&gt;
==The Methods of Induction==&lt;br /&gt;
&lt;br /&gt;
Here now, are the various methods. Notice one more significant difference between logical methods and inductive methods - the following methodologies depend upon experimentation, rather than (solely) logical argument.&lt;br /&gt;
&lt;br /&gt;
===Direct Method of Agreement===&lt;br /&gt;
&lt;br /&gt;
This is a method of identifying a necessary cause. You examine all cases in which a given effect is present and try to find some factor, or putative cause, that is present in ALL of these cases. You eliminate all factors not present in these cases as possible causes. Any factor that remains is a candidate for necessary condition for the effect.&lt;br /&gt;
&lt;br /&gt;
===Inverse Method of Agreement===&lt;br /&gt;
&lt;br /&gt;
A method for identifying sufficient causes. Examine all cases in which a given effect, E, is absent and try to find some F that is also absent. Any factor that remains will be such that its nonpresence may be a necessary condition for the nonpresence of E.&lt;br /&gt;
&lt;br /&gt;
===Double Method===&lt;br /&gt;
&lt;br /&gt;
Combination of the two above methods.&lt;br /&gt;
&lt;br /&gt;
Shows both necessary and sufficient conditions.&lt;br /&gt;
&lt;br /&gt;
===Method of Difference===&lt;br /&gt;
&lt;br /&gt;
Examine two cases - one which exhibits the effect E, and one which does not. Try to find a single factor, F, that is present in the cases where E is present, and absent when E is not. This F is a candidate for a sufficient cause.&lt;br /&gt;
&lt;br /&gt;
===Joint Method of Agreement and Difference===&lt;br /&gt;
&lt;br /&gt;
Guess what this entails? A combination of the direct method (the first one listed) with the previous method, the method of difference. The factor revealed will be a strong candidate for a sufficient and necessary condition.&lt;br /&gt;
&lt;br /&gt;
===Method of Residues===&lt;br /&gt;
&lt;br /&gt;
Tough one to explain. In this one, you subtract known causal connections from other more complex (and known) casual relations, leaving as a candidate for a causal connection the remaining relation. If there is a causal connection between a complex or conjunctive event, called A and another event, called B, and if event a is an isolatable part of event A, and b is a likewise isolatable part of event B, and if there is a known causal relationship between a and b, then I can be concluded that there is a probable causal connection between the residue Aa and the residue Bb. It is difficult to assess from this point whether this is a sufficient or necessary cause.&lt;br /&gt;
&lt;br /&gt;
===Method of Concomitant Variation===&lt;br /&gt;
&lt;br /&gt;
Identify a functional relationship between a factor that admits of quantity or degree and an effect, E, that admits of quantity or degree, such that variations of F correspond (correlate) with variations in E. This may be a direct, or inverse relationship. Since this is a correlation, causality is only probabilistic - i.e. correlational data cannot link causality.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Hurely, P. J.  (2000) A Concise Introduction to Logic - 7th Edition&lt;/div&gt;</description>
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		<item>
			<title>Predicate Logic</title>
			<link>http://72.14.177.54/logic/Predicate_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* The New Square of Opposition */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;http://candleinthedark.com/drsmith_subject.jpg &amp;lt;BR&amp;gt;&lt;br /&gt;
In ''Predicate Logic'', the fundamental component of representation of propositions is the ''predicate''. We'll use capital letters to stand in for predicates. The letter W, for example, might stand for the predicate of being wise. With this symbolization, the proposition &amp;quot;Socrates is wise&amp;quot; would be represented as Ws. In general, we will uses the lower case letters of the alphabet, with the notable exceptions of x, y and z, to stand in for individuals. They are called individual constants.&lt;br /&gt;
&lt;br /&gt;
==The Conventions of Predicate Logic==&lt;br /&gt;
&lt;br /&gt;
The conventions of predicate logic use all the conventions found in propositional logic. For example, the proposition &amp;quot;If Socrates is wise, then Plato is wise&amp;quot; can be represented as Ws ⊃ Wp. And we use the variable &amp;quot;x&amp;quot;, symbolized in this case, as &amp;quot;Wx&amp;quot; as a place marker for any actual individual constant (like Socrates or Plato, usually proper names of individuals) so that a singular proposition might result.&lt;br /&gt;
&lt;br /&gt;
The various singular propositions Wa, Wb, Wc, have a bivalent truth function: either true or false, but &amp;quot;Wx&amp;quot;, as a propositional function, has an undetermined truth value until an actual constant is substituted. A propositional function is defined as an expression that contains an individual variable and becomes a statement when an individual constant (a, b, c...), is substituted for the individual variable. Such a situation can be called a substitution instance, and these substitutions are either true or false. We can call such proposition functions simple predicates: a proposition function having some true and some false substitution instances, each of which is an affirmative singular proposition.&lt;br /&gt;
&lt;br /&gt;
To review the symbolization of singular sentences&lt;br /&gt;
&lt;br /&gt;
 1. Individual constants: small letters a,b,c,...,w stand for a particular subject (named  &lt;br /&gt;
 individual). Ex. j=John, m=Mary, r=Rover&lt;br /&gt;
 2. Predicate letters: capital letters A,B,C,... stand for predicates. Ex. W=wise, I=Intelligent.&lt;br /&gt;
 3. Individual variables: small letters x,y,z stand for any small letter at all, any individual.&lt;br /&gt;
 4) Propositional functions: Ax, By, Pz stand for all sentences with a given predicate. Ex: Ax: x is&lt;br /&gt;
 in Australia; By: y is blue.&lt;br /&gt;
 5) Singular sentences: Aj, Bm, Pr symbolize particular sentences. Example: Einstein and Newton were&lt;br /&gt;
 geniuses. e = Einstein; n = Newton; G= Genius: Ge, Gn.&lt;br /&gt;
&lt;br /&gt;
==Quantification==&lt;br /&gt;
&lt;br /&gt;
As you may recall from earlier sections, [[George Boole]] uncovered the 'existential error&amp;quot; found within the Traditional Square, which reduce many of the previous mediate references that the Traditional Square allowed. The logician Frege created the concept of quantification to allow us to restore many of the traditions of the classical logicians - we'll see that the Traditional Square of Opposition will be nearly completely restored (only subalterns and superalterns will remain lost to us.) This process will allow us to create particular affirmative and negative propositions, and universal affirmative and negative propositions, just like in categorical logic.&lt;br /&gt;
&lt;br /&gt;
http://candleinthedark.com/frege.jpg&lt;br /&gt;
&lt;br /&gt;
===Universal Quantifier===&lt;br /&gt;
&lt;br /&gt;
The expressions &amp;quot;all&amp;quot;, &amp;quot;some&amp;quot;, &amp;quot;no&amp;quot; and &amp;quot;none&amp;quot;, are called quantifiers. Predicate logic contains symbols for two quantifiers, and they are nearly identical to the quantities in classical syllogistic logic. However, in Frege's theory, we can hold make a universal claim, without an existential error, by using the phrase &amp;quot;Given any X, X, has the characteristic of A&amp;quot; We can symbolize this thusly:&lt;br /&gt;
&lt;br /&gt;
(x) Ax&lt;br /&gt;
&lt;br /&gt;
Where &amp;quot;x&amp;quot; is the universal quantifier, and &amp;quot;A&amp;quot; is the specified characteristic. (Always place the variable in parentheses in front of the propositional function.)&lt;br /&gt;
&lt;br /&gt;
===Existential Quantifier===&lt;br /&gt;
&lt;br /&gt;
Recall from our discussion of the Traditional Square of Opposition that that propositions with a particular quantity have existential import - again, they assert that it is the case that at least one &amp;quot;x&amp;quot; exists. This is why the particular quantifier is referred to as the existential quantifier.&lt;br /&gt;
&lt;br /&gt;
Propositions with a particular quantity can be stated thusly: &amp;quot;There is at least one 'x', such that it has the character of A&amp;quot; We represent such propositions thusly:&lt;br /&gt;
&lt;br /&gt;
(∃ x)Ax&lt;br /&gt;
&lt;br /&gt;
Where &amp;quot;∃ &amp;quot; is the existential quantifier, and &amp;quot;A&amp;quot; again, is the specified characteristic.&lt;br /&gt;
&lt;br /&gt;
From what we have learned so far, propositions may be formed from propositional functions either by instantiation (substituting an individual constant for the individual variable) or by generalization (by placing a universal or existential quantifier before it.) It should be clear that the universal quantification is true only if all of its substitution instances are true, whereas the existential quantifier is true as long as there is at least one true substitution instance.&lt;br /&gt;
&lt;br /&gt;
==Quality==&lt;br /&gt;
&lt;br /&gt;
What about quality: affirmative and negative propositions? Well, in quantification theory, all we need do is add the &amp;quot;~' symbol before any predicate, to create universal negatives and particular negatives.&lt;br /&gt;
&lt;br /&gt;
Let's now take a look at some relationships between universal and existential quantification. The universal proposition of &amp;quot;Everyone is mortal&amp;quot; is denied by the existential proposition &amp;quot;Someone is not mortal&amp;quot;. These statements are symbolized as &amp;quot;(x)Mx&amp;quot; and &amp;quot;($x) ~Mx&amp;quot;, respectively. Since one is the denial of the other, we can negate one of them, and create the following true biconditionals:&lt;br /&gt;
&lt;br /&gt;
[~(x)Mx] [(∃ x)~Mx]&lt;br /&gt;
I.e: &amp;quot;It is not the case that everyone is mortal = There exists at least one person who is not mortal&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Or:&lt;br /&gt;
&lt;br /&gt;
[(x)Mx]≡ [(~∃x)~Mx]&lt;br /&gt;
i.e.: &amp;quot;Everyone is mortal = there isn't a case of someone who isn't mortal&amp;quot;&lt;br /&gt;
&lt;br /&gt;
If we use the capital letter &amp;quot;A&amp;quot; here as a variable, to represent any simple predicate, all the relationships between univeral and existential quantification can be symbolized here:&lt;br /&gt;
&lt;br /&gt;
 1) [(x)Ax]≡ [~(∃x)~Ax]&lt;br /&gt;
 2) [(∃x)Ax] ≡ [~(x)~Ax]&lt;br /&gt;
 3) [(x)~Ax]≡ [~(∃ x)Ax]&lt;br /&gt;
 4) [(∃x)~Ax] ≡ [~(x)Ax]&lt;br /&gt;
&lt;br /&gt;
We can express the above statements in words, thusly:&lt;br /&gt;
&lt;br /&gt;
 1) &amp;quot;Given any x, x has the characteristic of A&amp;quot; is equivalent to &amp;quot;There doesn't exist a case where &lt;br /&gt;
 an &amp;quot;x&amp;quot; doesn't have the characteristic of A&amp;quot;&lt;br /&gt;
 2) &amp;quot;There's at least one x with the characteristic of A&amp;quot; is equivalent to: &amp;quot;It's not the case that &lt;br /&gt;
 given any x, you'll find a case without the characteristic of A.&lt;br /&gt;
 3) &amp;quot;Given any x, none of them will have the character A&amp;quot; is equal to &amp;quot;There isn't a case of x with &lt;br /&gt;
 the characteristic of A&amp;quot;&lt;br /&gt;
 4) &amp;quot;It is the case that no X has the characteristic of A&amp;quot; is equal to &amp;quot;It is not the case that &lt;br /&gt;
 given any x, they will have the characteristic of A&amp;quot;&lt;br /&gt;
&lt;br /&gt;
Clever readers will realize that we are moving towards restoring the Traditional Square of Opposition. &lt;br /&gt;
&lt;br /&gt;
==The New Square of Opposition==  &lt;br /&gt;
&lt;br /&gt;
Using Univeral and Existential quantifiers, we now have, in a sense, a new Square of opposition, sans only super and sub alterns.&lt;br /&gt;
&lt;br /&gt;
http://candleinthedark.com/newsquare.jpg&lt;br /&gt;
&lt;br /&gt;
Continuing to assume the existence of at least one individual, we can say that:&lt;br /&gt;
&lt;br /&gt;
The two top propositions are contraries, they might both be false, but cannot both be true&lt;br /&gt;
The two bottom propositions are subcontraries, they might both be true, but both can't be false.&lt;br /&gt;
Propositions that are on the opposite end of the diaganols are contradictories: one must be true, and the other must be false.&lt;br /&gt;
Finally, on each side of the square, the truth of the lower proposition is implied by the truth directly above it. But we don't use the terms super and sub alterns.&lt;br /&gt;
&lt;br /&gt;
We can even recreate the traditional subject-predicate propositions of the Traditional Square, A, E, I and O:&lt;br /&gt;
&lt;br /&gt;
Consider four permutations on the phrase &amp;quot;All humans are mortal&amp;quot;&lt;br /&gt;
&lt;br /&gt;
 A (x)(Hx ⊃ Mx) - All humans are mortal&lt;br /&gt;
 E (x)(Hx ⊃ ~Mx) - No humans are mortal&lt;br /&gt;
 I (∃x)(Hx &amp;amp; Mx) - Some humans are mortal&lt;br /&gt;
 O (∃x)(Hx &amp;amp; ~Mx) - Some humans are not mortal &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] should proceed to the next section on [[Inductive Logic]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Hurely, P. J.  (2000) A Concise Introduction to Logic - 7th Edition&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 23:01:06 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Predicate_Logic</comments>		</item>
		<item>
			<title>Main Page</title>
			<link>http://72.14.177.54/logic/Main_Page</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* See also */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;==Introduction==&lt;br /&gt;
&lt;br /&gt;
This site is intended as a resource for those interested in learning Logic. While the author of this page will take a scholarly approach to the subject, this page will approach the subject in a more user friendly manner than available at Wikipedia, at times even using colloquial language. The site will offer a full [[Course in Logic 101]], based on two of the most reliable texts on logic: Copi and Cohen's ''Introduction to Logic (11th Edition)'' and Hurely's ''A Concise Introduction to Logic (7th Edition)''. The [[Course in Logic 101|course]] will cover the basics of Logic, [[Classical Logic]], [[Propositional Logic]], [[Predicate Logic]], [[Modal Logic]] and [[Inductive Logic]] including a discussion of [[Inductive Logic|Bayesian Theory]]. Those interested in taking the [[Course in Logic 101|course]] can consult that page for the proper order of reading the pages of this site.&lt;br /&gt;
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Now, let's begin.&lt;br /&gt;
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'''Logic''', (from the Greek word &amp;amp;lambda;&amp;amp;#972;&amp;amp;gamma;&amp;amp;omicron;&amp;amp;sigmaf; (''logos''), originally meaning ''the word'', but also referring to ''speech'' or ''reason'') is the science of evaluating the reasoning within [[Argument|arguments]].&lt;br /&gt;
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==Nature of logic==  &lt;br /&gt;
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Logic arose from a concern with correctness of [[argument]]ation (See [[Aristotle]]).  Logic is generally accepted and understood by logicians as a set of rules that tell us when an [[argument|argument's]] premises support their conclusion. Logic specifically deals with inferences whose validity can be traced back to the formal features of the representations that are involved in that inference.'' (Hofweber 2004).  &lt;br /&gt;
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Therefore, a further understanding of just what logic is, can be enhanced by delineating it from what it is not:&lt;br /&gt;
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*Logic is not the 'groundness of being' - that's metaphysics.&lt;br /&gt;
*Logic is not a set of laws that governs the universe - that's physics. &lt;br /&gt;
*Logic is not an immaterial &amp;quot;entity&amp;quot; that transcends reality - that's speculative theology.&lt;br /&gt;
*Logic is no a method for 'studying the world' -  that's science. &lt;br /&gt;
*Logic is not the method for assessing axioms - that's a matter of pure reason. &lt;br /&gt;
*Logic is not a way of evaluating 'truth' - that's philosophy. &lt;br /&gt;
*Logic is not a set of laws that governs human behavior - that's psychology. &lt;br /&gt;
*Logic is not even a study of how people reason - [[Non Logical Modes of Thought|Fortunately]] there is more to human reason than just logic.&lt;br /&gt;
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[[Immanuel Kant]] introduced an alternative idea as to what logic is.  He argued that logic should be conceived as the science of judgment, an idea taken up by [[Gottlob Frege]]. However, modern psychologists have demonstrated that a significant percentage of human judgment is clearly non logical.&lt;br /&gt;
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===Relation to other sciences===&lt;br /&gt;
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Closely related to logic is semantics, or the philosophy of language, which concerns the meaning of the words and sentences; epistemology, or the theory of knowledge, which concerns the conditions under which assertions are true; and the psychology of reasoning, which concerns the mental processes involved in reasoning.  Logic, however, is generally understood to describe reasoning in a prescriptive manner (i.e.  it describes how reasoning ought to take place), whereas psychology is descriptive and therefore more inclusive vis-a-vis the various methods of judgment humans actually use.  &lt;br /&gt;
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===Definition of an Argument===&lt;br /&gt;
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An [[argument]] is made up of a group  of statements we call [[proposition]]s. We use the term [[proposition]] instead of [[sentence]] because a proposition is more than just a sentence, it is a declarative sentence that contains a [[truth value]]. In the case of [[Classical Logic]], which is based on the [[Law of the Excluded Middle]], this truth value must  either be &amp;quot;true&amp;quot; or false&amp;quot; . &lt;br /&gt;
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There are two types of [[proposition]]s. The first, the [[Premises|Premise]], makes a commitment to truth, and is used as evidence to support the second type of proposition, the [[Conclusion]], which is the claim the arguer wants to prove. An argument must at least imply one of each. The study of logic, therefore, is the effort to determine the conditions under which one is justified in passing from the premises to the conclusion that logically must follow them.&lt;br /&gt;
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=== Examining Arguments: Informal, formal, and symbolic logic===&lt;br /&gt;
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Arguments can be examined through examining their premises, the form of the argument, and by looking at them abstractly. We use the terms &amp;quot;informal&amp;quot;, &amp;quot;formal&amp;quot; and &amp;quot;symbolic&amp;quot; to capture these meanings.&lt;br /&gt;
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* '''[[Formal and Informal Logic|Informal Logic]]''' is the study of natural language [[Argument|arguments]].  The study of fallacies is an especially important branch of informal logic.&lt;br /&gt;
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* '''[[Formal and Informal Logic|Formal Logic]]''' is the study of inference with purely formal content, where that content is made explicit. (An inference possesses a purely formal content if it can be expressed as a particular application of a wholly abstract rule, that is, a rule that is not about any particular thing or property.  We will see later that on many definitions of logic, logical inference and inference with purely formal content are the same thing.  This does not render the notion of informal logic vacuous, since one may wish to investigate logic without committing to a ''particular'' formal analysis.)&lt;br /&gt;
* '''[[Propositional Logic|Symbolic Logic]]''' is closely related to formal logic: it the study of symbolic abstractions that capture the formal features of logical inference.&lt;br /&gt;
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===Consistency, soundness, and completeness===&lt;br /&gt;
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There are three valuable properties that formal systems can have:&lt;br /&gt;
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:* '''[[Consistency]]''', which means that none of the theorems of the system contradict each other.&lt;br /&gt;
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:* '''[[Validity, Strength, Soundness and Cogency|Soundness]]''', which means that the system's rules of derivation will never let you infer anything false, so long as you start with only true premises.  So if a system is sound (and its axioms, if any, are true), then the theorems of a sound formal system are the [[truth]]s.  All of the theorems of a system that has no axioms are its truths and sometimes the truths of such a system are called 'logical truths.' (Note that if a system is not consistent, it cannot be sound. This is because a contradiction is always false, so if two theorems contradict at least one is false.)&lt;br /&gt;
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:* '''[[Completeness]]''', which means that there are no true sentences in the system that cannot, at least in principle, be proved using the derivation rules (and axioms, if any) of the system. &lt;br /&gt;
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Not all systems achieve all three virtues. It has been proven by [[Kurt Gödel]] that a system with enough axioms and/or rules of derivation to derive the principles of arithmetic cannot be both consistent and complete. This is called [[Gödel's Incompleteness Theorem]].&lt;br /&gt;
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===Deductive and inductive reasoning===&lt;br /&gt;
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Originally, logic consisted only of [[Deductive and Inductive Logic|deductive reasoning]] which concerns what follows universally from given premises.  However, it is important to note that [[Deductive and Inductive Logic|inductive reasoning]]&amp;amp;mdash;the study of deriving a reliable generalization from observations&amp;amp;mdash;has sometimes been included in the study of logic. Correspondingly, we must distinguish between deductive validity and inductive validity.  An inference is deductively valid if and only if there is no possible situation in which all the premises are true and the conclusion false.  The notion of deductive validity can be rigorously stated for systems of [[Formal and Informal Logic|formal logic]] in terms of the well-understood notions of [[semantics]].  Inductive validity on the other hand requires us to define a ''reliable generalization'' of some set of observations. The task of providing this definition may be approached  in various ways, some less formal than others; some of these definitions may use [[mathematical model]]s of probability.  For the most part this discussion of logic deals only with deductive logic.&lt;br /&gt;
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==Types of logic==&lt;br /&gt;
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Formal logic encompasses a wide variety of logical systems.  Various systems of logic include [[Classical Logic|Classical]] or [[Classical Logic|Syllogistic logic]], [[Predicate Logic]], [[Propositional Logic]], and [[Modal Logic]], and formal systems are indispensable in all branches of [[mathematical logic]].  &lt;br /&gt;
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===Syllogistic or Classical Logic===&lt;br /&gt;
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The ''Organon'' was [[Aristotle]]'s body of work on logic, with the ''Prior Analytics'' constituting the first explicit work in [[Formal and Informal Logic|formal logic]], introducing to the world the [[Syllogism|syllogism]]. [[Classical Logic|Syllogistic Logic]], [[Classical Logic|Term logic]], [[Classical Logic|Aristotelean Logic]] or [[Classical Logic]] are all references to the logical form of the [[Syllogism|syllogism]]. Syllogistic logic is the analysis of the judgments into propositions consisting of two terms that are related by one of a fixed number of relations, and the expression of inferences by means of [[syllogism]]s that consisted of two propositions sharing a common term as premise, and a conclusion which was a proposition involving the two unrelated terms from the premises.&lt;br /&gt;
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Aristotle's work was regarded in classical times and from medieval times in Europe and the Middle East as the very picture of a fully worked out system.  It was not alone: the [[Stoics]] proposed a system of [[Propositional Logic]] that was studied by medieval logicians; nor was the perfection of Aristotle's system undisputed; for example the [[problem of multiple generality]] was recognized in medieval times.  Nonetheless, problems with syllogistic logic were not seen as being in need of revolutionary solutions.&lt;br /&gt;
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Today, some academics claim that Aristotle's system is generally seen as having little more than historical value (though there is some current interest in extending term logics), regarded as made obsolete by the advent of [[Sentential Logic]] and the [[Predicate Logic|predicate calculus]].&lt;br /&gt;
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===Propositional Logic===&lt;br /&gt;
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Logic as it is studied today is a very different subject from [[Classical Logic]];  the principal difference is the innovation of [[Propositional Logic]] and [[Predicate Logic]]. Propositional Logic allows for more complex argument forms than classical syllogisms. In propositional logic, propositions are represented by ''symbols'' and ''connectors'', so that the statement's logical form can be assessed for cases of truth and falsity, which in turn allows us to assess the entire argument's form for validity or invalidity. In symbolic, or propositional logic, a simple statement, containing one proposition, is is referred to as an ''atomic statement'', and is symbolized by one letter, such as p. A compound statement, with more than one proposition holding some relationship to another proposition, is referred to as a molecular statement, which may be symbolized as p v q. The v symbol just used is a connective: Atomic propositions become molecular propositions when they are joined by connectives. &lt;br /&gt;
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===Predicate Logic===&lt;br /&gt;
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However, just as limits in Classical Logical led to [[Propositional Logic]], limits in Propositional Logic pointed to the need for a new logic. Propositional Logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument:&lt;br /&gt;
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    * All men are mortal&lt;br /&gt;
    * Socrates is a man&lt;br /&gt;
    * Therefore, Socrates is mortal&lt;br /&gt;
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into propositional logic yields&lt;br /&gt;
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    * A&lt;br /&gt;
    * B&lt;br /&gt;
    * ∴ C (∴ means &amp;quot;therefore&amp;quot;&lt;br /&gt;
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which is invalid, because there are no connectors between the premises and between the premises and the conclusion.&lt;br /&gt;
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Therefore, the need for a ''First Order'', or [[Predicate Logic]] became apparent. The new ingredient of first-order logic not found in propositional logic is [[Predicate Logic|quantification]]: where φ is any (well-formed) formula, the new constructions ∀x φ and ∃x φ — read &amp;quot;for all x, φ&amp;quot; and &amp;quot;for some x, φ&amp;quot; — are introduced, where x is an individual variable whose range is the set of individuals of some given universe of discourse (or domain). For example, if the universe consists solely of people, then x ranges over people. For convenience, we write φ as φ(x) to show that it contains only the variable x free and, for b a member of the universe, we let φ[b] express that b satisfies (i.e. has the property expressed by) φ. Then ∀x φ(x) states that φ[b] is true for every b in the universe, and ∃x φ(x) means that there is a b (in the universe) such that φ[b] holds.&lt;br /&gt;
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The argument about Socrates can be formalized in first-order logic as follows. Let the universe of discourse be the set of all people, living and deceased, and let Man(x) be a predicate (which, informally, means that the person represented by variable x is a man) and Mortal(x) be a second predicate. Then the argument above becomes&lt;br /&gt;
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    * ∀ x (Man(x) → Mortal(x))&lt;br /&gt;
    * Man(Socrates)&lt;br /&gt;
    * ∴ Mortal(Socrates)&lt;br /&gt;
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A literal translation of the first line would be &amp;quot;For all x, if x is described by 'Man', x must also be described by 'Mortal'.&amp;quot; The second line states that the predicate &amp;quot;Man&amp;quot; applies to Socrates, and the third line translates to &amp;quot;Therefore, the description 'Mortal' applies to Socrates.&amp;quot;&lt;br /&gt;
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===Modal logic===&lt;br /&gt;
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In language, [[modality]] deals with the phenomenon that subparts of a sentence may have their semantics modified by special verbs or modal particles.  For example, &amp;quot;''We go to the games''&amp;quot; can be modified to give &amp;quot;''We should go to the games''&amp;quot;, and &amp;quot;''We can go to the games''&amp;quot;&amp;quot; and perhaps &amp;quot;''We will go to the games''&amp;quot;.  More abstractly, we might say that modality affects the circumstances in which we take an assertion to be satisfied.&lt;br /&gt;
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The logical study of modality dates back to [[Aristotle]], who was concerned with the [[alethic modalities]] of necessity and possibility, which he observed to be dual in the sense of [[De Morgan duality]].  While the study of necessity and possibility remained important to philosophers, little logical innovation happened until the landmark investigations of [[Clarence Irving Lewis]] in [[1918]], who formulated a family of rival axiomatisations of the alethic modalities.  His work unleashed a torrent of new work on the topic, expanding the kinds of modality treated to include [[deontic logic]] and [[epistemic logic]].  The seminal work of [[Arthur Prior]] applied the same formal language to treat [[temporal logic]] and paved the way for the marriage of the two subjects.  [[Saul Kripke]] discovered (contemporaneously with rivals) his theory of [[frame semantics]] which revolutionized the formal technology available to modal logicians and gave a new [[graph theory|graph-theoretic]] way of looking at modality that has driven many applications in [[computational linguistics]] and [[computer science]], such as [[dynamic logic]].&lt;br /&gt;
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Students following the [[Course in Logic 101]] should proceed to the section entitled: [[The Laws of Classical Logic]]&lt;br /&gt;
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==References==&lt;br /&gt;
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* Copi, I. M, Cohen, C., (2001), ''Introduction to Logic'', 11th Edition.&lt;br /&gt;
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* Gabbay, D.M., and Guenthner, F. (eds., 2001-2005), ''Handbook of Philosophical Logic'', 13 vols., 2nd edition, Kluwer Publishers, Dordrecht.&lt;br /&gt;
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* Hilbert, D., and Ackermann, W. (1928), ''Grundzüge der theoretischen Logik'' (''Principles of Theoretical Logic''), Springer-Verlag.&lt;br /&gt;
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* Hodges, W. (2001), ''Logic.  An introduction to Elementary Logic'', Penguin Books.&lt;br /&gt;
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* Hofweber, T. (2004), &amp;quot;Logic and Ontology&amp;quot;, ''Stanford Encyclopedia of Philosophy'', Edward N. Zalta (ed.), [http://plato.stanford.edu/entries/logic-ontology/ Eprint].&lt;br /&gt;
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* Hughes, R.I.G. (ed., 1993), ''A Philosophical Companion to First-Order Logic'', Hackett Publishing.&lt;br /&gt;
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* Hurely, P. J.  (2000) ''A Concise Introduction to Logic'' - 7th Edition&lt;br /&gt;
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* Kneale, W., and Kneale, M., (1962), ''The Development of Logic'', Oxford University Press, London, UK.&lt;br /&gt;
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* Priest, G. (2004), &amp;quot;Dialetheism&amp;quot;, ''Stanford Encyclopedia of Philosophy'', Edward N. Zalta (ed.), [http://plato.stanford.edu/entries/dialetheism Eprint].&lt;br /&gt;
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==See also== &lt;br /&gt;
* [[Course in Logic 101]] This takes the interested reader to every major page of the site.&lt;br /&gt;
* [[The Laws of Classical Logic]]  This page presents the axioms of classical logic&lt;br /&gt;
* [[Validity, Strength, Soundness and Cogency ]]&lt;br /&gt;
* [[Deductive and Inductive Logic]]&lt;br /&gt;
* [[Fallacies|Logical Fallacies]]&lt;br /&gt;
* [[Informal Fallacies]]  This page presents a list of informal fallacies found in arguments.&lt;br /&gt;
* [[Formal Fallacies]] This page examines both valid and invalid logical forms.&lt;br /&gt;
* [[Categorical Propositions]] &lt;br /&gt;
* [[Classical Logic]]&lt;br /&gt;
* [[Propositional Logic]] &lt;br /&gt;
* [[Predicate Logic]]&lt;br /&gt;
* [[Inductive Logic]] &lt;br /&gt;
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[[Category:Logic]]&lt;br /&gt;
[[Category:Tutorials]]&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:58:52 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Main_Page</comments>		</item>
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			<title>Tautology</title>
			<link>http://72.14.177.54/logic/Tautology</link>
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&lt;div&gt;In [[Propositional Logic]], a '''tautology''' is a statement that is truth-functionally valid&amp;amp;mdash;i.e. it is universally true, or true in every interpretation).  For example, the statement &amp;quot;If it rains, then it rains&amp;quot; is a tautology. Every theorem of propositional logic is a tautology, and so we can equivalently define 'tautology' as any theorem of propositional logic&amp;amp;mdash;i.e. any statement that is deducible from the empty set in some system of deduction of propositional logic, such as a natural deduction system. The term is often mistakenly applied to any validity (or theorem) of [[first-order logic]], though it applies only to a proper subset of such validities. The term was originally introduced by [[Ludwig Wittgenstein]].&lt;br /&gt;
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The negation of a tautology is clearly a [[Contradiction|contradiction]], and the negation of a contradiction is clearly a tautology. A sentence that is neither a tautology (always true) nor a contradiction (always false) is logically [[Necessity and Contingency|contingent]], i.e., possible of being true or false .&lt;br /&gt;
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==Discovering tautologies==&lt;br /&gt;
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An effective procedure for checking whether a propositional formula is a tautology or not is by means of a [[Truth Tables|Truth Table]]  &lt;br /&gt;
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== References ==&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:54:57 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Tautology</comments>		</item>
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			<title>Tautology</title>
			<link>http://72.14.177.54/logic/Tautology</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
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&lt;div&gt;In [[Propositional Logic]], a '''tautology''' is a statement that is truth-functionally valid&amp;amp;mdash;i.e. it is universally true, or true in every interpretation).  For example, the statement &amp;quot;If it rains, then it rains&amp;quot; is a tautology. Every theorem of propositional logic is a tautology, and so we can equivalently define 'tautology' as any theorem of propositional logic&amp;amp;mdash;i.e. any statement that is deducible from the empty set in some system of deduction of propositional logic, such as a natural deduction system. The term is often mistakenly applied to any validity (or theorem) of [[first-order logic]], though it applies only to a proper subset of such validities. The term was originally introduced by [[Ludwig Wittgenstein]].&lt;br /&gt;
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The negation of a tautology is clearly a [[Contradiction]], and the negation of a contradiction is clearly a tautology. A sentence that is neither a tautology (always true) nor a contradiction (always false) is logically [[Necessity and Contingency|contingent]], i.e., possible of being true or false .&lt;br /&gt;
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==Discovering tautologies==&lt;br /&gt;
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An effective procedure for checking whether a propositional formula is a tautology or not is by means of a [[Truth Tables|Truth Table]]  &lt;br /&gt;
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== References ==&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:49:43 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Tautology</comments>		</item>
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			<title>Tautology</title>
			<link>http://72.14.177.54/logic/Tautology</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
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&lt;div&gt;In [[Popositional Logic]], a '''tautology''' is a [[statement]] that is truth-functionally valid&amp;amp;mdash;i.e. it is universally true, or true in every interpretation).  For example, the statement &amp;quot;If it rains, then it rains&amp;quot; is a tautology. Every theorem of propositional logic is a tautology, and so we can equivalently define 'tautology' as any theorem of propositional logic&amp;amp;mdash;i.e. any statement that is deducible from the empty set in some system of deduction of propositional logic, such as a [[natural deduction]] system. The term is often mistakenly applied to any validity (or theorem) of [[first-order logic]], though it applies only to a proper subset of such validities. The term was originally introduced by [[Ludwig Wittgenstein]].&lt;br /&gt;
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The negation of a tautology is clearly a [[Contradiction]], and the negation of a contradiction is clearly a tautology. A sentence that is neither a tautology (always true) nor a contradiction (always false) is logically [[Necessity and Contingency|contingent]], i.e., possible of being true or false .&lt;br /&gt;
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==Discovering tautologies==&lt;br /&gt;
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An effective procedure for checking whether a propositional formula is a tautology or not is by means of a [[Truth Tables|Truth Table]]  &lt;br /&gt;
 &lt;br /&gt;
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== References ==&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:48:46 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Tautology</comments>		</item>
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			<title>Tautology</title>
			<link>http://72.14.177.54/logic/Tautology</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
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&lt;div&gt;In [[Popositional Logic]], a '''tautology''' is a [[statement]] that is truth-functionally valid&amp;amp;mdash;i.e. it is universally true, or true in every interpretation).  For example, the statement &amp;quot;If it rains, then it rains&amp;quot; is a tautology. Every theorem of propositional logic is a tautology, and so we can equivalently define 'tautology' as any theorem of propositional logic&amp;amp;mdash;i.e. any statement that is deducible from the empty set in some system of deduction of propositional logic, such as a [[natural deduction]] system. The term is often mistakenly applied to any validity (or theorem) of [[first-order logic]], though it applies only to a proper subset of such validities. The term was originally introduced by [[Ludwig Wittgenstein]].&lt;br /&gt;
&lt;br /&gt;
The negation of a tautology is clearly a [[Contradiction]], and the negation of a contradiction is clearly a tautology. A sentence that is neither a tautology (always true) nor a contradiction (always false) is logically [[Necessity and Contingency|contingent]], i.e., possible of being true or false .&lt;br /&gt;
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== Tautologies versus validities ==&lt;br /&gt;
&lt;br /&gt;
The use of 'tautology', however, can be extended to [[first-order logic]] since it includes propositional logic. It can be further extended to include sentences that are quantified in the following sense. Call any statement that is not a truth-functional compound (i.e. not a conjunction, disjunction, conditional, etc.) a 'Boolean atom'. Then every [[atomic sentence]] is a Boolean atom, as is every quantified sentence&amp;amp;mdash;i.e. those of the form &amp;lt;math&amp;gt;\\forall x\\phi&amp;lt;/math&amp;gt; or &amp;lt;math&amp;gt;\\exists x\\phi&amp;lt;/math&amp;gt;. For example, &amp;lt;math&amp;gt;P(x)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;\\forall x(P(x)\\land Q(y))&amp;lt;/math&amp;gt; are Boolean atoms, while &amp;lt;math&amp;gt;\\forall xP(x)\\land Q(y)&amp;lt;/math&amp;gt; is not. Then a statement of first-order logic is a tautology if the uniform relettering of each of its Boolean atoms yields a tautology in the propositional sense. Thus &amp;lt;math&amp;gt;\\forall x(P(x) \\lor\\lnot P(x))&amp;lt;/math&amp;gt; is not a tautology, since its Boolean relettering yields &amp;lt;math&amp;gt;p&amp;lt;/math&amp;gt;, while &amp;lt;math&amp;gt;\\forall xP(x)\\lor\\lnot\\forall xP(x)&amp;lt;/math&amp;gt; is a tautology. One could further extend this notion by taking statements to be equivalence classes of statements, each of which is closed under the property of its elements being variants of each other (e.g. ''&amp;amp;forall;xP(x)'' is a variant of ''&amp;amp;forall;yP(y)'', and likewise upon substituting any other variable for ''x'' in the former). Then the Boolean relettering of &amp;lt;math&amp;gt;\\forall xP(x)\\lor\\lnot\\forall yP(y)&amp;lt;/math&amp;gt; yields a tautology, since each disjunct falls under the same equivalence class.&lt;br /&gt;
&lt;br /&gt;
==Discovering tautologies==&lt;br /&gt;
&lt;br /&gt;
An effective procedure for checking whether a propositional formula is a tautology or not is by means of a [[Truth Tables|Truth Table]]  &lt;br /&gt;
 &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
== References ==&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:44:48 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Tautology</comments>		</item>
		<item>
			<title>Tautology</title>
			<link>http://72.14.177.54/logic/Tautology</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;In [[Popositional Logic]], a '''tautology''' is a [[statement]] that is truth-functionally valid&amp;amp;mdash;i.e. it is universally true, or true in every interpretation).  For example, the statement &amp;quot;If it rains, then it rains&amp;quot; is a tautology. Every theorem of propositional logic is a tautology, and so we can equivalently define 'tautology' as any theorem of propositional logic&amp;amp;mdash;i.e. any statement that is deducible from the empty set in some system of deduction of propositional logic, such as a [[natural deduction]] system. The term is often mistakenly applied to any validity (or theorem) of [[first-order logic]], though it applies only to a proper subset of such validities. The term was originally introduced by [[Ludwig Wittgenstein]].&lt;br /&gt;
&lt;br /&gt;
The negation of a tautology is clearly a [[Contradiction]], and the negation of a contradiction is clearly a tautology. A sentence that is neither a tautology (always true) nor a contradiction (always false) is logically [[Necessity and Contingency|contingent]], i.e., possible of being true or false .&lt;br /&gt;
&lt;br /&gt;
== Tautologies versus validities ==&lt;br /&gt;
&lt;br /&gt;
The use of 'tautology', however, can be extended to [[first-order logic]] since it includes propositional logic. It can be further extended to include sentences that are quantified in the following sense. Call any statement that is not a truth-functional compound (i.e. not a conjunction, disjunction, conditional, etc.) a 'Boolean atom'. Then every [[atomic sentence]] is a Boolean atom, as is every quantified sentence&amp;amp;mdash;i.e. those of the form &amp;lt;math&amp;gt;\\forall x\\phi&amp;lt;/math&amp;gt; or &amp;lt;math&amp;gt;\\exists x\\phi&amp;lt;/math&amp;gt;. For example, &amp;lt;math&amp;gt;P(x)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;\\forall x(P(x)\\land Q(y))&amp;lt;/math&amp;gt; are Boolean atoms, while &amp;lt;math&amp;gt;\\forall xP(x)\\land Q(y)&amp;lt;/math&amp;gt; is not. Then a statement of first-order logic is a tautology if the uniform relettering of each of its Boolean atoms yields a tautology in the propositional sense. Thus &amp;lt;math&amp;gt;\\forall x(P(x) \\lor\\lnot P(x))&amp;lt;/math&amp;gt; is not a tautology, since its Boolean relettering yields &amp;lt;math&amp;gt;p&amp;lt;/math&amp;gt;, while &amp;lt;math&amp;gt;\\forall xP(x)\\lor\\lnot\\forall xP(x)&amp;lt;/math&amp;gt; is a tautology. One could further extend this notion by taking statements to be equivalence classes of statements, each of which is closed under the property of its elements being variants of each other (e.g. ''&amp;amp;forall;xP(x)'' is a variant of ''&amp;amp;forall;yP(y)'', and likewise upon substituting any other variable for ''x'' in the former). Then the Boolean relettering of &amp;lt;math&amp;gt;\\forall xP(x)\\lor\\lnot\\forall yP(y)&amp;lt;/math&amp;gt; yields a tautology, since each disjunct falls under the same equivalence class.&lt;br /&gt;
&lt;br /&gt;
==Discovering tautologies==&lt;br /&gt;
&lt;br /&gt;
An effective procedure for checking whether a propositional formula is a tautology or not is by means of a [[Truth Table]]  &lt;br /&gt;
 &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
== References ==&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:42:25 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Tautology</comments>		</item>
		<item>
			<title>The Law of Identity</title>
			<link>http://72.14.177.54/logic/The_Law_of_Identity</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;[[Aristotle]]'s Law of Identity   http://importanceofphilosophy.com/Graphics/Aristotle.gif&lt;br /&gt;
&lt;br /&gt;
For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
We can state this simply as ''A equals A''&lt;br /&gt;
&lt;br /&gt;
Or, in logical form., as:&lt;br /&gt;
&lt;br /&gt;
A ≡ A&lt;br /&gt;
&lt;br /&gt;
('≡' refers to &amp;quot;If and only if', meaning that if &amp;quot;A&amp;quot; is true, then &amp;quot;A&amp;quot; must be true)&lt;br /&gt;
&lt;br /&gt;
And the law of Identity is necessarily true. It is a [[Tautology|tautology]].&lt;br /&gt;
&lt;br /&gt;
Aristotle wrote on the necessity of the law being true, thusly:&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
&amp;quot;Now 'why a thing is itself' is a meaningless inquiry (for -- to give meaning to the question 'why' -- the fact or the '''existence of the thing must already be evident''''-e.g. that the moon is eclipsed-but the fact that a thing is itself is the single reason and the single cause to be given in answer to all such questions as why the man is man, or the musician musical', unless one were to answer 'because each thing is inseparable from itself, and its being one just meant this' this, however, is common to all things and is a short and easy way with the question).&amp;quot; - Metaphysics Book VII, Part 17&lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Metaphysically, we can say that everything that exists has a specific nature. Each entity exists as something in particular and not it's own negation or antithesis.&lt;br /&gt;
&lt;br /&gt;
Furthermore, we can say that existence necessitates identity: an 'entity without an identity' is a contradiction, an oxymoron. To lack identity is to not exist. To exist is to exist as something, and that means to exist with a particular identity.&lt;br /&gt;
&lt;br /&gt;
Each entity exists as something specific, its identity is particular, and it cannot exist as something else. An entity can have more than one characteristic, but any characteristic it has is a part of its identity. A car can be both blue and red, but not at the same time or not in the same respect. Whatever portion is blue cannot be red at the same time, in the same way. Half the car can be red, and the other half blue. But the whole car can't be both red and blue. These two traits, blue and red, each have single, particular identities.&lt;br /&gt;
&lt;br /&gt;
The concept of identity is important because it makes explicit that reality has a definite nature. Since it exists in a particular way, it has characteristics. Since reality has an identity, it is knowable. &lt;br /&gt;
&lt;br /&gt;
Finally, it is important to separate the logical law of identity from the metaphysical law: the universe exists and has an identity, but this in itself is not the 'law of identity', for the logical law to exist, a mind must glean it, [[a priori]].&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Landauer, J. &amp;amp; Rowlands J., (2001)&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:39:00 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Identity</comments>		</item>
		<item>
			<title>The Law of Identity</title>
			<link>http://72.14.177.54/logic/The_Law_of_Identity</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;[[Aristotle]]'s Law of Identity   http://importanceofphilosophy.com/Graphics/Aristotle.gif&lt;br /&gt;
&lt;br /&gt;
For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
We can state this simply as ''A equals A''&lt;br /&gt;
&lt;br /&gt;
Or, in logical form., as:&lt;br /&gt;
&lt;br /&gt;
A ≡ A&lt;br /&gt;
&lt;br /&gt;
('≡' refers to &amp;quot;If and only if', meaning that if &amp;quot;A&amp;quot; is true, then &amp;quot;A&amp;quot; must be true)&lt;br /&gt;
&lt;br /&gt;
And the law of Identity is necessarily true. It is a [[tautology]].&lt;br /&gt;
&lt;br /&gt;
Aristotle wrote on the necessity of the law being true, thusly:&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
&amp;quot;Now 'why a thing is itself' is a meaningless inquiry (for -- to give meaning to the question 'why' -- the fact or the '''existence of the thing must already be evident''''-e.g. that the moon is eclipsed-but the fact that a thing is itself is the single reason and the single cause to be given in answer to all such questions as why the man is man, or the musician musical', unless one were to answer 'because each thing is inseparable from itself, and its being one just meant this' this, however, is common to all things and is a short and easy way with the question).&amp;quot; - Metaphysics Book VII, Part 17&lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Metaphysically, we can say that everything that exists has a specific nature. Each entity exists as something in particular and not it's own negation or antithesis.&lt;br /&gt;
&lt;br /&gt;
Furthermore, we can say that existence necessitates identity: an 'entity without an identity' is a contradiction, an oxymoron. To lack identity is to not exist. To exist is to exist as something, and that means to exist with a particular identity.&lt;br /&gt;
&lt;br /&gt;
Each entity exists as something specific, its identity is particular, and it cannot exist as something else. An entity can have more than one characteristic, but any characteristic it has is a part of its identity. A car can be both blue and red, but not at the same time or not in the same respect. Whatever portion is blue cannot be red at the same time, in the same way. Half the car can be red, and the other half blue. But the whole car can't be both red and blue. These two traits, blue and red, each have single, particular identities.&lt;br /&gt;
&lt;br /&gt;
The concept of identity is important because it makes explicit that reality has a definite nature. Since it exists in a particular way, it has characteristics. Since reality has an identity, it is knowable. &lt;br /&gt;
&lt;br /&gt;
Finally, it is important to separate the logical law of identity from the metaphysical law: the universe exists and has an identity, but this in itself is not the 'law of identity', for the logical law to exist, a mind must glean it, [[a priori]].&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Landauer, J. &amp;amp; Rowlands J., (2001)&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:38:04 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Identity</comments>		</item>
		<item>
			<title>The Law of Identity</title>
			<link>http://72.14.177.54/logic/The_Law_of_Identity</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;[[Aristotle]]'s Law of Identity   http://importanceofphilosophy.com/Graphics/Aristotle.gif&lt;br /&gt;
&lt;br /&gt;
For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
We can state this simply as ''A equals A''&lt;br /&gt;
&lt;br /&gt;
Or, in logical form., as:&lt;br /&gt;
&lt;br /&gt;
A ≡ A&lt;br /&gt;
&lt;br /&gt;
('≡' refers to &amp;quot;If and only if', meaning that if &amp;quot;A&amp;quot; is true, then &amp;quot;A&amp;quot; must be true)&lt;br /&gt;
&lt;br /&gt;
Aristotle wrote on the necessity of the law being true, thusly:&lt;br /&gt;
&amp;lt;blockquote&amp;gt;&lt;br /&gt;
&amp;quot;Now 'why a thing is itself' is a meaningless inquiry (for -- to give meaning to the question 'why' -- the fact or the '''existence of the thing must already be evident''''-e.g. that the moon is eclipsed-but the fact that a thing is itself is the single reason and the single cause to be given in answer to all such questions as why the man is man, or the musician musical', unless one were to answer 'because each thing is inseparable from itself, and its being one just meant this' this, however, is common to all things and is a short and easy way with the question).&amp;quot; - Metaphysics Book VII, Part 17&lt;br /&gt;
&amp;lt;/blockquote&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Metaphysically, we can say that everything that exists has a specific nature. Each entity exists as something in particular and not it's own negation or antithesis.&lt;br /&gt;
&lt;br /&gt;
Furthermore, we can say that existence necessitates identity: an 'entity without an identity' is a contradiction, an oxymoron. To lack identity is to not exist. To exist is to exist as something, and that means to exist with a particular identity.&lt;br /&gt;
&lt;br /&gt;
Each entity exists as something specific, its identity is particular, and it cannot exist as something else. An entity can have more than one characteristic, but any characteristic it has is a part of its identity. A car can be both blue and red, but not at the same time or not in the same respect. Whatever portion is blue cannot be red at the same time, in the same way. Half the car can be red, and the other half blue. But the whole car can't be both red and blue. These two traits, blue and red, each have single, particular identities.&lt;br /&gt;
&lt;br /&gt;
The concept of identity is important because it makes explicit that reality has a definite nature. Since it exists in a particular way, it has characteristics. Since reality has an identity, it is knowable. &lt;br /&gt;
&lt;br /&gt;
Finally, it is important to separate the logical law of identity from the metaphysical law: the universe exists and has an identity, but this in itself is not the 'law of identity', for the logical law to exist, a mind must glean it, [[a priori]].&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Landauer, J. &amp;amp; Rowlands J., (2001)&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:37:15 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Identity</comments>		</item>
		<item>
			<title>The Law of Identity</title>
			<link>http://72.14.177.54/logic/The_Law_of_Identity</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Aristotle's Law of Identity   http://importanceofphilosophy.com/Graphics/Aristotle.gif&lt;br /&gt;
&lt;br /&gt;
For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
We can state this simply as ''A equals A''&lt;br /&gt;
&lt;br /&gt;
Or, in logical form., as:&lt;br /&gt;
&lt;br /&gt;
A ≡ A&lt;br /&gt;
&lt;br /&gt;
('≡' refers to &amp;quot;If and only if', meaning that if &amp;quot;A&amp;quot; is true, then &amp;quot;A&amp;quot; must be true)&lt;br /&gt;
&lt;br /&gt;
Metaphysically, we can say that everything that exists has a specific nature. Each entity exists as something in particular and not it's own negation or antithesis.&lt;br /&gt;
&lt;br /&gt;
Furthermore, we can say that existence necessitates identity: an 'entity without an identity' is a contradiction, an oxymoron. To lack identity is to not exist. To exist is to exist as something, and that means to exist with a particular identity.&lt;br /&gt;
&lt;br /&gt;
Each entity exists as something specific, its identity is particular, and it cannot exist as something else. An entity can have more than one characteristic, but any characteristic it has is a part of its identity. A car can be both blue and red, but not at the same time or not in the same respect. Whatever portion is blue cannot be red at the same time, in the same way. Half the car can be red, and the other half blue. But the whole car can't be both red and blue. These two traits, blue and red, each have single, particular identities.&lt;br /&gt;
&lt;br /&gt;
The concept of identity is important because it makes explicit that reality has a definite nature. Since it exists in a particular way, it has characteristics. Since reality has an identity, it is knowable. &lt;br /&gt;
&lt;br /&gt;
Finally, it is important to separate the logical law of identity from the metaphysical law: the universe exists and has an identity, but this in itself is not the 'law of identity', for the logical law to exist, a mind must glean it, [[a priori]].&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Landauer, J. &amp;amp; Rowlands J., (2001)&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:34:19 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Identity</comments>		</item>
		<item>
			<title>A priori</title>
			<link>http://72.14.177.54/logic/A_priori</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Pure reason. An a priori act is a mental act of abstraction that only requires sentience, and not any specific experience.  The axioms of existence and identity are necessary implications in any thought, and may be gleaned a priori.&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:30:32 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:A_priori</comments>		</item>
		<item>
			<title>The Law of Identity</title>
			<link>http://72.14.177.54/logic/The_Law_of_Identity</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Aristotle's Law of Identity   http://importanceofphilosophy.com/Graphics/Aristotle.gif&lt;br /&gt;
&lt;br /&gt;
For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
We can state this simply:&lt;br /&gt;
&lt;br /&gt;
A=A&lt;br /&gt;
&lt;br /&gt;
Or, in logical form:&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
Metaphysically, we can say that everything that exists has a specific nature. Each entity exists as something in particular and not it's own negation or antithesis.&lt;br /&gt;
&lt;br /&gt;
Existence necessitates identity: an entity without an identity is an oxymoron - to lack identity is to not possess any characteristics and to be a non existent. To exist is to exist as something, and that means to exist with a particular identity.&lt;br /&gt;
&lt;br /&gt;
Each entity exists as something specific, its identity is particular, and it cannot exist as something else. An entity can have more than one characteristic, but any characteristic it has is a part of its identity. A car can be both blue and red, but not at the same time or not in the same respect. Whatever portion is blue cannot be red at the same time, in the same way. Half the car can be red, and the other half blue. But the whole car can't be both red and blue. These two traits, blue and red, each have single, particular identities.&lt;br /&gt;
&lt;br /&gt;
The concept of identity is important because it makes explicit that reality has a definite nature. Since it exists in a particular way, it has characteristics. Since reality has an identity, it is knowable. &lt;br /&gt;
&lt;br /&gt;
Finally, it is important to separate the logical law of identity from the metaphysical law: the universe exists and has an identity, but this in itself is not the 'law of identity', for the logical law to exist, a mind must glean it, [[a priori]].&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Landauer, J. &amp;amp; Rowlands J., (2001)&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:28:53 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Identity</comments>		</item>
		<item>
			<title>The Law of Identity</title>
			<link>http://72.14.177.54/logic/The_Law_of_Identity</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Aristotle's Law of Identity   http://importanceofphilosophy.com/Graphics/Aristotle.gif&lt;br /&gt;
&lt;br /&gt;
For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
We can state this simply:&lt;br /&gt;
&lt;br /&gt;
A=A&lt;br /&gt;
&lt;br /&gt;
Or, in logical form:&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
Metaphysically, we can say that everything that exists has a specific nature. Each entity exists as something in particular and it has characteristics that are a part of what it is. &amp;quot;This leaf is red, solid, dry, rough, and flammable.&amp;quot; &amp;quot;This book is white, and has 312 pages.&amp;quot; &amp;quot;This coin is round, dense, smooth, and has a picture on it.&amp;quot; In all three of these cases we are referring to an entity with a specific identity; the particular type of identity, or the trait discussed, is not important. Their identities include all of their features, not just those mentioned.&lt;br /&gt;
&lt;br /&gt;
Identity is the concept that refers to this aspect of existence; the aspect of existing as something in particular, with specific characteristics. An entity without an identity cannot exist because it would be nothing. To exist is to exist as something, and that means to exist with a particular identity.&lt;br /&gt;
&lt;br /&gt;
To have an identity means to have a single identity; an object cannot have two identities. A tree cannot be a telephone, and a dog cannot be a cat. Each entity exists as something specific, its identity is particular, and it cannot exist as something else. An entity can have more than one characteristic, but any characteristic it has is a part of its identity. A car can be both blue and red, but not at the same time or not in the same respect. Whatever portion is blue cannot be red at the same time, in the same way. Half the car can be red, and the other half blue. But the whole car can't be both red and blue. These two traits, blue and red, each have single, particular identities.&lt;br /&gt;
&lt;br /&gt;
The concept of identity is important because it makes explicit that reality has a definite nature. Since it exists in a particular way, it has characteristics. Since reality has an identity, it is knowable. &lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;br /&gt;
* Landauer, J. &amp;amp; Rowlands J., (2001)&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:21:19 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Law_of_Identity</comments>		</item>
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			<title>The Laws of Classical Logic</title>
			<link>http://72.14.177.54/logic/The_Laws_of_Classical_Logic</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* The Axioms of Classical Logic */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Classical logic rests upon a foundation of axioms.  The axioms of classical logic, are a set of [[a priori]] abstractions that humans create, in order to make [[Classical Logic|categorical syllogisms]]; their existence is contingent upon sentient brains.   Some may argue, like myself, that these laws have correlates to [[basic laws of metaphysics]]&amp;lt;sup&amp;gt;1&amp;lt;/sup&amp;gt; and that this accounts for the 'utility' of logic, but it does not follow that logical rules are rules for the universe - they are rules for arguments.&lt;br /&gt;
&lt;br /&gt;
===The Axioms of Classical Logic===&lt;br /&gt;
&lt;br /&gt;
* [[The Law of Identity]]: Metaphysically, this law asserts that &amp;quot;A is A&amp;quot; or &amp;quot;anything is itself.&amp;quot; For propositions: &amp;quot;If a proposition is true, then it is true.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Excluded Middle]]: Metaphysically, this law asserts &amp;quot;anything is either A or not A.&amp;quot; For propositions: &amp;quot;A proposition, such as P, is either true or false.&amp;quot; We also refer to such statements as &amp;quot;tautologies&amp;quot;&lt;br /&gt;
&lt;br /&gt;
*[[The Law of Noncontradiction]]: Metaphysically, this law asserts:: &amp;quot;Nothing can be both A and not-A.&amp;quot; For propositions: &amp;quot;A proposition, P, can not be both true and false.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
All of our syllogisms rely on these laws - that any thing is equal to itself, that tautologies must be true, and that contradictions must be false. Classical logic holds that everything has a definite, non-contradictory nature. A [[metaphysical law of identity]] would hold that to be perceived or even exist at all it must have a definite, non-contradictory nature, but for our purposes, it is enough to say that If A, then A.&lt;br /&gt;
&lt;br /&gt;
==Self Evident Nature of Axioms==&lt;br /&gt;
&lt;br /&gt;
Seeing as axioms are the foundation to logic, it is not possible to use classical logic to justify them. However, Aristotle found this is unnecessary: the axioms of classical logic are held to be [[self evident]]. We hold that they are are [[self evident]] because all syllogisms rely on them, and because they can be defended through [[retortion]]. &lt;br /&gt;
&lt;br /&gt;
A defense through [[retortion]] occurs whenever an argument must rely opon the very principle it seeks to overturn. Any attempt to form a syllogism to refute the axioms of classical logic will have to rely on them ,leading to a self refutation (we call this type of self refutation the [[Stolen concept fallacy]].&lt;br /&gt;
&lt;br /&gt;
==Necessity and Contingency==&lt;br /&gt;
&lt;br /&gt;
An understanding of [[axiom]]s can be further advanced if the concepts of [[necessity]] and [[contingency]] are introduced. A [[proposition]] is said to be a [[necessary]] [[proposition]] if it's negation necessarily entails a contradiction. [[Axiom]]s are considered to be [[necessary]] [[proposition|propositions]].&lt;br /&gt;
&lt;br /&gt;
A [[proposition]] is said to be a [[contingent]] [[proposition]] if it can be either true or false. As we will learn later, [[Categorical Propositions]] are one type of statement that can be either true or false.&lt;br /&gt;
&lt;br /&gt;
==Controversy==&lt;br /&gt;
&lt;br /&gt;
While some logicians refer to these axioms as the &amp;quot;Three laws of thought&amp;quot;, implying that '''all''' cognition relies on them, it is important to realize that this presumption is false: not all logical systems rely on these axioms, and some logical systems do not rely on axioms at all. Other forms of logic, such as [[Propostional Logic]] instead rely on rules or definitions defined within the system, such as [[Well Formed Formular]].&lt;br /&gt;
&lt;br /&gt;
===What these axioms are NOT===&lt;br /&gt;
&lt;br /&gt;
It is also important to avoid conflating or confusing the so called &amp;quot;laws of thought&amp;quot; with set of nomological (Physical) laws for the universe. Logic is not cosmology. It is not descriptive of how the &lt;br /&gt;
universe works'. It is prescriptive: it sets forth a method of examining arguments.&lt;br /&gt;
&lt;br /&gt;
The universe is not 'logical', it merely '''is'''.&lt;br /&gt;
&lt;br /&gt;
It is also important not to confuse classical logic with psychology. The so called laws of thought are not rules for human behavior, they don't even cover all human thought: in our dreams, we are able to imagine contradictions, like being both the victim and the attacker, or being both young and old at the same time - human thought contains rational, irrational and non rational thought - both logic and emotions, impulses and instincts.&lt;br /&gt;
&lt;br /&gt;
Finally, there is no reason to hold that these axioms are &amp;quot;immaterial&amp;quot;, or transcendental. Such claims are usually based on arguments from ignorance. An incomplete physical account for abstractions is not a positive argument for an immaterial account for abstractions. Second, 'immateriality' is a negative concept, and a negative definition devoid of a universe of discourse, is meaningless. Unless someone can show how something immaterial can exist, how something immaterial can interact with physical brains, and how something immaterial can act - at all without violating basic physics (the principle of conservation of energy) then the claim that these logical laws that people create are transcendent or immaterial remains incoherent - because the term &amp;quot;immaterial&amp;quot; is meaningless.&lt;br /&gt;
&lt;br /&gt;
==For Advanced Students==&lt;br /&gt;
&lt;br /&gt;
The following section delves into the matter of axioms more deeply, and requires knowledge of symbolic logic. Those following the [[Course in Logic 101]] will learn everything required to grasp this section in later lessons, and can skip this section for now, if desired.&lt;br /&gt;
&lt;br /&gt;
As stated above, some logical systems to not require any axioms at all. For example, the set of axioms for the sentential, or propositional, logic is {} - the empty set!&lt;br /&gt;
&lt;br /&gt;
So how does such a system &amp;quot;get off the ground&amp;quot;?&lt;br /&gt;
&lt;br /&gt;
It creates a set of rules, defined within the system:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Let the set of English capital letters be well-formed formular (WFFs), which may be appended&lt;br /&gt;
by zero to an infinite amount of primes to indicate different WFFs&lt;br /&gt;
If A and B are WFFs, then (A v B) is a WFF&lt;br /&gt;
If A and B are WFFs, then (A &amp;amp; B) is a WFF&lt;br /&gt;
If A is a WFF, then (~A) is a WFF&lt;br /&gt;
If A and B are WFFs, then define (A -&amp;gt; B) to be ((~A) v B)&lt;br /&gt;
If A and B are WFFs, then define (A &amp;lt;-&amp;gt; B) to be ((A -&amp;gt; B) &amp;amp; (B -&amp;gt;A))&lt;br /&gt;
No other strings are WFFs&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
That defines our &amp;quot;grammar&amp;quot; for our fake little language that will turn into the propositional logic.&lt;br /&gt;
&lt;br /&gt;
Now define 21 rules of inference to allow us to move between WFFs:&lt;br /&gt;
&lt;br /&gt;
http://upload.wikimedia.org/wikipedia/commons/3/34/Propositional_Logic.png&lt;br /&gt;
&lt;br /&gt;
Then we define a function that maps each propositional variable to two values: &amp;quot;True&amp;quot; or &amp;quot;false&amp;quot; (or 1 and 0, or &amp;quot;your mom&amp;quot; and &amp;quot;your dad&amp;quot; - it doesn't matter from a formal point of view).&lt;br /&gt;
&lt;br /&gt;
Then come the soundness (if you can derive a string from a set of strings above, then it must be &amp;quot;true&amp;quot;) and completeness (all &amp;quot;true&amp;quot; strings can be derived from the rules above) proofs, and we're done! The system is both sound and complete.&lt;br /&gt;
&lt;br /&gt;
All this in much more detail can be found at:&lt;br /&gt;
&lt;br /&gt;
http://www.algebra.com/algebra/about/history/Propositional-logic.wikipedia#Axioms&lt;br /&gt;
&lt;br /&gt;
The point is that there can be no axioms in this logic, the most basic of all modern logics (there are other formulations that do have axioms, though): everything is definitional. And how does one argue with a definition? My point is: the answer to the question &amp;quot;why doesn't everyone accept the axioms of logic?&amp;quot; is that it can be the case that there's nothing to accept. Literally.&lt;br /&gt;
&lt;br /&gt;
This system even allows us to create a proof for the law of non contradiction:&lt;br /&gt;
&amp;lt;pre&amp;gt;&lt;br /&gt;
Proof (by reductio):&lt;br /&gt;
&lt;br /&gt;
1) (A &amp;amp; ~A) [Proposition]&lt;br /&gt;
2) A [Conjunction elimination from 1]&lt;br /&gt;
3) ~A [Conjunction elimination from 1]&lt;br /&gt;
4) ~(A &amp;amp; ~A) [Reductio, 1 - 3]&lt;br /&gt;
&lt;br /&gt;
QED&lt;br /&gt;
&amp;lt;/pre&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This is a proof of the [[law of noncontradiction]] (LNC) using the simplest logical system there is, which is called sentential, or [[propositional]] logic. The rules used in the proof were cited in square brackets. The LNC is line 4 of the proof. In short, the argument shows that the LNC is derivable from logic in the most rigorous way possible: a deductive proof.&lt;br /&gt;
&lt;br /&gt;
This said, there are cases where certain logics don't &amp;quot;work&amp;quot; (for example, &amp;quot;all men are mortal, Socrates is a man, therefore Socrates is mortal&amp;quot; is an invalid argument under the logic given above. I'll leave it as an exercise for the interested to figure out why)&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt;.  &lt;br /&gt;
&lt;br /&gt;
Those taking the [[Course in Logic 101]] will want to proceed to the next section: &lt;br /&gt;
[[The Difference Between Believing and Knowing]]&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
====Footnotes====&lt;br /&gt;
&lt;br /&gt;
1. Metaphysics is a term also invented by [[Aristotle]]; and it has to do with theories concerning how existence itself 'works'.  &lt;br /&gt;
&lt;br /&gt;
2. Ok, here's the answer:   http://en.wikipedia.org/wiki/First-order_logic&lt;br /&gt;
&lt;br /&gt;
Propositional logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal * Socrates is a man * Therefore, Socrates is mortal &lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A * B * therefore C &lt;br /&gt;
&lt;br /&gt;
which is invalid, as there is no connection between the premises and the conclusion. &lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), &amp;quot;Introduction to Logic&amp;quot;, 11th Edition.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:16:54 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:The_Laws_of_Classical_Logic</comments>		</item>
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			<title>Main Page</title>
			<link>http://72.14.177.54/logic/Main_Page</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* References */&lt;/p&gt;
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&lt;div&gt;==Introduction==&lt;br /&gt;
&lt;br /&gt;
This site is intended as a resource for those interested in learning Logic. While the author of this page will take a scholarly approach to the subject, this page will approach the subject in a more user friendly manner than available at Wikipedia, at times even using colloquial language. The site will offer a full [[Course in Logic 101]], based on two of the most reliable texts on logic: Copi and Cohen's ''Introduction to Logic (11th Edition)'' and Hurely's ''A Concise Introduction to Logic (7th Edition)''. The [[Course in Logic 101|course]] will cover the basics of Logic, [[Classical Logic]], [[Propositional Logic]], [[Predicate Logic]], [[Modal Logic]] and [[Inductive Logic]] including a discussion of [[Inductive Logic|Bayesian Theory]]. Those interested in taking the [[Course in Logic 101|course]] can consult that page for the proper order of reading the pages of this site.&lt;br /&gt;
&lt;br /&gt;
Now, let's begin.&lt;br /&gt;
&lt;br /&gt;
'''Logic''', (from the Greek word &amp;amp;lambda;&amp;amp;#972;&amp;amp;gamma;&amp;amp;omicron;&amp;amp;sigmaf; (''logos''), originally meaning ''the word'', but also referring to ''speech'' or ''reason'') is the science of evaluating the reasoning within [[Argument|arguments]].&lt;br /&gt;
&lt;br /&gt;
==Nature of logic==  &lt;br /&gt;
&lt;br /&gt;
Logic arose from a concern with correctness of [[argument]]ation (See [[Aristotle]]).  Logic is generally accepted and understood by logicians as a set of rules that tell us when an [[argument|argument's]] premises support their conclusion. Logic specifically deals with inferences whose validity can be traced back to the formal features of the representations that are involved in that inference.'' (Hofweber 2004).  &lt;br /&gt;
&lt;br /&gt;
Therefore, a further understanding of just what logic is, can be enhanced by delineating it from what it is not:&lt;br /&gt;
&lt;br /&gt;
*Logic is not the 'groundness of being' - that's metaphysics.&lt;br /&gt;
*Logic is not a set of laws that governs the universe - that's physics. &lt;br /&gt;
*Logic is not an immaterial &amp;quot;entity&amp;quot; that transcends reality - that's speculative theology.&lt;br /&gt;
*Logic is no a method for 'studying the world' -  that's science. &lt;br /&gt;
*Logic is not the method for assessing axioms - that's a matter of pure reason. &lt;br /&gt;
*Logic is not a way of evaluating 'truth' - that's philosophy. &lt;br /&gt;
*Logic is not a set of laws that governs human behavior - that's psychology. &lt;br /&gt;
*Logic is not even a study of how people reason - [[Non Logical Modes of Thought|Fortunately]] there is more to human reason than just logic.&lt;br /&gt;
&lt;br /&gt;
[[Immanuel Kant]] introduced an alternative idea as to what logic is.  He argued that logic should be conceived as the science of judgment, an idea taken up by [[Gottlob Frege]]. However, modern psychologists have demonstrated that a significant percentage of human judgment is clearly non logical.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Relation to other sciences===&lt;br /&gt;
&lt;br /&gt;
Closely related to logic is semantics, or the philosophy of language, which concerns the meaning of the words and sentences; epistemology, or the theory of knowledge, which concerns the conditions under which assertions are true; and the psychology of reasoning, which concerns the mental processes involved in reasoning.  Logic, however, is generally understood to describe reasoning in a prescriptive manner (i.e.  it describes how reasoning ought to take place), whereas psychology is descriptive and therefore more inclusive vis-a-vis the various methods of judgment humans actually use.  &lt;br /&gt;
&lt;br /&gt;
===Definition of an Argument===&lt;br /&gt;
&lt;br /&gt;
An [[argument]] is made up of a group  of statements we call [[proposition]]s. We use the term [[proposition]] instead of [[sentence]] because a proposition is more than just a sentence, it is a declarative sentence that contains a [[truth value]]. In the case of [[Classical Logic]], which is based on the [[Law of the Excluded Middle]], this truth value must  either be &amp;quot;true&amp;quot; or false&amp;quot; . &lt;br /&gt;
&lt;br /&gt;
There are two types of [[proposition]]s. The first, the [[Premises|Premise]], makes a commitment to truth, and is used as evidence to support the second type of proposition, the [[Conclusion]], which is the claim the arguer wants to prove. An argument must at least imply one of each. The study of logic, therefore, is the effort to determine the conditions under which one is justified in passing from the premises to the conclusion that logically must follow them.&lt;br /&gt;
&lt;br /&gt;
=== Examining Arguments: Informal, formal, and symbolic logic===&lt;br /&gt;
&lt;br /&gt;
Arguments can be examined through examining their premises, the form of the argument, and by looking at them abstractly. We use the terms &amp;quot;informal&amp;quot;, &amp;quot;formal&amp;quot; and &amp;quot;symbolic&amp;quot; to capture these meanings.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Informal Logic]]''' is the study of natural language [[Argument|arguments]].  The study of fallacies is an especially important branch of informal logic.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Formal Logic]]''' is the study of inference with purely formal content, where that content is made explicit. (An inference possesses a purely formal content if it can be expressed as a particular application of a wholly abstract rule, that is, a rule that is not about any particular thing or property.  We will see later that on many definitions of logic, logical inference and inference with purely formal content are the same thing.  This does not render the notion of informal logic vacuous, since one may wish to investigate logic without committing to a ''particular'' formal analysis.)&lt;br /&gt;
* '''[[Propositional Logic|Symbolic Logic]]''' is closely related to formal logic: it the study of symbolic abstractions that capture the formal features of logical inference.&lt;br /&gt;
&lt;br /&gt;
===Consistency, soundness, and completeness===&lt;br /&gt;
&lt;br /&gt;
There are three valuable properties that formal systems can have:&lt;br /&gt;
&lt;br /&gt;
:* '''[[Consistency]]''', which means that none of the theorems of the system contradict each other.&lt;br /&gt;
&lt;br /&gt;
:* '''[[Validity, Strength, Soundness and Cogency|Soundness]]''', which means that the system's rules of derivation will never let you infer anything false, so long as you start with only true premises.  So if a system is sound (and its axioms, if any, are true), then the theorems of a sound formal system are the [[truth]]s.  All of the theorems of a system that has no axioms are its truths and sometimes the truths of such a system are called 'logical truths.' (Note that if a system is not consistent, it cannot be sound. This is because a contradiction is always false, so if two theorems contradict at least one is false.)&lt;br /&gt;
&lt;br /&gt;
:* '''[[Completeness]]''', which means that there are no true sentences in the system that cannot, at least in principle, be proved using the derivation rules (and axioms, if any) of the system. &lt;br /&gt;
&lt;br /&gt;
Not all systems achieve all three virtues. It has been proven by [[Kurt Gödel]] that a system with enough axioms and/or rules of derivation to derive the principles of arithmetic cannot be both consistent and complete. This is called [[Gödel's Incompleteness Theorem]].&lt;br /&gt;
&lt;br /&gt;
===Deductive and inductive reasoning===&lt;br /&gt;
&lt;br /&gt;
Originally, logic consisted only of [[Deductive and Inductive Logic|deductive reasoning]] which concerns what follows universally from given premises.  However, it is important to note that [[Deductive and Inductive Logic|inductive reasoning]]&amp;amp;mdash;the study of deriving a reliable generalization from observations&amp;amp;mdash;has sometimes been included in the study of logic. Correspondingly, we must distinguish between deductive validity and inductive validity.  An inference is deductively valid if and only if there is no possible situation in which all the premises are true and the conclusion false.  The notion of deductive validity can be rigorously stated for systems of [[Formal and Informal Logic|formal logic]] in terms of the well-understood notions of [[semantics]].  Inductive validity on the other hand requires us to define a ''reliable generalization'' of some set of observations. The task of providing this definition may be approached  in various ways, some less formal than others; some of these definitions may use [[mathematical model]]s of probability.  For the most part this discussion of logic deals only with deductive logic.&lt;br /&gt;
&lt;br /&gt;
==Types of logic==&lt;br /&gt;
&lt;br /&gt;
Formal logic encompasses a wide variety of logical systems.  Various systems of logic include [[Classical Logic|Classical]] or [[Classical Logic|Syllogistic logic]], [[Predicate Logic]], [[Propositional Logic]], and [[Modal Logic]], and formal systems are indispensable in all branches of [[mathematical logic]].  &lt;br /&gt;
&lt;br /&gt;
===Syllogistic or Classical Logic===&lt;br /&gt;
&lt;br /&gt;
The ''Organon'' was [[Aristotle]]'s body of work on logic, with the ''Prior Analytics'' constituting the first explicit work in [[Formal and Informal Logic|formal logic]], introducing to the world the [[Syllogism|syllogism]]. [[Classical Logic|Syllogistic Logic]], [[Classical Logic|Term logic]], [[Classical Logic|Aristotelean Logic]] or [[Classical Logic]] are all references to the logical form of the [[Syllogism|syllogism]]. Syllogistic logic is the analysis of the judgments into propositions consisting of two terms that are related by one of a fixed number of relations, and the expression of inferences by means of [[syllogism]]s that consisted of two propositions sharing a common term as premise, and a conclusion which was a proposition involving the two unrelated terms from the premises.&lt;br /&gt;
&lt;br /&gt;
Aristotle's work was regarded in classical times and from medieval times in Europe and the Middle East as the very picture of a fully worked out system.  It was not alone: the [[Stoics]] proposed a system of [[Propositional Logic]] that was studied by medieval logicians; nor was the perfection of Aristotle's system undisputed; for example the [[problem of multiple generality]] was recognized in medieval times.  Nonetheless, problems with syllogistic logic were not seen as being in need of revolutionary solutions.&lt;br /&gt;
&lt;br /&gt;
Today, some academics claim that Aristotle's system is generally seen as having little more than historical value (though there is some current interest in extending term logics), regarded as made obsolete by the advent of [[Sentential Logic]] and the [[Predicate Logic|predicate calculus]].&lt;br /&gt;
&lt;br /&gt;
===Propositional Logic===&lt;br /&gt;
 &lt;br /&gt;
Logic as it is studied today is a very different subject from [[Classical Logic]];  the principal difference is the innovation of [[Propositional Logic]] and [[Predicate Logic]]. Propositional Logic allows for more complex argument forms than classical syllogisms. In propositional logic, propositions are represented by ''symbols'' and ''connectors'', so that the statement's logical form can be assessed for cases of truth and falsity, which in turn allows us to assess the entire argument's form for validity or invalidity. In symbolic, or propositional logic, a simple statement, containing one proposition, is is referred to as an ''atomic statement'', and is symbolized by one letter, such as p. A compound statement, with more than one proposition holding some relationship to another proposition, is referred to as a molecular statement, which may be symbolized as p v q. The v symbol just used is a connective: Atomic propositions become molecular propositions when they are joined by connectives. &lt;br /&gt;
&lt;br /&gt;
===Predicate Logic===&lt;br /&gt;
&lt;br /&gt;
However, just as limits in Classical Logical led to [[Propositional Logic]], limits in Propositional Logic pointed to the need for a new logic. Propositional Logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument:&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal&lt;br /&gt;
    * Socrates is a man&lt;br /&gt;
    * Therefore, Socrates is mortal&lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A&lt;br /&gt;
    * B&lt;br /&gt;
    * ∴ C (∴ means &amp;quot;therefore&amp;quot;&lt;br /&gt;
&lt;br /&gt;
which is invalid, because there are no connectors between the premises and between the premises and the conclusion.&lt;br /&gt;
&lt;br /&gt;
Therefore, the need for a ''First Order'', or [[Predicate Logic]] became apparent. The new ingredient of first-order logic not found in propositional logic is [[Predicate Logic|quantification]]: where φ is any (well-formed) formula, the new constructions ∀x φ and ∃x φ — read &amp;quot;for all x, φ&amp;quot; and &amp;quot;for some x, φ&amp;quot; — are introduced, where x is an individual variable whose range is the set of individuals of some given universe of discourse (or domain). For example, if the universe consists solely of people, then x ranges over people. For convenience, we write φ as φ(x) to show that it contains only the variable x free and, for b a member of the universe, we let φ[b] express that b satisfies (i.e. has the property expressed by) φ. Then ∀x φ(x) states that φ[b] is true for every b in the universe, and ∃x φ(x) means that there is a b (in the universe) such that φ[b] holds.&lt;br /&gt;
&lt;br /&gt;
The argument about Socrates can be formalized in first-order logic as follows. Let the universe of discourse be the set of all people, living and deceased, and let Man(x) be a predicate (which, informally, means that the person represented by variable x is a man) and Mortal(x) be a second predicate. Then the argument above becomes&lt;br /&gt;
&lt;br /&gt;
    * ∀ x (Man(x) → Mortal(x))&lt;br /&gt;
    * Man(Socrates)&lt;br /&gt;
    * ∴ Mortal(Socrates)&lt;br /&gt;
&lt;br /&gt;
A literal translation of the first line would be &amp;quot;For all x, if x is described by 'Man', x must also be described by 'Mortal'.&amp;quot; The second line states that the predicate &amp;quot;Man&amp;quot; applies to Socrates, and the third line translates to &amp;quot;Therefore, the description 'Mortal' applies to Socrates.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Modal logic===&lt;br /&gt;
&lt;br /&gt;
In language, [[modality]] deals with the phenomenon that subparts of a sentence may have their semantics modified by special verbs or modal particles.  For example, &amp;quot;''We go to the games''&amp;quot; can be modified to give &amp;quot;''We should go to the games''&amp;quot;, and &amp;quot;''We can go to the games''&amp;quot;&amp;quot; and perhaps &amp;quot;''We will go to the games''&amp;quot;.  More abstractly, we might say that modality affects the circumstances in which we take an assertion to be satisfied.&lt;br /&gt;
&lt;br /&gt;
The logical study of modality dates back to [[Aristotle]], who was concerned with the [[alethic modalities]] of necessity and possibility, which he observed to be dual in the sense of [[De Morgan duality]].  While the study of necessity and possibility remained important to philosophers, little logical innovation happened until the landmark investigations of [[Clarence Irving Lewis]] in [[1918]], who formulated a family of rival axiomatisations of the alethic modalities.  His work unleashed a torrent of new work on the topic, expanding the kinds of modality treated to include [[deontic logic]] and [[epistemic logic]].  The seminal work of [[Arthur Prior]] applied the same formal language to treat [[temporal logic]] and paved the way for the marriage of the two subjects.  [[Saul Kripke]] discovered (contemporaneously with rivals) his theory of [[frame semantics]] which revolutionized the formal technology available to modal logicians and gave a new [[graph theory|graph-theoretic]] way of looking at modality that has driven many applications in [[computational linguistics]] and [[computer science]], such as [[dynamic logic]].&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
Students following the [[Course in Logic 101]] should proceed to the section entitled: [[The Laws of Classical Logic]]&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
 &lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), ''Introduction to Logic'', 11th Edition.&lt;br /&gt;
&lt;br /&gt;
* Gabbay, D.M., and Guenthner, F. (eds., 2001-2005), ''Handbook of Philosophical Logic'', 13 vols., 2nd edition, Kluwer Publishers, Dordrecht.&lt;br /&gt;
&lt;br /&gt;
* Hilbert, D., and Ackermann, W. (1928), ''Grundzüge der theoretischen Logik'' (''Principles of Theoretical Logic''), Springer-Verlag.&lt;br /&gt;
&lt;br /&gt;
* Hodges, W. (2001), ''Logic.  An introduction to Elementary Logic'', Penguin Books.&lt;br /&gt;
&lt;br /&gt;
* Hofweber, T. (2004), &amp;quot;Logic and Ontology&amp;quot;, ''Stanford Encyclopedia of Philosophy'', Edward N. Zalta (ed.), [http://plato.stanford.edu/entries/logic-ontology/ Eprint].&lt;br /&gt;
&lt;br /&gt;
* Hughes, R.I.G. (ed., 1993), ''A Philosophical Companion to First-Order Logic'', Hackett Publishing.&lt;br /&gt;
&lt;br /&gt;
* Hurely, P. J.  (2000) ''A Concise Introduction to Logic'' - 7th Edition&lt;br /&gt;
&lt;br /&gt;
* Kneale, W., and Kneale, M., (1962), ''The Development of Logic'', Oxford University Press, London, UK.&lt;br /&gt;
&lt;br /&gt;
* Priest, G. (2004), &amp;quot;Dialetheism&amp;quot;, ''Stanford Encyclopedia of Philosophy'', Edward N. Zalta (ed.), [http://plato.stanford.edu/entries/dialetheism Eprint].&lt;br /&gt;
&lt;br /&gt;
==See also== &lt;br /&gt;
* [[Course in Logic 101]] This takes the interested reader to every major page of the site.&lt;br /&gt;
* [[The Laws of Classical Logic]]  This page presents the axioms of classical logic&lt;br /&gt;
* [[Validity, Strength, Soundness and Cogency ]]&lt;br /&gt;
* [[Deductive and Inductive Logic]]&lt;br /&gt;
* [[Fallacies|Logical Fallacies]]&lt;br /&gt;
* [[Informal Fallacies]]  This page presents a list of informal fallacies found in arguments.&lt;br /&gt;
* [[Formal Fallacies]]&lt;br /&gt;
* [[Valid and Invalid Logical Forms]]&lt;br /&gt;
* [[Categorical Propositions]] &lt;br /&gt;
* [[Classical Logic]]&lt;br /&gt;
* [[Propositional Logic]] &lt;br /&gt;
* [[Predicate Logic]]&lt;br /&gt;
* [[Inductive Logic]] &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
[[Category:Logic]]&lt;br /&gt;
[[Category:Tutorials]]&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:14:15 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Main_Page</comments>		</item>
		<item>
			<title>Main Page</title>
			<link>http://72.14.177.54/logic/Main_Page</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* References */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;==Introduction==&lt;br /&gt;
&lt;br /&gt;
This site is intended as a resource for those interested in learning Logic. While the author of this page will take a scholarly approach to the subject, this page will approach the subject in a more user friendly manner than available at Wikipedia, at times even using colloquial language. The site will offer a full [[Course in Logic 101]], based on two of the most reliable texts on logic: Copi and Cohen's ''Introduction to Logic (11th Edition)'' and Hurely's ''A Concise Introduction to Logic (7th Edition)''. The [[Course in Logic 101|course]] will cover the basics of Logic, [[Classical Logic]], [[Propositional Logic]], [[Predicate Logic]], [[Modal Logic]] and [[Inductive Logic]] including a discussion of [[Inductive Logic|Bayesian Theory]]. Those interested in taking the [[Course in Logic 101|course]] can consult that page for the proper order of reading the pages of this site.&lt;br /&gt;
&lt;br /&gt;
Now, let's begin.&lt;br /&gt;
&lt;br /&gt;
'''Logic''', (from the Greek word &amp;amp;lambda;&amp;amp;#972;&amp;amp;gamma;&amp;amp;omicron;&amp;amp;sigmaf; (''logos''), originally meaning ''the word'', but also referring to ''speech'' or ''reason'') is the science of evaluating the reasoning within [[Argument|arguments]].&lt;br /&gt;
&lt;br /&gt;
==Nature of logic==  &lt;br /&gt;
&lt;br /&gt;
Logic arose from a concern with correctness of [[argument]]ation (See [[Aristotle]]).  Logic is generally accepted and understood by logicians as a set of rules that tell us when an [[argument|argument's]] premises support their conclusion. Logic specifically deals with inferences whose validity can be traced back to the formal features of the representations that are involved in that inference.'' (Hofweber 2004).  &lt;br /&gt;
&lt;br /&gt;
Therefore, a further understanding of just what logic is, can be enhanced by delineating it from what it is not:&lt;br /&gt;
&lt;br /&gt;
*Logic is not the 'groundness of being' - that's metaphysics.&lt;br /&gt;
*Logic is not a set of laws that governs the universe - that's physics. &lt;br /&gt;
*Logic is not an immaterial &amp;quot;entity&amp;quot; that transcends reality - that's speculative theology.&lt;br /&gt;
*Logic is no a method for 'studying the world' -  that's science. &lt;br /&gt;
*Logic is not the method for assessing axioms - that's a matter of pure reason. &lt;br /&gt;
*Logic is not a way of evaluating 'truth' - that's philosophy. &lt;br /&gt;
*Logic is not a set of laws that governs human behavior - that's psychology. &lt;br /&gt;
*Logic is not even a study of how people reason - [[Non Logical Modes of Thought|Fortunately]] there is more to human reason than just logic.&lt;br /&gt;
&lt;br /&gt;
[[Immanuel Kant]] introduced an alternative idea as to what logic is.  He argued that logic should be conceived as the science of judgment, an idea taken up by [[Gottlob Frege]]. However, modern psychologists have demonstrated that a significant percentage of human judgment is clearly non logical.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Relation to other sciences===&lt;br /&gt;
&lt;br /&gt;
Closely related to logic is semantics, or the philosophy of language, which concerns the meaning of the words and sentences; epistemology, or the theory of knowledge, which concerns the conditions under which assertions are true; and the psychology of reasoning, which concerns the mental processes involved in reasoning.  Logic, however, is generally understood to describe reasoning in a prescriptive manner (i.e.  it describes how reasoning ought to take place), whereas psychology is descriptive and therefore more inclusive vis-a-vis the various methods of judgment humans actually use.  &lt;br /&gt;
&lt;br /&gt;
===Definition of an Argument===&lt;br /&gt;
&lt;br /&gt;
An [[argument]] is made up of a group  of statements we call [[proposition]]s. We use the term [[proposition]] instead of [[sentence]] because a proposition is more than just a sentence, it is a declarative sentence that contains a [[truth value]]. In the case of [[Classical Logic]], which is based on the [[Law of the Excluded Middle]], this truth value must  either be &amp;quot;true&amp;quot; or false&amp;quot; . &lt;br /&gt;
&lt;br /&gt;
There are two types of [[proposition]]s. The first, the [[Premises|Premise]], makes a commitment to truth, and is used as evidence to support the second type of proposition, the [[Conclusion]], which is the claim the arguer wants to prove. An argument must at least imply one of each. The study of logic, therefore, is the effort to determine the conditions under which one is justified in passing from the premises to the conclusion that logically must follow them.&lt;br /&gt;
&lt;br /&gt;
=== Examining Arguments: Informal, formal, and symbolic logic===&lt;br /&gt;
&lt;br /&gt;
Arguments can be examined through examining their premises, the form of the argument, and by looking at them abstractly. We use the terms &amp;quot;informal&amp;quot;, &amp;quot;formal&amp;quot; and &amp;quot;symbolic&amp;quot; to capture these meanings.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Informal Logic]]''' is the study of natural language [[Argument|arguments]].  The study of fallacies is an especially important branch of informal logic.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Formal Logic]]''' is the study of inference with purely formal content, where that content is made explicit. (An inference possesses a purely formal content if it can be expressed as a particular application of a wholly abstract rule, that is, a rule that is not about any particular thing or property.  We will see later that on many definitions of logic, logical inference and inference with purely formal content are the same thing.  This does not render the notion of informal logic vacuous, since one may wish to investigate logic without committing to a ''particular'' formal analysis.)&lt;br /&gt;
* '''[[Propositional Logic|Symbolic Logic]]''' is closely related to formal logic: it the study of symbolic abstractions that capture the formal features of logical inference.&lt;br /&gt;
&lt;br /&gt;
===Consistency, soundness, and completeness===&lt;br /&gt;
&lt;br /&gt;
There are three valuable properties that formal systems can have:&lt;br /&gt;
&lt;br /&gt;
:* '''[[Consistency]]''', which means that none of the theorems of the system contradict each other.&lt;br /&gt;
&lt;br /&gt;
:* '''[[Validity, Strength, Soundness and Cogency|Soundness]]''', which means that the system's rules of derivation will never let you infer anything false, so long as you start with only true premises.  So if a system is sound (and its axioms, if any, are true), then the theorems of a sound formal system are the [[truth]]s.  All of the theorems of a system that has no axioms are its truths and sometimes the truths of such a system are called 'logical truths.' (Note that if a system is not consistent, it cannot be sound. This is because a contradiction is always false, so if two theorems contradict at least one is false.)&lt;br /&gt;
&lt;br /&gt;
:* '''[[Completeness]]''', which means that there are no true sentences in the system that cannot, at least in principle, be proved using the derivation rules (and axioms, if any) of the system. &lt;br /&gt;
&lt;br /&gt;
Not all systems achieve all three virtues. It has been proven by [[Kurt Gödel]] that a system with enough axioms and/or rules of derivation to derive the principles of arithmetic cannot be both consistent and complete. This is called [[Gödel's Incompleteness Theorem]].&lt;br /&gt;
&lt;br /&gt;
===Deductive and inductive reasoning===&lt;br /&gt;
&lt;br /&gt;
Originally, logic consisted only of [[Deductive and Inductive Logic|deductive reasoning]] which concerns what follows universally from given premises.  However, it is important to note that [[Deductive and Inductive Logic|inductive reasoning]]&amp;amp;mdash;the study of deriving a reliable generalization from observations&amp;amp;mdash;has sometimes been included in the study of logic. Correspondingly, we must distinguish between deductive validity and inductive validity.  An inference is deductively valid if and only if there is no possible situation in which all the premises are true and the conclusion false.  The notion of deductive validity can be rigorously stated for systems of [[Formal and Informal Logic|formal logic]] in terms of the well-understood notions of [[semantics]].  Inductive validity on the other hand requires us to define a ''reliable generalization'' of some set of observations. The task of providing this definition may be approached  in various ways, some less formal than others; some of these definitions may use [[mathematical model]]s of probability.  For the most part this discussion of logic deals only with deductive logic.&lt;br /&gt;
&lt;br /&gt;
==Types of logic==&lt;br /&gt;
&lt;br /&gt;
Formal logic encompasses a wide variety of logical systems.  Various systems of logic include [[Classical Logic|Classical]] or [[Classical Logic|Syllogistic logic]], [[Predicate Logic]], [[Propositional Logic]], and [[Modal Logic]], and formal systems are indispensable in all branches of [[mathematical logic]].  &lt;br /&gt;
&lt;br /&gt;
===Syllogistic or Classical Logic===&lt;br /&gt;
&lt;br /&gt;
The ''Organon'' was [[Aristotle]]'s body of work on logic, with the ''Prior Analytics'' constituting the first explicit work in [[Formal and Informal Logic|formal logic]], introducing to the world the [[Syllogism|syllogism]]. [[Classical Logic|Syllogistic Logic]], [[Classical Logic|Term logic]], [[Classical Logic|Aristotelean Logic]] or [[Classical Logic]] are all references to the logical form of the [[Syllogism|syllogism]]. Syllogistic logic is the analysis of the judgments into propositions consisting of two terms that are related by one of a fixed number of relations, and the expression of inferences by means of [[syllogism]]s that consisted of two propositions sharing a common term as premise, and a conclusion which was a proposition involving the two unrelated terms from the premises.&lt;br /&gt;
&lt;br /&gt;
Aristotle's work was regarded in classical times and from medieval times in Europe and the Middle East as the very picture of a fully worked out system.  It was not alone: the [[Stoics]] proposed a system of [[Propositional Logic]] that was studied by medieval logicians; nor was the perfection of Aristotle's system undisputed; for example the [[problem of multiple generality]] was recognized in medieval times.  Nonetheless, problems with syllogistic logic were not seen as being in need of revolutionary solutions.&lt;br /&gt;
&lt;br /&gt;
Today, some academics claim that Aristotle's system is generally seen as having little more than historical value (though there is some current interest in extending term logics), regarded as made obsolete by the advent of [[Sentential Logic]] and the [[Predicate Logic|predicate calculus]].&lt;br /&gt;
&lt;br /&gt;
===Propositional Logic===&lt;br /&gt;
 &lt;br /&gt;
Logic as it is studied today is a very different subject from [[Classical Logic]];  the principal difference is the innovation of [[Propositional Logic]] and [[Predicate Logic]]. Propositional Logic allows for more complex argument forms than classical syllogisms. In propositional logic, propositions are represented by ''symbols'' and ''connectors'', so that the statement's logical form can be assessed for cases of truth and falsity, which in turn allows us to assess the entire argument's form for validity or invalidity. In symbolic, or propositional logic, a simple statement, containing one proposition, is is referred to as an ''atomic statement'', and is symbolized by one letter, such as p. A compound statement, with more than one proposition holding some relationship to another proposition, is referred to as a molecular statement, which may be symbolized as p v q. The v symbol just used is a connective: Atomic propositions become molecular propositions when they are joined by connectives. &lt;br /&gt;
&lt;br /&gt;
===Predicate Logic===&lt;br /&gt;
&lt;br /&gt;
However, just as limits in Classical Logical led to [[Propositional Logic]], limits in Propositional Logic pointed to the need for a new logic. Propositional Logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument:&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal&lt;br /&gt;
    * Socrates is a man&lt;br /&gt;
    * Therefore, Socrates is mortal&lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A&lt;br /&gt;
    * B&lt;br /&gt;
    * ∴ C (∴ means &amp;quot;therefore&amp;quot;&lt;br /&gt;
&lt;br /&gt;
which is invalid, because there are no connectors between the premises and between the premises and the conclusion.&lt;br /&gt;
&lt;br /&gt;
Therefore, the need for a ''First Order'', or [[Predicate Logic]] became apparent. The new ingredient of first-order logic not found in propositional logic is [[Predicate Logic|quantification]]: where φ is any (well-formed) formula, the new constructions ∀x φ and ∃x φ — read &amp;quot;for all x, φ&amp;quot; and &amp;quot;for some x, φ&amp;quot; — are introduced, where x is an individual variable whose range is the set of individuals of some given universe of discourse (or domain). For example, if the universe consists solely of people, then x ranges over people. For convenience, we write φ as φ(x) to show that it contains only the variable x free and, for b a member of the universe, we let φ[b] express that b satisfies (i.e. has the property expressed by) φ. Then ∀x φ(x) states that φ[b] is true for every b in the universe, and ∃x φ(x) means that there is a b (in the universe) such that φ[b] holds.&lt;br /&gt;
&lt;br /&gt;
The argument about Socrates can be formalized in first-order logic as follows. Let the universe of discourse be the set of all people, living and deceased, and let Man(x) be a predicate (which, informally, means that the person represented by variable x is a man) and Mortal(x) be a second predicate. Then the argument above becomes&lt;br /&gt;
&lt;br /&gt;
    * ∀ x (Man(x) → Mortal(x))&lt;br /&gt;
    * Man(Socrates)&lt;br /&gt;
    * ∴ Mortal(Socrates)&lt;br /&gt;
&lt;br /&gt;
A literal translation of the first line would be &amp;quot;For all x, if x is described by 'Man', x must also be described by 'Mortal'.&amp;quot; The second line states that the predicate &amp;quot;Man&amp;quot; applies to Socrates, and the third line translates to &amp;quot;Therefore, the description 'Mortal' applies to Socrates.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Modal logic===&lt;br /&gt;
&lt;br /&gt;
In language, [[modality]] deals with the phenomenon that subparts of a sentence may have their semantics modified by special verbs or modal particles.  For example, &amp;quot;''We go to the games''&amp;quot; can be modified to give &amp;quot;''We should go to the games''&amp;quot;, and &amp;quot;''We can go to the games''&amp;quot;&amp;quot; and perhaps &amp;quot;''We will go to the games''&amp;quot;.  More abstractly, we might say that modality affects the circumstances in which we take an assertion to be satisfied.&lt;br /&gt;
&lt;br /&gt;
The logical study of modality dates back to [[Aristotle]], who was concerned with the [[alethic modalities]] of necessity and possibility, which he observed to be dual in the sense of [[De Morgan duality]].  While the study of necessity and possibility remained important to philosophers, little logical innovation happened until the landmark investigations of [[Clarence Irving Lewis]] in [[1918]], who formulated a family of rival axiomatisations of the alethic modalities.  His work unleashed a torrent of new work on the topic, expanding the kinds of modality treated to include [[deontic logic]] and [[epistemic logic]].  The seminal work of [[Arthur Prior]] applied the same formal language to treat [[temporal logic]] and paved the way for the marriage of the two subjects.  [[Saul Kripke]] discovered (contemporaneously with rivals) his theory of [[frame semantics]] which revolutionized the formal technology available to modal logicians and gave a new [[graph theory|graph-theoretic]] way of looking at modality that has driven many applications in [[computational linguistics]] and [[computer science]], such as [[dynamic logic]].&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
Students following the [[Course in Logic 101]] should proceed to the section entitled: [[The Laws of Classical Logic]]&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
 &lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), ''Introduction to Logic'', 11th Edition.&lt;br /&gt;
&lt;br /&gt;
* Gabbay, D.M., and Guenthner, F. (eds., 2001-2005), ''Handbook of Philosophical Logic'', 13 vols., 2nd edition, Kluwer Publishers, Dordrecht.&lt;br /&gt;
&lt;br /&gt;
* Hilbert, D., and Ackermann, W. (1928), ''Grundzüge der theoretischen Logik'' (''[[Principles of Theoretical Logic]]''), Springer-Verlag.&lt;br /&gt;
&lt;br /&gt;
* Hodges, W. (2001), ''Logic.  An introduction to Elementary Logic'', Penguin Books.&lt;br /&gt;
&lt;br /&gt;
* Hofweber, T. (2004), &amp;quot;Logic and Ontology&amp;quot;, ''[[Stanford Encyclopedia of Philosophy]]'', [[Edward N. Zalta]] (ed.), [http://plato.stanford.edu/entries/logic-ontology/ Eprint].&lt;br /&gt;
&lt;br /&gt;
* Hughes, R.I.G. (ed., 1993), ''A Philosophical Companion to First-Order Logic'', Hackett Publishing.&lt;br /&gt;
&lt;br /&gt;
* Hurely, P. J.  (2000) ''A Concise Introduction to Logic'' - 7th Edition&lt;br /&gt;
&lt;br /&gt;
* Kneale, W., and Kneale, M., (1962), ''The Development of Logic'', Oxford University Press, London, UK.&lt;br /&gt;
&lt;br /&gt;
* Priest, G. (2004), &amp;quot;Dialetheism&amp;quot;, ''Stanford Encyclopedia of Philosophy'', Edward N. Zalta (ed.), [http://plato.stanford.edu/entries/dialetheism Eprint].&lt;br /&gt;
&lt;br /&gt;
==See also== &lt;br /&gt;
* [[Course in Logic 101]] This takes the interested reader to every major page of the site.&lt;br /&gt;
* [[The Laws of Classical Logic]]  This page presents the axioms of classical logic&lt;br /&gt;
* [[Validity, Strength, Soundness and Cogency ]]&lt;br /&gt;
* [[Deductive and Inductive Logic]]&lt;br /&gt;
* [[Fallacies|Logical Fallacies]]&lt;br /&gt;
* [[Informal Fallacies]]  This page presents a list of informal fallacies found in arguments.&lt;br /&gt;
* [[Formal Fallacies]]&lt;br /&gt;
* [[Valid and Invalid Logical Forms]]&lt;br /&gt;
* [[Categorical Propositions]] &lt;br /&gt;
* [[Classical Logic]]&lt;br /&gt;
* [[Propositional Logic]] &lt;br /&gt;
* [[Predicate Logic]]&lt;br /&gt;
* [[Inductive Logic]] &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
[[Category:Logic]]&lt;br /&gt;
[[Category:Tutorials]]&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:13:46 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Main_Page</comments>		</item>
		<item>
			<title>Main Page</title>
			<link>http://72.14.177.54/logic/Main_Page</link>
			<description>&lt;p&gt;Admin:&amp;#32;/* References */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;==Introduction==&lt;br /&gt;
&lt;br /&gt;
This site is intended as a resource for those interested in learning Logic. While the author of this page will take a scholarly approach to the subject, this page will approach the subject in a more user friendly manner than available at Wikipedia, at times even using colloquial language. The site will offer a full [[Course in Logic 101]], based on two of the most reliable texts on logic: Copi and Cohen's ''Introduction to Logic (11th Edition)'' and Hurely's ''A Concise Introduction to Logic (7th Edition)''. The [[Course in Logic 101|course]] will cover the basics of Logic, [[Classical Logic]], [[Propositional Logic]], [[Predicate Logic]], [[Modal Logic]] and [[Inductive Logic]] including a discussion of [[Inductive Logic|Bayesian Theory]]. Those interested in taking the [[Course in Logic 101|course]] can consult that page for the proper order of reading the pages of this site.&lt;br /&gt;
&lt;br /&gt;
Now, let's begin.&lt;br /&gt;
&lt;br /&gt;
'''Logic''', (from the Greek word &amp;amp;lambda;&amp;amp;#972;&amp;amp;gamma;&amp;amp;omicron;&amp;amp;sigmaf; (''logos''), originally meaning ''the word'', but also referring to ''speech'' or ''reason'') is the science of evaluating the reasoning within [[Argument|arguments]].&lt;br /&gt;
&lt;br /&gt;
==Nature of logic==  &lt;br /&gt;
&lt;br /&gt;
Logic arose from a concern with correctness of [[argument]]ation (See [[Aristotle]]).  Logic is generally accepted and understood by logicians as a set of rules that tell us when an [[argument|argument's]] premises support their conclusion. Logic specifically deals with inferences whose validity can be traced back to the formal features of the representations that are involved in that inference.'' (Hofweber 2004).  &lt;br /&gt;
&lt;br /&gt;
Therefore, a further understanding of just what logic is, can be enhanced by delineating it from what it is not:&lt;br /&gt;
&lt;br /&gt;
*Logic is not the 'groundness of being' - that's metaphysics.&lt;br /&gt;
*Logic is not a set of laws that governs the universe - that's physics. &lt;br /&gt;
*Logic is not an immaterial &amp;quot;entity&amp;quot; that transcends reality - that's speculative theology.&lt;br /&gt;
*Logic is no a method for 'studying the world' -  that's science. &lt;br /&gt;
*Logic is not the method for assessing axioms - that's a matter of pure reason. &lt;br /&gt;
*Logic is not a way of evaluating 'truth' - that's philosophy. &lt;br /&gt;
*Logic is not a set of laws that governs human behavior - that's psychology. &lt;br /&gt;
*Logic is not even a study of how people reason - [[Non Logical Modes of Thought|Fortunately]] there is more to human reason than just logic.&lt;br /&gt;
&lt;br /&gt;
[[Immanuel Kant]] introduced an alternative idea as to what logic is.  He argued that logic should be conceived as the science of judgment, an idea taken up by [[Gottlob Frege]]. However, modern psychologists have demonstrated that a significant percentage of human judgment is clearly non logical.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Relation to other sciences===&lt;br /&gt;
&lt;br /&gt;
Closely related to logic is semantics, or the philosophy of language, which concerns the meaning of the words and sentences; epistemology, or the theory of knowledge, which concerns the conditions under which assertions are true; and the psychology of reasoning, which concerns the mental processes involved in reasoning.  Logic, however, is generally understood to describe reasoning in a prescriptive manner (i.e.  it describes how reasoning ought to take place), whereas psychology is descriptive and therefore more inclusive vis-a-vis the various methods of judgment humans actually use.  &lt;br /&gt;
&lt;br /&gt;
===Definition of an Argument===&lt;br /&gt;
&lt;br /&gt;
An [[argument]] is made up of a group  of statements we call [[proposition]]s. We use the term [[proposition]] instead of [[sentence]] because a proposition is more than just a sentence, it is a declarative sentence that contains a [[truth value]]. In the case of [[Classical Logic]], which is based on the [[Law of the Excluded Middle]], this truth value must  either be &amp;quot;true&amp;quot; or false&amp;quot; . &lt;br /&gt;
&lt;br /&gt;
There are two types of [[proposition]]s. The first, the [[Premises|Premise]], makes a commitment to truth, and is used as evidence to support the second type of proposition, the [[Conclusion]], which is the claim the arguer wants to prove. An argument must at least imply one of each. The study of logic, therefore, is the effort to determine the conditions under which one is justified in passing from the premises to the conclusion that logically must follow them.&lt;br /&gt;
&lt;br /&gt;
=== Examining Arguments: Informal, formal, and symbolic logic===&lt;br /&gt;
&lt;br /&gt;
Arguments can be examined through examining their premises, the form of the argument, and by looking at them abstractly. We use the terms &amp;quot;informal&amp;quot;, &amp;quot;formal&amp;quot; and &amp;quot;symbolic&amp;quot; to capture these meanings.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Informal Logic]]''' is the study of natural language [[Argument|arguments]].  The study of fallacies is an especially important branch of informal logic.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Formal Logic]]''' is the study of inference with purely formal content, where that content is made explicit. (An inference possesses a purely formal content if it can be expressed as a particular application of a wholly abstract rule, that is, a rule that is not about any particular thing or property.  We will see later that on many definitions of logic, logical inference and inference with purely formal content are the same thing.  This does not render the notion of informal logic vacuous, since one may wish to investigate logic without committing to a ''particular'' formal analysis.)&lt;br /&gt;
* '''[[Propositional Logic|Symbolic Logic]]''' is closely related to formal logic: it the study of symbolic abstractions that capture the formal features of logical inference.&lt;br /&gt;
&lt;br /&gt;
===Consistency, soundness, and completeness===&lt;br /&gt;
&lt;br /&gt;
There are three valuable properties that formal systems can have:&lt;br /&gt;
&lt;br /&gt;
:* '''[[Consistency]]''', which means that none of the theorems of the system contradict each other.&lt;br /&gt;
&lt;br /&gt;
:* '''[[Validity, Strength, Soundness and Cogency|Soundness]]''', which means that the system's rules of derivation will never let you infer anything false, so long as you start with only true premises.  So if a system is sound (and its axioms, if any, are true), then the theorems of a sound formal system are the [[truth]]s.  All of the theorems of a system that has no axioms are its truths and sometimes the truths of such a system are called 'logical truths.' (Note that if a system is not consistent, it cannot be sound. This is because a contradiction is always false, so if two theorems contradict at least one is false.)&lt;br /&gt;
&lt;br /&gt;
:* '''[[Completeness]]''', which means that there are no true sentences in the system that cannot, at least in principle, be proved using the derivation rules (and axioms, if any) of the system. &lt;br /&gt;
&lt;br /&gt;
Not all systems achieve all three virtues. It has been proven by [[Kurt Gödel]] that a system with enough axioms and/or rules of derivation to derive the principles of arithmetic cannot be both consistent and complete. This is called [[Gödel's Incompleteness Theorem]].&lt;br /&gt;
&lt;br /&gt;
===Deductive and inductive reasoning===&lt;br /&gt;
&lt;br /&gt;
Originally, logic consisted only of [[Deductive and Inductive Logic|deductive reasoning]] which concerns what follows universally from given premises.  However, it is important to note that [[Deductive and Inductive Logic|inductive reasoning]]&amp;amp;mdash;the study of deriving a reliable generalization from observations&amp;amp;mdash;has sometimes been included in the study of logic. Correspondingly, we must distinguish between deductive validity and inductive validity.  An inference is deductively valid if and only if there is no possible situation in which all the premises are true and the conclusion false.  The notion of deductive validity can be rigorously stated for systems of [[Formal and Informal Logic|formal logic]] in terms of the well-understood notions of [[semantics]].  Inductive validity on the other hand requires us to define a ''reliable generalization'' of some set of observations. The task of providing this definition may be approached  in various ways, some less formal than others; some of these definitions may use [[mathematical model]]s of probability.  For the most part this discussion of logic deals only with deductive logic.&lt;br /&gt;
&lt;br /&gt;
==Types of logic==&lt;br /&gt;
&lt;br /&gt;
Formal logic encompasses a wide variety of logical systems.  Various systems of logic include [[Classical Logic|Classical]] or [[Classical Logic|Syllogistic logic]], [[Predicate Logic]], [[Propositional Logic]], and [[Modal Logic]], and formal systems are indispensable in all branches of [[mathematical logic]].  &lt;br /&gt;
&lt;br /&gt;
===Syllogistic or Classical Logic===&lt;br /&gt;
&lt;br /&gt;
The ''Organon'' was [[Aristotle]]'s body of work on logic, with the ''Prior Analytics'' constituting the first explicit work in [[Formal and Informal Logic|formal logic]], introducing to the world the [[Syllogism|syllogism]]. [[Classical Logic|Syllogistic Logic]], [[Classical Logic|Term logic]], [[Classical Logic|Aristotelean Logic]] or [[Classical Logic]] are all references to the logical form of the [[Syllogism|syllogism]]. Syllogistic logic is the analysis of the judgments into propositions consisting of two terms that are related by one of a fixed number of relations, and the expression of inferences by means of [[syllogism]]s that consisted of two propositions sharing a common term as premise, and a conclusion which was a proposition involving the two unrelated terms from the premises.&lt;br /&gt;
&lt;br /&gt;
Aristotle's work was regarded in classical times and from medieval times in Europe and the Middle East as the very picture of a fully worked out system.  It was not alone: the [[Stoics]] proposed a system of [[Propositional Logic]] that was studied by medieval logicians; nor was the perfection of Aristotle's system undisputed; for example the [[problem of multiple generality]] was recognized in medieval times.  Nonetheless, problems with syllogistic logic were not seen as being in need of revolutionary solutions.&lt;br /&gt;
&lt;br /&gt;
Today, some academics claim that Aristotle's system is generally seen as having little more than historical value (though there is some current interest in extending term logics), regarded as made obsolete by the advent of [[Sentential Logic]] and the [[Predicate Logic|predicate calculus]].&lt;br /&gt;
&lt;br /&gt;
===Propositional Logic===&lt;br /&gt;
 &lt;br /&gt;
Logic as it is studied today is a very different subject from [[Classical Logic]];  the principal difference is the innovation of [[Propositional Logic]] and [[Predicate Logic]]. Propositional Logic allows for more complex argument forms than classical syllogisms. In propositional logic, propositions are represented by ''symbols'' and ''connectors'', so that the statement's logical form can be assessed for cases of truth and falsity, which in turn allows us to assess the entire argument's form for validity or invalidity. In symbolic, or propositional logic, a simple statement, containing one proposition, is is referred to as an ''atomic statement'', and is symbolized by one letter, such as p. A compound statement, with more than one proposition holding some relationship to another proposition, is referred to as a molecular statement, which may be symbolized as p v q. The v symbol just used is a connective: Atomic propositions become molecular propositions when they are joined by connectives. &lt;br /&gt;
&lt;br /&gt;
===Predicate Logic===&lt;br /&gt;
&lt;br /&gt;
However, just as limits in Classical Logical led to [[Propositional Logic]], limits in Propositional Logic pointed to the need for a new logic. Propositional Logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument:&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal&lt;br /&gt;
    * Socrates is a man&lt;br /&gt;
    * Therefore, Socrates is mortal&lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A&lt;br /&gt;
    * B&lt;br /&gt;
    * ∴ C (∴ means &amp;quot;therefore&amp;quot;&lt;br /&gt;
&lt;br /&gt;
which is invalid, because there are no connectors between the premises and between the premises and the conclusion.&lt;br /&gt;
&lt;br /&gt;
Therefore, the need for a ''First Order'', or [[Predicate Logic]] became apparent. The new ingredient of first-order logic not found in propositional logic is [[Predicate Logic|quantification]]: where φ is any (well-formed) formula, the new constructions ∀x φ and ∃x φ — read &amp;quot;for all x, φ&amp;quot; and &amp;quot;for some x, φ&amp;quot; — are introduced, where x is an individual variable whose range is the set of individuals of some given universe of discourse (or domain). For example, if the universe consists solely of people, then x ranges over people. For convenience, we write φ as φ(x) to show that it contains only the variable x free and, for b a member of the universe, we let φ[b] express that b satisfies (i.e. has the property expressed by) φ. Then ∀x φ(x) states that φ[b] is true for every b in the universe, and ∃x φ(x) means that there is a b (in the universe) such that φ[b] holds.&lt;br /&gt;
&lt;br /&gt;
The argument about Socrates can be formalized in first-order logic as follows. Let the universe of discourse be the set of all people, living and deceased, and let Man(x) be a predicate (which, informally, means that the person represented by variable x is a man) and Mortal(x) be a second predicate. Then the argument above becomes&lt;br /&gt;
&lt;br /&gt;
    * ∀ x (Man(x) → Mortal(x))&lt;br /&gt;
    * Man(Socrates)&lt;br /&gt;
    * ∴ Mortal(Socrates)&lt;br /&gt;
&lt;br /&gt;
A literal translation of the first line would be &amp;quot;For all x, if x is described by 'Man', x must also be described by 'Mortal'.&amp;quot; The second line states that the predicate &amp;quot;Man&amp;quot; applies to Socrates, and the third line translates to &amp;quot;Therefore, the description 'Mortal' applies to Socrates.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Modal logic===&lt;br /&gt;
&lt;br /&gt;
In language, [[modality]] deals with the phenomenon that subparts of a sentence may have their semantics modified by special verbs or modal particles.  For example, &amp;quot;''We go to the games''&amp;quot; can be modified to give &amp;quot;''We should go to the games''&amp;quot;, and &amp;quot;''We can go to the games''&amp;quot;&amp;quot; and perhaps &amp;quot;''We will go to the games''&amp;quot;.  More abstractly, we might say that modality affects the circumstances in which we take an assertion to be satisfied.&lt;br /&gt;
&lt;br /&gt;
The logical study of modality dates back to [[Aristotle]], who was concerned with the [[alethic modalities]] of necessity and possibility, which he observed to be dual in the sense of [[De Morgan duality]].  While the study of necessity and possibility remained important to philosophers, little logical innovation happened until the landmark investigations of [[Clarence Irving Lewis]] in [[1918]], who formulated a family of rival axiomatisations of the alethic modalities.  His work unleashed a torrent of new work on the topic, expanding the kinds of modality treated to include [[deontic logic]] and [[epistemic logic]].  The seminal work of [[Arthur Prior]] applied the same formal language to treat [[temporal logic]] and paved the way for the marriage of the two subjects.  [[Saul Kripke]] discovered (contemporaneously with rivals) his theory of [[frame semantics]] which revolutionized the formal technology available to modal logicians and gave a new [[graph theory|graph-theoretic]] way of looking at modality that has driven many applications in [[computational linguistics]] and [[computer science]], such as [[dynamic logic]].&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
Students following the [[Course in Logic 101]] should proceed to the section entitled: [[The Laws of Classical Logic]]&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
 &lt;br /&gt;
&lt;br /&gt;
* Copi, I. M, Cohen, C., (2001), ''Introduction to Logic'', 11th Edition.&lt;br /&gt;
&lt;br /&gt;
* Gabbay, D.M., and Guenthner, F. (eds., 2001-2005), ''Handbook of Philosophical Logic'', 13 vols., 2nd edition, Kluwer Publishers, Dordrecht.&lt;br /&gt;
&lt;br /&gt;
* [[David Hilbert|Hilbert, D.]], and Ackermann, W. (1928), ''Grundzüge der theoretischen Logik'' (''[[Principles of Theoretical Logic]]''), Springer-Verlag.&lt;br /&gt;
&lt;br /&gt;
* Hodges, W. (2001), ''Logic.  An introduction to Elementary Logic'', Penguin Books.&lt;br /&gt;
&lt;br /&gt;
* Hofweber, T. (2004), &amp;quot;Logic and Ontology&amp;quot;, ''[[Stanford Encyclopedia of Philosophy]]'', [[Edward N. Zalta]] (ed.), [http://plato.stanford.edu/entries/logic-ontology/ Eprint].&lt;br /&gt;
&lt;br /&gt;
* Hughes, R.I.G. (ed., 1993), ''A Philosophical Companion to First-Order Logic'', Hackett Publishing.&lt;br /&gt;
&lt;br /&gt;
* Hurely, P. J.  (2000) ''A Concise Introduction to Logic'' - 7th Edition&lt;br /&gt;
&lt;br /&gt;
* [[William Kneale|Kneale, William]], and [[Martha Kneale|Kneale, Martha]], (1962), ''The Development of Logic'', Oxford University Press, London, UK.&lt;br /&gt;
&lt;br /&gt;
* [[Graham Priest|Priest, Graham]] (2004), &amp;quot;Dialetheism&amp;quot;, ''Stanford Encyclopedia of Philosophy'', Edward N. Zalta (ed.), [http://plato.stanford.edu/entries/dialetheism Eprint].&lt;br /&gt;
&lt;br /&gt;
==See also== &lt;br /&gt;
* [[Course in Logic 101]] This takes the interested reader to every major page of the site.&lt;br /&gt;
* [[The Laws of Classical Logic]]  This page presents the axioms of classical logic&lt;br /&gt;
* [[Validity, Strength, Soundness and Cogency ]]&lt;br /&gt;
* [[Deductive and Inductive Logic]]&lt;br /&gt;
* [[Fallacies|Logical Fallacies]]&lt;br /&gt;
* [[Informal Fallacies]]  This page presents a list of informal fallacies found in arguments.&lt;br /&gt;
* [[Formal Fallacies]]&lt;br /&gt;
* [[Valid and Invalid Logical Forms]]&lt;br /&gt;
* [[Categorical Propositions]] &lt;br /&gt;
* [[Classical Logic]]&lt;br /&gt;
* [[Propositional Logic]] &lt;br /&gt;
* [[Predicate Logic]]&lt;br /&gt;
* [[Inductive Logic]] &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
[[Category:Logic]]&lt;br /&gt;
[[Category:Tutorials]]&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:12:50 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Main_Page</comments>		</item>
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			<title>Main Page</title>
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&lt;div&gt;==Introduction==&lt;br /&gt;
&lt;br /&gt;
This site is intended as a resource for those interested in learning Logic. While the author of this page will take a scholarly approach to the subject, this page will approach the subject in a more user friendly manner than available at Wikipedia, at times even using colloquial language. The site will offer a full [[Course in Logic 101]], based on two of the most reliable texts on logic: Copi and Cohen's ''Introduction to Logic (11th Edition)'' and Hurely's ''A Concise Introduction to Logic (7th Edition)''. The [[Course in Logic 101|course]] will cover the basics of Logic, [[Classical Logic]], [[Propositional Logic]], [[Predicate Logic]], [[Modal Logic]] and [[Inductive Logic]] including a discussion of [[Inductive Logic|Bayesian Theory]]. Those interested in taking the [[Course in Logic 101|course]] can consult that page for the proper order of reading the pages of this site.&lt;br /&gt;
&lt;br /&gt;
Now, let's begin.&lt;br /&gt;
&lt;br /&gt;
'''Logic''', (from the Greek word &amp;amp;lambda;&amp;amp;#972;&amp;amp;gamma;&amp;amp;omicron;&amp;amp;sigmaf; (''logos''), originally meaning ''the word'', but also referring to ''speech'' or ''reason'') is the science of evaluating the reasoning within [[Argument|arguments]].&lt;br /&gt;
&lt;br /&gt;
==Nature of logic==  &lt;br /&gt;
&lt;br /&gt;
Logic arose from a concern with correctness of [[argument]]ation (See [[Aristotle]]).  Logic is generally accepted and understood by logicians as a set of rules that tell us when an [[argument|argument's]] premises support their conclusion. Logic specifically deals with inferences whose validity can be traced back to the formal features of the representations that are involved in that inference.'' (Hofweber 2004).  &lt;br /&gt;
&lt;br /&gt;
Therefore, a further understanding of just what logic is, can be enhanced by delineating it from what it is not:&lt;br /&gt;
&lt;br /&gt;
*Logic is not the 'groundness of being' - that's metaphysics.&lt;br /&gt;
*Logic is not a set of laws that governs the universe - that's physics. &lt;br /&gt;
*Logic is not an immaterial &amp;quot;entity&amp;quot; that transcends reality - that's speculative theology.&lt;br /&gt;
*Logic is no a method for 'studying the world' -  that's science. &lt;br /&gt;
*Logic is not the method for assessing axioms - that's a matter of pure reason. &lt;br /&gt;
*Logic is not a way of evaluating 'truth' - that's philosophy. &lt;br /&gt;
*Logic is not a set of laws that governs human behavior - that's psychology. &lt;br /&gt;
*Logic is not even a study of how people reason - [[Non Logical Modes of Thought|Fortunately]] there is more to human reason than just logic.&lt;br /&gt;
&lt;br /&gt;
[[Immanuel Kant]] introduced an alternative idea as to what logic is.  He argued that logic should be conceived as the science of judgment, an idea taken up by [[Gottlob Frege]]. However, modern psychologists have demonstrated that a significant percentage of human judgment is clearly non logical.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Relation to other sciences===&lt;br /&gt;
&lt;br /&gt;
Closely related to logic is semantics, or the philosophy of language, which concerns the meaning of the words and sentences; epistemology, or the theory of knowledge, which concerns the conditions under which assertions are true; and the psychology of reasoning, which concerns the mental processes involved in reasoning.  Logic, however, is generally understood to describe reasoning in a prescriptive manner (i.e.  it describes how reasoning ought to take place), whereas psychology is descriptive and therefore more inclusive vis-a-vis the various methods of judgment humans actually use.  &lt;br /&gt;
&lt;br /&gt;
===Definition of an Argument===&lt;br /&gt;
&lt;br /&gt;
An [[argument]] is made up of a group  of statements we call [[proposition]]s. We use the term [[proposition]] instead of [[sentence]] because a proposition is more than just a sentence, it is a declarative sentence that contains a [[truth value]]. In the case of [[Classical Logic]], which is based on the [[Law of the Excluded Middle]], this truth value must  either be &amp;quot;true&amp;quot; or false&amp;quot; . &lt;br /&gt;
&lt;br /&gt;
There are two types of [[proposition]]s. The first, the [[Premises|Premise]], makes a commitment to truth, and is used as evidence to support the second type of proposition, the [[Conclusion]], which is the claim the arguer wants to prove. An argument must at least imply one of each. The study of logic, therefore, is the effort to determine the conditions under which one is justified in passing from the premises to the conclusion that logically must follow them.&lt;br /&gt;
&lt;br /&gt;
=== Examining Arguments: Informal, formal, and symbolic logic===&lt;br /&gt;
&lt;br /&gt;
Arguments can be examined through examining their premises, the form of the argument, and by looking at them abstractly. We use the terms &amp;quot;informal&amp;quot;, &amp;quot;formal&amp;quot; and &amp;quot;symbolic&amp;quot; to capture these meanings.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Informal Logic]]''' is the study of natural language [[Argument|arguments]].  The study of fallacies is an especially important branch of informal logic.&lt;br /&gt;
&lt;br /&gt;
* '''[[Formal and Informal Logic|Formal Logic]]''' is the study of inference with purely formal content, where that content is made explicit. (An inference possesses a purely formal content if it can be expressed as a particular application of a wholly abstract rule, that is, a rule that is not about any particular thing or property.  We will see later that on many definitions of logic, logical inference and inference with purely formal content are the same thing.  This does not render the notion of informal logic vacuous, since one may wish to investigate logic without committing to a ''particular'' formal analysis.)&lt;br /&gt;
* '''[[Propositional Logic|Symbolic Logic]]''' is closely related to formal logic: it the study of symbolic abstractions that capture the formal features of logical inference.&lt;br /&gt;
&lt;br /&gt;
===Consistency, soundness, and completeness===&lt;br /&gt;
&lt;br /&gt;
There are three valuable properties that formal systems can have:&lt;br /&gt;
&lt;br /&gt;
:* '''[[Consistency]]''', which means that none of the theorems of the system contradict each other.&lt;br /&gt;
&lt;br /&gt;
:* '''[[Validity, Strength, Soundness and Cogency|Soundness]]''', which means that the system's rules of derivation will never let you infer anything false, so long as you start with only true premises.  So if a system is sound (and its axioms, if any, are true), then the theorems of a sound formal system are the [[truth]]s.  All of the theorems of a system that has no axioms are its truths and sometimes the truths of such a system are called 'logical truths.' (Note that if a system is not consistent, it cannot be sound. This is because a contradiction is always false, so if two theorems contradict at least one is false.)&lt;br /&gt;
&lt;br /&gt;
:* '''[[Completeness]]''', which means that there are no true sentences in the system that cannot, at least in principle, be proved using the derivation rules (and axioms, if any) of the system. &lt;br /&gt;
&lt;br /&gt;
Not all systems achieve all three virtues. It has been proven by [[Kurt Gödel]] that a system with enough axioms and/or rules of derivation to derive the principles of arithmetic cannot be both consistent and complete. This is called [[Gödel's Incompleteness Theorem]].&lt;br /&gt;
&lt;br /&gt;
===Deductive and inductive reasoning===&lt;br /&gt;
&lt;br /&gt;
Originally, logic consisted only of [[Deductive and Inductive Logic|deductive reasoning]] which concerns what follows universally from given premises.  However, it is important to note that [[Deductive and Inductive Logic|inductive reasoning]]&amp;amp;mdash;the study of deriving a reliable generalization from observations&amp;amp;mdash;has sometimes been included in the study of logic. Correspondingly, we must distinguish between deductive validity and inductive validity.  An inference is deductively valid if and only if there is no possible situation in which all the premises are true and the conclusion false.  The notion of deductive validity can be rigorously stated for systems of [[Formal and Informal Logic|formal logic]] in terms of the well-understood notions of [[semantics]].  Inductive validity on the other hand requires us to define a ''reliable generalization'' of some set of observations. The task of providing this definition may be approached  in various ways, some less formal than others; some of these definitions may use [[mathematical model]]s of probability.  For the most part this discussion of logic deals only with deductive logic.&lt;br /&gt;
&lt;br /&gt;
==Types of logic==&lt;br /&gt;
&lt;br /&gt;
Formal logic encompasses a wide variety of logical systems.  Various systems of logic include [[Classical Logic|Classical]] or [[Classical Logic|Syllogistic logic]], [[Predicate Logic]], [[Propositional Logic]], and [[Modal Logic]], and formal systems are indispensable in all branches of [[mathematical logic]].  &lt;br /&gt;
&lt;br /&gt;
===Syllogistic or Classical Logic===&lt;br /&gt;
&lt;br /&gt;
The ''Organon'' was [[Aristotle]]'s body of work on logic, with the ''Prior Analytics'' constituting the first explicit work in [[Formal and Informal Logic|formal logic]], introducing to the world the [[Syllogism|syllogism]]. [[Classical Logic|Syllogistic Logic]], [[Classical Logic|Term logic]], [[Classical Logic|Aristotelean Logic]] or [[Classical Logic]] are all references to the logical form of the [[Syllogism|syllogism]]. Syllogistic logic is the analysis of the judgments into propositions consisting of two terms that are related by one of a fixed number of relations, and the expression of inferences by means of [[syllogism]]s that consisted of two propositions sharing a common term as premise, and a conclusion which was a proposition involving the two unrelated terms from the premises.&lt;br /&gt;
&lt;br /&gt;
Aristotle's work was regarded in classical times and from medieval times in Europe and the Middle East as the very picture of a fully worked out system.  It was not alone: the [[Stoics]] proposed a system of [[Propositional Logic]] that was studied by medieval logicians; nor was the perfection of Aristotle's system undisputed; for example the [[problem of multiple generality]] was recognized in medieval times.  Nonetheless, problems with syllogistic logic were not seen as being in need of revolutionary solutions.&lt;br /&gt;
&lt;br /&gt;
Today, some academics claim that Aristotle's system is generally seen as having little more than historical value (though there is some current interest in extending term logics), regarded as made obsolete by the advent of [[Sentential Logic]] and the [[Predicate Logic|predicate calculus]].&lt;br /&gt;
&lt;br /&gt;
===Propositional Logic===&lt;br /&gt;
 &lt;br /&gt;
Logic as it is studied today is a very different subject from [[Classical Logic]];  the principal difference is the innovation of [[Propositional Logic]] and [[Predicate Logic]]. Propositional Logic allows for more complex argument forms than classical syllogisms. In propositional logic, propositions are represented by ''symbols'' and ''connectors'', so that the statement's logical form can be assessed for cases of truth and falsity, which in turn allows us to assess the entire argument's form for validity or invalidity. In symbolic, or propositional logic, a simple statement, containing one proposition, is is referred to as an ''atomic statement'', and is symbolized by one letter, such as p. A compound statement, with more than one proposition holding some relationship to another proposition, is referred to as a molecular statement, which may be symbolized as p v q. The v symbol just used is a connective: Atomic propositions become molecular propositions when they are joined by connectives. &lt;br /&gt;
&lt;br /&gt;
===Predicate Logic===&lt;br /&gt;
&lt;br /&gt;
However, just as limits in Classical Logical led to [[Propositional Logic]], limits in Propositional Logic pointed to the need for a new logic. Propositional Logic is not adequate for formalizing valid arguments that rely on the internal structure of the propositions involved. For example, a translation of the valid argument:&lt;br /&gt;
&lt;br /&gt;
    * All men are mortal&lt;br /&gt;
    * Socrates is a man&lt;br /&gt;
    * Therefore, Socrates is mortal&lt;br /&gt;
&lt;br /&gt;
into propositional logic yields&lt;br /&gt;
&lt;br /&gt;
    * A&lt;br /&gt;
    * B&lt;br /&gt;
    * ∴ C (∴ means &amp;quot;therefore&amp;quot;&lt;br /&gt;
&lt;br /&gt;
which is invalid, because there are no connectors between the premises and between the premises and the conclusion.&lt;br /&gt;
&lt;br /&gt;
Therefore, the need for a ''First Order'', or [[Predicate Logic]] became apparent. The new ingredient of first-order logic not found in propositional logic is [[Predicate Logic|quantification]]: where φ is any (well-formed) formula, the new constructions ∀x φ and ∃x φ — read &amp;quot;for all x, φ&amp;quot; and &amp;quot;for some x, φ&amp;quot; — are introduced, where x is an individual variable whose range is the set of individuals of some given universe of discourse (or domain). For example, if the universe consists solely of people, then x ranges over people. For convenience, we write φ as φ(x) to show that it contains only the variable x free and, for b a member of the universe, we let φ[b] express that b satisfies (i.e. has the property expressed by) φ. Then ∀x φ(x) states that φ[b] is true for every b in the universe, and ∃x φ(x) means that there is a b (in the universe) such that φ[b] holds.&lt;br /&gt;
&lt;br /&gt;
The argument about Socrates can be formalized in first-order logic as follows. Let the universe of discourse be the set of all people, living and deceased, and let Man(x) be a predicate (which, informally, means that the person represented by variable x is a man) and Mortal(x) be a second predicate. Then the argument above becomes&lt;br /&gt;
&lt;br /&gt;
    * ∀ x (Man(x) → Mortal(x))&lt;br /&gt;
    * Man(Socrates)&lt;br /&gt;
    * ∴ Mortal(Socrates)&lt;br /&gt;
&lt;br /&gt;
A literal translation of the first line would be &amp;quot;For all x, if x is described by 'Man', x must also be described by 'Mortal'.&amp;quot; The second line states that the predicate &amp;quot;Man&amp;quot; applies to Socrates, and the third line translates to &amp;quot;Therefore, the description 'Mortal' applies to Socrates.&amp;quot;&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
===Modal logic===&lt;br /&gt;
&lt;br /&gt;
In language, [[modality]] deals with the phenomenon that subparts of a sentence may have their semantics modified by special verbs or modal particles.  For example, &amp;quot;''We go to the games''&amp;quot; can be modified to give &amp;quot;''We should go to the games''&amp;quot;, and &amp;quot;''We can go to the games''&amp;quot;&amp;quot; and perhaps &amp;quot;''We will go to the games''&amp;quot;.  More abstractly, we might say that modality affects the circumstances in which we take an assertion to be satisfied.&lt;br /&gt;
&lt;br /&gt;
The logical study of modality dates back to [[Aristotle]], who was concerned with the [[alethic modalities]] of necessity and possibility, which he observed to be dual in the sense of [[De Morgan duality]].  While the study of necessity and possibility remained important to philosophers, little logical innovation happened until the landmark investigations of [[Clarence Irving Lewis]] in [[1918]], who formulated a family of rival axiomatisations of the alethic modalities.  His work unleashed a torrent of new work on the topic, expanding the kinds of modality treated to include [[deontic logic]] and [[epistemic logic]].  The seminal work of [[Arthur Prior]] applied the same formal language to treat [[temporal logic]] and paved the way for the marriage of the two subjects.  [[Saul Kripke]] discovered (contemporaneously with rivals) his theory of [[frame semantics]] which revolutionized the formal technology available to modal logicians and gave a new [[graph theory|graph-theoretic]] way of looking at modality that has driven many applications in [[computational linguistics]] and [[computer science]], such as [[dynamic logic]].&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
Students following the [[Course in Logic 101]] should proceed to the section entitled: [[The Laws of Classical Logic]]&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
 &lt;br /&gt;
* Gabbay, D.M., and Guenthner, F. (eds., 2001-2005), ''Handbook of Philosophical Logic'', 13 vols., 2nd edition, Kluwer Publishers, Dordrecht.&lt;br /&gt;
&lt;br /&gt;
* [[Vincent F. Hendricks]], ''Thought 2 Talk: A Crash Course in Reflection and Expression'', New York: Automatic Press / VIP, 2005, ISBN 8799101378&lt;br /&gt;
&lt;br /&gt;
* [[David Hilbert|Hilbert, D.]], and Ackermann, W. (1928), ''Grundzüge der theoretischen Logik'' (''[[Principles of Theoretical Logic]]''), Springer-Verlag.&lt;br /&gt;
&lt;br /&gt;
* Hodges, W. (2001), ''Logic.  An introduction to Elementary Logic'', Penguin Books.&lt;br /&gt;
&lt;br /&gt;
* Hofweber, T. (2004), &amp;quot;Logic and Ontology&amp;quot;, ''[[Stanford Encyclopedia of Philosophy]]'', [[Edward N. Zalta]] (ed.), [http://plato.stanford.edu/entries/logic-ontology/ Eprint].&lt;br /&gt;
&lt;br /&gt;
* Hughes, R.I.G. (ed., 1993), ''A Philosophical Companion to First-Order Logic'', Hackett Publishing.&lt;br /&gt;
&lt;br /&gt;
* [[William Kneale|Kneale, William]], and [[Martha Kneale|Kneale, Martha]], (1962), ''The Development of Logic'', Oxford University Press, London, UK.&lt;br /&gt;
&lt;br /&gt;
* [[Graham Priest|Priest, Graham]] (2004), &amp;quot;Dialetheism&amp;quot;, ''Stanford Encyclopedia of Philosophy'', Edward N. Zalta (ed.), [http://plato.stanford.edu/entries/dialetheism Eprint].&lt;br /&gt;
&lt;br /&gt;
==See also== &lt;br /&gt;
* [[Course in Logic 101]] This takes the interested reader to every major page of the site.&lt;br /&gt;
* [[The Laws of Classical Logic]]  This page presents the axioms of classical logic&lt;br /&gt;
* [[Validity, Strength, Soundness and Cogency ]]&lt;br /&gt;
* [[Deductive and Inductive Logic]]&lt;br /&gt;
* [[Fallacies|Logical Fallacies]]&lt;br /&gt;
* [[Informal Fallacies]]  This page presents a list of informal fallacies found in arguments.&lt;br /&gt;
* [[Formal Fallacies]]&lt;br /&gt;
* [[Valid and Invalid Logical Forms]]&lt;br /&gt;
* [[Categorical Propositions]] &lt;br /&gt;
* [[Classical Logic]]&lt;br /&gt;
* [[Propositional Logic]] &lt;br /&gt;
* [[Predicate Logic]]&lt;br /&gt;
* [[Inductive Logic]] &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
[[Category:Logic]]&lt;br /&gt;
[[Category:Tutorials]]&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:10:55 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Main_Page</comments>		</item>
		<item>
			<title>Fallacies</title>
			<link>http://72.14.177.54/logic/Fallacies</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;''Fallacies'' are fatal flaws in a logical [[argument]] - these flaws invalidate the entire argument, ''no matter the real truth value of the conclusion of the argument,'' because the existence of a fallacy in an argument indicates that the argument is incapable of proving support for the arguer's contention.&lt;br /&gt;
&lt;br /&gt;
There are two different categories of fallacies - Formal and informal.&lt;br /&gt;
&lt;br /&gt;
[[Formal Fallacies]] - All arguments can be broken down into general forms according to the way the premises are presented. Some of these forms are valid, and others invalid. In order to understand these forms, background information regarding the argument &amp;quot;forms&amp;quot; must first be presented. Accordingly, this will be dealt with in a following section&lt;br /&gt;
&lt;br /&gt;
[[Informal Fallacies]] in order to identify informal fallacies, an analysis of the content of an argument must be undertaken directly. An argument may possess a valid form, but may make an informal fallacy. &lt;br /&gt;
&lt;br /&gt;
----&lt;br /&gt;
&lt;br /&gt;
==References==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
Hurely, P. J.  (2000) A Concise Introduction to Logic - 7th Edition&lt;/div&gt;</description>
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		<item>
			<title>Necessity and Contingency</title>
			<link>http://72.14.177.54/logic/Necessity_and_Contingency</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Necessary and Contingent Truth&lt;br /&gt;
&lt;br /&gt;
For every argument there corresponds a conditional statement whose antecedent is the conjunction of the argument's premise and whose consequent is the argument's conclusion. For example, an argument using the form of modus ponens:&lt;br /&gt;
&lt;br /&gt;
p ⊃ q&lt;br /&gt;
p&lt;br /&gt;
therefore q&lt;br /&gt;
&lt;br /&gt;
...could be expressed as a conditional statement thusly: ''[(p ⊃ q) &amp;amp; p] ⊃ q''. We can read this conditional statement this way: &amp;quot;If it is true that 'p is true, then q is true' AND p is in fact true, then in this case, q is true.&amp;quot;  &lt;br /&gt;
&lt;br /&gt;
Now why go through all this? Because something very interesting happens to a valid deductive argument when stated in a conditional statement: it becomes a [[Tautology|tautology]]. We learn then that a deductive argument is valid if and only if its expression in the form of a conditional statement is a ''tautology''.&lt;br /&gt;
&lt;br /&gt;
This all goes back to my original expostulation on the nature of [[Deductive and Inductive Logic|deductive arguments]]: deductive arguments  deal in equivalencies, in equalities, i.e. with[[ a priori truths]]. &lt;br /&gt;
&lt;br /&gt;
So how do we deal with inductive matters, with matters that concern real world phenomena?&lt;br /&gt;
&lt;br /&gt;
Here, we can only deal in ''contingent truths''. If we think back to the deductively invalid forms of [[affirming the antecedent]] and [[denying the consequent]], we will recall while there were possible permutations where all true premises led to a false conclusion, we also can recall that there were permutations where this was not the case. Therefore, along with necessarily contradictory conclusions, these deductively invalid forms also led to contingent truths: claims that may in fact be true. As we will see in the section on inductive logic, we can rely on such forms to give us probable or possible truths.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:07:37 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Necessity_and_Contingency</comments>		</item>
		<item>
			<title>Necessity and Contingency</title>
			<link>http://72.14.177.54/logic/Necessity_and_Contingency</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;Necessary and Contingent Truth&lt;br /&gt;
&lt;br /&gt;
For every argument there corresponds a conditional statement whose antecedent is the conjunction of the argument's premise and whose consequent is the argument's conclusion. For example, an argument using the form of modus ponens:&lt;br /&gt;
&lt;br /&gt;
p ⊃ q&lt;br /&gt;
p&lt;br /&gt;
therefore q&lt;br /&gt;
&lt;br /&gt;
...could be expressed as a conditional statement thusly: ''[(p ⊃ q) &amp;amp; p] ⊃ q''. We can read this conditional statement this way: &amp;quot;If it is true that 'p is true, then q is true' AND p is in fact true, then in this case, q is true.&amp;quot;  &lt;br /&gt;
&lt;br /&gt;
Now why go through all this? Because something very interesting happens to a valid deductive argument when stated in a conditional statement: it becomes a [[Tautology|tautology]]. We learn then that a deductive argument is valid if and only if its expression in the form of a conditional statement is a ''tautology''.&lt;br /&gt;
&lt;br /&gt;
This all goes back to my original expostulation on the nature of [[Deductive and Inductive Logic|deductive arguments]]: deductive arguments  deal in equivalencies, in equalities, i.e. with[[ a priori truths]]. &lt;br /&gt;
&lt;br /&gt;
So how do we deal with inductive matters, with matters that concern real world phenomena?&lt;br /&gt;
&lt;br /&gt;
Here, we can only deal in ''contingent truths''. If we think back to the deductively invalid forms of [[affirming the antecedant]] and [[denying the consequent]], we will recall while there were possible permutations where all true premises led to a false conclusion, we also can recall that there were permutations where this was not the case. Therefore, along with necessarily contradictory conclusions, these deductively invalid forms also led to contingent truths: claims that may in fact be true. As we will see in the section on inductive logic, we can rely on such forms to give us probable or possible truths.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:07:24 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Necessity_and_Contingency</comments>		</item>
		<item>
			<title>Rhetoric</title>
			<link>http://72.14.177.54/logic/Rhetoric</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;The wily Dr. Smith can hardly approve of argument based on mere emotional persuasion. But I am sure he can understand why I have chosen to speak on rhetoric...&lt;br /&gt;
&lt;br /&gt;
http://www.candleinthedark.com/drsmith_rhetoric.jpg&lt;br /&gt;
&lt;br /&gt;
Ever since I began the logic subpage, I have naturally considered sources that only deal with the subject of logic. Recently, I have decided this was a mistake.&lt;br /&gt;
&lt;br /&gt;
My feeling now is that in order to really delineate logic from other modes of persuasion, I would need to specifically point out the other methods. This has led to my addition of a Sophistry section - on the art of rhetoric.&lt;br /&gt;
&lt;br /&gt;
==A little history on the Sophists - the first advocates of rhetoric==&lt;br /&gt;
&lt;br /&gt;
The ancient Greek Sophists were the first organized group of philosophers to point out the fallacy of naive empiricism - the natural assumption that what we take in with our senses represents the totality of reality, without error. The Sophists argued that in a rapidly changing and evolving world, no one could get a true reading on reality. As Heraclitus said: How can we know anything in a world that never is, but instead is always becoming something else? While many Sophists, such as Gorgias took this to the extreme of nihilism, denying that anyone could ever know anything (so, how did he know that?), all sophists agreed that our view of reality was at best subjective, prone to error, and not capable of creating certain premises for logical arguments. Today we tend to agree with the Sophists on this point.&lt;br /&gt;
&lt;br /&gt;
Since empirical evidence was flawed at its root, the Sophists claimed that the only valid means of persuasion was rhetoric - an appeal to our emotions. Rhetorical appeals clearly had benefits over empiricism - we could be more certain of our own emotions, and they could be counted on to motivate us to action.&lt;br /&gt;
&lt;br /&gt;
The Sophists took this view to &amp;quot;heart' and became experts in the use of rhetoric, to the point that it irritated their enemies - who then became desperate to find something that could be certain - i.e.: clear, unchanging and perfect, that would be suitable for a premise.&lt;br /&gt;
&lt;br /&gt;
Soon, Socrates would come up with the idea of reals, a mental construct of reality, that suited this need. Eventually, the concept of reals would be used in [[Aristotle]]'s art of logic. Since the school of the rationalists and the empiricists won out over the Sophists, and, as history is written by the victors, the Sophists would come to be seen in disparaging terms, to the point that the words sophistry and rhetoric now have negative connotations, even amongst the common man.&lt;br /&gt;
&lt;br /&gt;
However, to be fair, it should be stated that rhetoric does have a value - and in fact, this is recognized by its still popular use today - mostly in the hands of (not, surprisingly) lawyers and politicians. While the extreme skepticism of the sophists is in disfavor, (Betrand Russell makes the point that I inferred above, that extreme skepticism is merely a dogmatic belief system, and as such prone to error itself) it would do us good to know the methods of the sophists today.&lt;br /&gt;
&lt;br /&gt;
So, in order to better explain the value of logic, and to explain how politicians work, I have listed the basics of what I consider to be the inferior tool of rhetoric here: &lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==Rhetoric - The use of persuasive words to win an argument==&lt;br /&gt;
&lt;br /&gt;
There are two general ways to argue, although both forms are not necessarily mutually exclusive. The first is through logical argument, the second, through rhetorical persuasion. In logic, we attempt to convince through logical necessity - if one accepts our premises, they must accept our conclusions. While emotions of course play a part, they are not directly appealed to. When one attempts to persuade as opposed to convince, they rely more on emotion than on logic.&lt;br /&gt;
&lt;br /&gt;
Therefore, in rhetoric, we refers to &amp;quot;premises&amp;quot; as appeals. When one wants to appeal to another's emotions, they call upon different strategies - they attempt to personalize the argument, appeal to our own vanities. Here are some of the most common methods:&lt;br /&gt;
&lt;br /&gt;
===Anecdotes, Stories, Metaphors===&lt;br /&gt;
&lt;br /&gt;
These cast an issue in a favorable or unfavorable light, or can highlight or suppress certain aspects. They work by suggesting a likeness between a character and the listener, or a situation and the listener's. &lt;br /&gt;
&lt;br /&gt;
In logic we see that this appeal often commits the errors of the small sample bias, weak comparison, and excluded middle.&lt;br /&gt;
&lt;br /&gt;
===Double-bind===&lt;br /&gt;
&lt;br /&gt;
One way of getting a child to eat her vegetables is to offer a &amp;quot;choice&amp;quot; &amp;quot;Would you like peas or spinach?&amp;quot; Regardless of the alternative chosen, your desired objective is met. &amp;quot;Which kind of environmental bureaucracy do you want -- one that stifles business and innovation, or one that burdens American industry with impossible extra costs?&amp;quot; &lt;br /&gt;
&lt;br /&gt;
In logic we see that this appeal often commits the false dichotomy error.&lt;br /&gt;
&lt;br /&gt;
===Contingency===&lt;br /&gt;
&lt;br /&gt;
This works by getting you to accept both parts of a statement because of how they are linked; one part might be reasonable enough by itself, but. . . &amp;quot;Unless you want the earth to turn to a barren crust, you must oppose corporate capitalist pigs, tooth and nail.&amp;quot; &lt;br /&gt;
&lt;br /&gt;
In logic we see that this appeal often commits the logical error of false dichotomy or hasty generalization.&lt;br /&gt;
&lt;br /&gt;
===Rapport===&lt;br /&gt;
&lt;br /&gt;
How does the author go about building a sense of friendliness and receptivity on the part of the audience? Some methods are friendly introductions (&amp;quot;my friends&amp;quot;), complimenting, showing respect, speaking the speakers 'language,' and conveying optimism. These are important communicative techniques! Rapport is important. We just have to be aware of its use in persuasive contexts. Used car salesmen use rapport. In logic we see that this appeal often commits the Red Herring Fallacy.&lt;br /&gt;
&lt;br /&gt;
===Authority===&lt;br /&gt;
&lt;br /&gt;
A speaker may claim in many ways to be an authority; sometimes external checking of this is called for. Sometimes the &amp;quot;authority&amp;quot; is specious, or openly fallacious. &lt;br /&gt;
&lt;br /&gt;
In logic we refer to overextended or outright phoney cases of authority as an &amp;quot;appeal to false authority&amp;quot;.  &lt;br /&gt;
&lt;br /&gt;
===Humor===&lt;br /&gt;
&lt;br /&gt;
Humor has a great way of defusing our critical faculties. Whenever Ronald Reagen couldn't deal with facts, he'd make a joke. The most famous case was his uttering &amp;quot;There you go again!&amp;quot; to Walter Mondale during a debate. The fact that Reagen was saying this because Mondale nailed him on a fact he couldn't escape from, was lost to the audience. They preferred the humor of Reagen to the reality of Mondale. &lt;br /&gt;
&lt;br /&gt;
In logic we refer to Reagen's use of humor as &amp;quot;missing the point&amp;quot;&lt;br /&gt;
&lt;br /&gt;
===Emotional words===&lt;br /&gt;
&lt;br /&gt;
Advertisers are especially keen about the emotional qualities of certain words, and the sway they can give a speaker, just by their associations. Consider the possible power of: winner, loser, infantile, powerful, lovely, courage, freedom, radical. How are these kinds of words employed to generate a certain response in the listener? What purposes are served? A fine example would be Newt Gingrich's &amp;quot;GOPAC&amp;quot; an organization that existed to positively define conservative values and negatively define liberal values. One should ask: If conservative values are clearly superior to liberal values, why would conservative need to create an organization that purposely tried to redefine liberal values with negative words? Is this not a implicit admission from conservatives that both liberal and conservative values are in many way, on an equal par, and that that one must purposely attempt to create a distinction in order to devalue one of them? &lt;br /&gt;
&lt;br /&gt;
In logic we see that this appeal often commits the false &amp;quot;emotional reasoning&amp;quot;.&lt;br /&gt;
&lt;br /&gt;
===Pacing===&lt;br /&gt;
&lt;br /&gt;
How do you move a listener along to your conclusion? Certain phrases help a speaker move us from one idea to another, regardless of whether strong connection or evidence has been established. Don't let phrases like these lull your assessment of the argument: &amp;quot;Naturally...&amp;quot;; &amp;quot;Certainly then...&amp;quot;; &amp;quot;Surely...&amp;quot;; &amp;quot;Without question...&amp;quot; But we must question any of these terms, particularly when we have no proof of the validity of their appeals. In logic we see that this appeal often commits various fallacies of presumption, as well as circular logic and begging the question.&lt;br /&gt;
&lt;br /&gt;
===Questions===&lt;br /&gt;
&lt;br /&gt;
Jacobs points out 3 ways posing questions helps a persuader do her work.&lt;br /&gt;
1. A question can substitute for a request (recall the peas and spinach).&lt;br /&gt;
2. While a listener is searching for an answer, the speaker can give his own answer to the question. The listener is more likely to accept it than if it were given as an assertion.&lt;br /&gt;
3. A question can have a suggestion embedded in it. Sales people skillfully use questions to lead the listener and control the discussion. In logic we recognize that true questions are not logical arguments at all - making them the perfect tool for a rhetorician.&lt;br /&gt;
&lt;br /&gt;
===Absolutes===&lt;br /&gt;
&lt;br /&gt;
We've all heard &amp;quot;never say never&amp;quot;; any totalizing statement is likely to result in a fallacy. But words like &amp;quot;don't&amp;quot; and &amp;quot;must&amp;quot; creep in and can give a writer's statements and indisputable air. In logic we see that this appeal often commits the false dichotomy error or fallacies of presumption.&lt;br /&gt;
&lt;br /&gt;
==An overview of the technical aspects of Rhetoric - Grounds, Warrants and Conclusions==&lt;br /&gt;
&lt;br /&gt;
Rhetoric, according to Hannigan, involves the deliberate use of language in order to persuade, without providing logical proofs.&lt;br /&gt;
&lt;br /&gt;
Rhetoric can be said to be based on two methods: One of Emotionalism, or appealing to strong subjective emotional states (during which people usually don't make the best decisions, wouldn't you agree?) and the second on Aesthetics, or the concept that whatever best appeals to you is what is true. A fine proponent of this is any politician, who usually makes the claim that whatever you yourself desire is what is best for the country. Sounds ridiculous? Well, why do Republicans claim that Tax cuts are the solution to every problem while liberals believe a loosening of restrictions is always what is needed? Because they are playing to the aesthetic desires of their constituents!  &lt;br /&gt;
&lt;br /&gt;
Now, these emotional and aesthetic rhetorical statements contain 3 principal components: grounds, warrants and conclusions. Let's go over them.&lt;br /&gt;
&lt;br /&gt;
Grounds are the data furnished by the speaker to support his cause. This includes:&lt;br /&gt;
&lt;br /&gt;
Persuasive definitions: (Slanted definitions i.e. a person against abortion can be called either a &amp;quot;pro lifer&amp;quot; OR &amp;quot;anti choice&amp;quot; depending upon which side is referring to him or her.)&lt;br /&gt;
&lt;br /&gt;
Unscientific statistics, (often biased, if not wholesale falsified - i.e. Ronald Reagan's use of statistics), and/or&lt;br /&gt;
&lt;br /&gt;
Case study examples - Easily identifiable victims, usually of a rare and extreme nature - i.e. Rodney King beating by L.A. police is held to be indicative of normal police/black populace interaction, or , on the other side, Ronald Reagan's use of a fictitious welfare queen (a complete lie) is held to be proof of the misuse of welfare.&lt;br /&gt;
&lt;br /&gt;
Again, case study examples are shown by psychological study to be extremely convincing, since one personal example bears more weight than a bookload of negating statistics. For proof, try telling a person afraid of air travel that jets are safer than cars. (Also, see my Social Psychology page for more...)&lt;br /&gt;
&lt;br /&gt;
One should note from this open definition, that it is entirely possible for rhetoric to include valid, logical data. Usually, however, even when this is the case, it is often used in emotional or unscientific ways, or along with a conclusion that goes much further than the valid evidence supports.&lt;br /&gt;
&lt;br /&gt;
Warrants - justifications for the speaker to demand action.&lt;br /&gt;
&lt;br /&gt;
Usually, a claim that basic rights have been violated or impinged upon. Two main modes are used:&lt;br /&gt;
&lt;br /&gt;
Rhetoric of rationality Our sense of logic must compel us to agree. It makes sense for others to agree with the speaker, since they will benefit by agreeing. This is the most valid of rhetoric, because, again, it comes closest to aping the art of logic. However, while appearing like logic, often rhetoric is tinged with emotionalism, slanted views or unobjective judgments.&lt;br /&gt;
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Rhetoric of Rectitude Our values or morality should drive us to agree. No pretense of logic is made - instead, other, more important drives should motivate us, that go beyond logic. Hmmmm...&lt;br /&gt;
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Within these two basic modes, stereotypes are called upon, called rhetorical idioms:&lt;br /&gt;
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===Rhetorical Idioms===&lt;br /&gt;
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These are schemas or groups of cognitions that one stereotypically has about certain areas of moral significance:&lt;br /&gt;
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Rhetoric of loss: We are losing our innocence, our ability to enjoy nature&lt;br /&gt;
Rhetoric of unreason: we are being manipulated by a conspiracy - that somehow avoids are detection - but this is just further proof of its insidiousness! (Hey, if we could detect it, then it wouldn't be a conspiracy, right?)&lt;br /&gt;
Rhetoric of calamity: Favorite of religion - Deteriorism - the world is falling to pieces and judgment is at hand, therefore, we should change this (but, if it is preordained, can you change it? Or, even, should you??)&lt;br /&gt;
Rhetoric of entitlement: We have the RIGHT to kick the foreigners out of our country, etc. I haven't made a nazi reference in a few paragraphs, so I will note that our favorite Fuhrer, Adolf Hitler, used this technique, to justify his actions towards the Jews.&lt;br /&gt;
Rhetoric of endangerment: We must build 50,000 nuclear bombs, or the soviets will be feeding us borsch by June. And borsch sucks!&lt;br /&gt;
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Rhetorical motifs: These methods all use recurrent metaphors - with an unbelievable persuasive power to change others minds, regardless of the reality of the situation. Examples include the claim that aids is a plague, or that the hole in the ozone is a ticking time bomb, or that we are suffering under a worldwide population explosion. They appeal to all facets of rhetoric, from emotional appeal, to moral to logic. The sad truth is that all of us have swallowed more than a few of them whole, without any critical examination!&lt;br /&gt;
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(Example: - There is no ozone hole - a recolored infrared reading of ozone leaves the THINNING LAYER of ozone clear, making it look to non professionals that no ozone exists over the arctic circle. Aids is not a plague, its a sexually transmitted disease (also, through blood transfusions) and it has hardly killed off 1/2 of the worlds population like the true plagues did, and lastly, the population in Europe is decreasing, and leveling off in America - its only in 3rd world nations where the growth is still quite high (and even there, the population increase comes from longer longevity, not increasing birthrate.) None of this is intended to say these are not problems, its only intended to show that rhetoric causes overstated misperceptions in the cause of rectifying what the speakers honestly feel are horrible problems.&lt;br /&gt;
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Conclusions What action is needed to solve this problem. Usually this is simply stated as just agree/vote with/for us, and we will do the job...&lt;br /&gt;
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How to further delineate Rhetoric from logic - look for &amp;quot;Intent signals&amp;quot;&lt;br /&gt;
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I've certainly provided you with much already that stresses the differences between logic and rhetoric, but there is yet another indicator. There are things to look for in persuasive language that reveal putative self-serving motivations. Self-interest is fine, but too much of it, especially in the apparent pursuit of helping others, should cause us to question the integrity of the speaker. We call statements that reveal an abundance of self interest &amp;quot;intent signals&amp;quot; - i.e. what someone's real intent may be. Whether the presence of any of these in writing is cause for rejection requires analysis; their presence should call up further examination.&lt;br /&gt;
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Look for the following themes...&lt;br /&gt;
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Us vs. Them&lt;br /&gt;
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Does the speaker see two &amp;quot;sides,&amp;quot; with the other side being in some way inferior or denigrated? This happens all the time in environmental discourse, and often tends to cloud the real issues, and impede useful analysis. Many techniques of propaganda employ this technique: name calling, touting how great it is to &amp;quot;belong,&amp;quot; using one-sided testimonials of famous people, simplifying issues for slogans, emphasizing being on the right side of the competition.&lt;br /&gt;
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Supremacy&lt;br /&gt;
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Although there is nothing wrong with asserting superiority, it can suggest a need that is stronger than the desire to give a sound argument.&lt;br /&gt;
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Absolute Certainty&lt;br /&gt;
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Science doesn't provide it; scholarly research doesn't. Mathematics has it, but only within its self-defined deductive systems. When someone asserts they know something with absolute certainty, it can really only be based on self-evidence, faith, or mythology.&lt;br /&gt;
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Righteous indignation&lt;br /&gt;
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To quote Jacobs from his text On Rhetoric (1994, p. 74):&lt;br /&gt;
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    When someone is so full of guiltless virtue and vengeance because of &amp;quot;unjust treatment,&amp;quot; his information is likely to be biased and inaccurate. Ultimately, this could hurt a worthy cause. Admittedly, what is truth and what is worthy are difficult things to know. But if this is not appreciated by a persuader, it could indicate he has taken an easy path to his position. It shows he may not have carefully analyzed his assertions. It is not likely he has open-mindedly compared his ideas to other viewpoints. The listener should thus question his information. &lt;br /&gt;
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==Toulmin's Model of Argumentation==&lt;br /&gt;
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===Backing=== The element in the Toulmin model of argumentation that justifies believing the warrant.&lt;br /&gt;
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===Claim=== The element in the Toulmin model of argumentation that is the proposition the arguer supports.&lt;br /&gt;
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===Data=== Another name for '''grounds''' in the Toulmin model of argumentation&lt;br /&gt;
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===Fields of argument=== Subject related communities of arguers with argumentative &amp;quot;rules&amp;quot; specific to each community.&lt;br /&gt;
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===Grounds=== The element in the Toulmin model of argumentation that is the evidence used to support the claim&lt;br /&gt;
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===Modal qualifier=== Another name for the qualifier in the Toulmin model of argumentation.&lt;br /&gt;
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===Possible rebuttal=== The element in the Toulmin model of argumentation that is a statement indicating under what circumstances the claim may not be true.&lt;br /&gt;
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===Qualifier=== The element in the Toulmin model of argumentation that is any term or phrase that indicates the strength of the claim.&lt;br /&gt;
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===Verifiers=== The element added to the Toulmin model of argumentation that provides justification for believing the grounds.&lt;br /&gt;
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===Warrant=== The element in the Toulmin model of argumentation that explains why the grounds legitimately support the claim.&lt;br /&gt;
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==References==&lt;br /&gt;
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Hannigan, J. A. (1997) Environmental Sociology&lt;br /&gt;
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Verlinden, J. Retrieved from the World Wide Web on June 19, 2007.  Argumentation and Critical Thinking Tutorial.&lt;br /&gt;
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http://www.humboldt.edu/~act/HTML/tests/Toulmin/review.html&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:06:03 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Rhetoric</comments>		</item>
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			<title>Reductio ad Absurdum</title>
			<link>http://72.14.177.54/logic/Reductio_ad_Absurdum</link>
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&lt;div&gt;'''Reductio ad absurdum''' (Latin for ''reduction to the absurd'') also known as ''proof by contradiction'', is a type of logical argument where one assumes a claim for the sake of argument, derives an absurd or ridiculous outcome, and then concludes that the original assumption must have been wrong as it led to an absurd result. It makes use of the [[Law of Non Contradiction]] - a statement cannot be both true and false. In some cases it may also make use of the [[Law of the Excluded Middle]]  - a statement must be either true or false. The first documented uses of the argument are found in the writings of [[Aristotle]].&lt;br /&gt;
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In [[Formal and Informal Logic|Formal Logic]], ''reductio ad absurdum'' is used when a formal contradiction can be derived from a premise, allowing one to conclude that the premise is false. If a contradiction is derived from a set of premises, this shows that at least one of the premises is false, but other means must be used to determine which one.&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:03:00 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Reductio_ad_Absurdum</comments>		</item>
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			<title>Conclusion and Adieu</title>
			<link>http://72.14.177.54/logic/Conclusion_and_Adieu</link>
			<description>&lt;p&gt;Admin:&amp;#32;&lt;/p&gt;
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&lt;div&gt;I hope you have enjoyed this encounter as much as I have. If you have a need for further assistance, please feel free to contact Christopher Smith at hanniballecturer@gmail.com. Otherwise, I will assume that you have understood and benefited from this page. It is my humble hope that a few will learn from this page, and make the world a tad bit more... logical.&lt;br /&gt;
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 http://www.candleinthedark.com/drsmith_peaceful.jpg&lt;br /&gt;
Adieu&lt;br /&gt;
[[Logic]]&lt;/div&gt;</description>
			<pubDate>Mon, 18 Jun 2007 22:02:10 GMT</pubDate>			<dc:creator>Admin</dc:creator>			<comments>http://72.14.177.54/logic/Talk:Conclusion_and_Adieu</comments>		</item>
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