What is Logic? (Philosophical Definition)

A definition of Logic as a field of philosophy, as well as several types of logic studied in philosophy, including second order logic, non-classical Logic, and modal logic.

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Information for this video gathered from The Stanford Encyclopedia of Philosophy, The Internet Encyclopedia of Philosophy, The Cambridge Dictionary of Philosophy, The Oxford Dictionary of Philosophy and more!

Information for this video gathered from The Stanford Encyclopedia of Philosophy, The Internet Encyclopedia of Philosophy, The Cambridge Dictionary of Philosophy, The Oxford Dictionary of Philosophy and more!
(#Logic #Modal)

[lordmurphy]

Damn, this channel deserves way more subs

[jadejewell]

You could just say, "Logic is a tool used to determine whether or not an argument can demonstrate its claim"

[Dare]

your videos are truly awesome. can I use them to help teach my logic class?

[Thomasvanlankveld]

I'd be very interested in videos on intuitionistic logic! While it is not too hard to find introductions to second order logic and set theory, I'm having a hard time finding introductory sources to intuitionistic logic. Also, since it is a more strict logic, I'd be very interested in hearing your thoughts, as a sceptic, on the problems that intuitionistic logic does and does not solve. In any case, thank you for the great videos!

[Rogersensei]

For some reason the thought of "what is being rational?" popped in my head then I searched it and it said it was based on logic. Then I asked "what is logic?" and here I am

[Nicoder]

I think you should do Second Order Logic, then Non-Classical Logic. Or the other way around. Anyway, I think that they both deserve a full series.

[jeanduplessis]

Well I will need to watch this a few times.

[r.lizarraga]

But what is the ontology of logic? Is it a platonic form or a neurological expression of the brain? How do we identify logic from non-logic?

[stayinawesum]

can u suggest some beginner level books on:
1/ overview of different kinds of logic
2/ books on specific major logic type
(pls suggest some popular ones, thank u)

[MindForgedManacle]

You're next series should be on Non-Classical Logics. :P It's a topic I enjoy studying, haha.

And maybe once you've done videos on the topics you mention in this video, you could do a video on how to pick between logics. My preferred answer (from the work of Graham Priest) is to appeal to a model of rational theory choice. :)

[frankjaeger]

Are you ever going to make videos on semantics, explaining the difference between the semantics for natural language and for formal languages?

[williamspringer]

This video is designed to keep you confused .
The science of logic was invented by Aristotle during the fourth century B.C., as a systematic method of evaluating arguments in order to determine if they are properly reasoned. In his book "The Underground History of American Education" historian John Gatto argues very persuasively that, though the science of classical logic is taught in expensive private schools in the US today, it hasn't been taught in our State controlled public schools for more than a century. There are good reasons for this. It is hard to lie to people who know how to logically evaluate an argument. Due to our schools, even the vast majority of the elderly in our population have no effective understanding of the science of logic or the art of rhetoric. •••

"Logic, therefore, as the science of thought, or the science of the process of pure reason, should be capable of being constructed a priori."
-Arthur Schopenhauer, "The Art of Controversy", (1831)
("A priori" is defined as deduced from self-evident premises.) ••••••••••

"Logic: The science that investigates the principles governing correct or reliable inference. "
-"Webster's Unabridged Encyclopedic Dictionary" ••••••••••

"Infer ... v., 1. To derive by reasoning; conclude or judge from premises or evidence ..."
-"Webster's Unabridged Encyclopedic Dictionary" ••••••••••

"For logic is the science of those principles, laws, and methods which the mind of man in its thinking must follow for the accurate and secure attainment of truth." -Celestine N. Bittle, "The Science of Correct Thinking: Logic", (1935) ••••••••••

"We suppose ourselves to posses unqualified scientific knowledge of a thing, as opposed to knowing it in the accidental way in which the sophist knows, when we think that we know the cause on which the fact depends, as the cause of that fact and of no other, and further, that the fact could not be other than it is".
-Aristotle, "Posterior Analytics" ••••••••••

"We ought in fairness to fight our case with no help beyond the bare facts: nothing, therefore, should matter except the proof of those facts."
-Aristotle, "Rhetoric" ••••••••••

"Without the presentation of solid evidence no argument can be a good one"
-Patrick Hurley, "A Concise Introduction to Logic", (1985) ••••••••••

"Fallacious reasoning is just the opposite of what can be called cogent reasoning. We reason cogently when we reason (1) validly; (2) from premises well supported by evidence; and (3) using all relevant evidence we know of. The purpose of avoiding fallacious reasoning is, of course, to increase our chances of reasoning cogently."
-Howard Kahane, "Logic and Contemporary Rhetoric", (1976), second edition ••••••••••

"The province of Logic must be restricted to that portion of our knowledge which consists of inferences from truths previously known; whether those antecedent data be general propositions, or particular observations and perceptions. Logic is not the science of Belief, but the science of Proof, or Evidence. In so far as belief professes to be founded on proof, the office of Logic is to supply a test for ascertaining whether or not the belief is well grounded."
-John Stuart Mill, "A System of Logic", (1843) •••••••••

"And if we have a right to know any Truth whatsoever, we have a right to think freely, or (according to my Definition) to use our Understandings, in endeavouring to find out the Meaning of any Proposition whatsoever, in considering the nature of the Evidence for or against it, and In judging of it according to the seeming Force or weakness of the evidence: because there is no other way to discover the Truth."
-Anthony Collins, "A Discourse of Free Thinking", (1713), taken from the first page of "Thinking to Some Purpose", by L. Susan Stebbing, (1939) ••••••••••

"Aristotle devides all conclusions into logical and dialectical, in the manner described, and then into eristical. (3) Eristic is the method by which the form of the conclusion is correct, but the premises, the material from which it is drawn, are not true, but only appear to be true. Finally (4) sophistic is the method in which the form of the conclusion is false, although it seems correct. These three last properly belong to the art of Controversial Dialectic, as they have no objective truth in view, but only the appearance of it, and pay no regard to truth itself; that is to say, they aim at victory."
-Arthur Schopenhauer, "The Art of Controversy", (1831) ••••••••••

"The fallacy of suppressed evidence is committed when an arguer ignores evidence that would tend to undermine the premises of an otherwise good argument, causing it to be unsound or uncogent. Suppressed evidence is a fallacy of presumption and is closely related to begging the question. As such, it's occurrence does not affect the relationship between premises and conclusion but rather the alleged truth of premises. The fallacy consists in passing off what are at best half-truths as if they were whole truths, thus making what is actually a defective argument appear to be good. The fallacy is especially common among arguers who have a vested interest in the situation to which the argument pertains."
-Patrick Hurley, "A Concise Introduction to Logic", (1985) ••••••••••

"A high degree of probability is often called 'practical certainty.' A reasonable man should not refrain upon acting upon a practical certainty as though it were known to be true. In England, for instance, it is customary for a judge, at the trial of a person accused of murder, to instruct the jury that an adverse verdict need not be based on the belief that the guilt of the prisoner has been ' proved ', but upon the belief that the guilt has been established ' beyond a reasonable doubt .' To be ' beyond reasonable doubt ' is to have sufficient evidence to make the proposition in question so much more likely to be true than to be false that we should be prepared to act upon the supposition of its truth. Many of our most important actions have to be performed in accordance with belief of such a kind."
-L. Susan Stebbing, "Logic in Practice", (1934) pages 98 and 99 ••••••••••

"An argument is a special kind of expression of inference, one that attempts to prove something on the basis of evidence."
-Patrick Hurley, A Concise Introduction to Logic, (1985), 2nd edition

"The statements that make up an argument are divided into one or more premises and one and only one conclusion. The premises are the statements that set forth the the evidence, and the conclusion is the statement that is claimed to follow from the evidence."
-Patrick Hurley, A Concise Introduction to Logic, (1985), 2nd edition

"A sound argument is a deductive argument that is valid and has true premises. Both conditions must be met for an argument to be sound, and if either is missing the argument is unsound. The qualification that the premises must be true means that all premises must be true. Because a valid argument is one such that if the premises are true it necessarily follows that the conclusion is true, and because a sound argument does in fact have true premises, it follows that every sound argument, by definition, will have a true conclusions as well. A sound argument, therefore, is what is meant by a "good" deductive argument in the fullest sense of the term."
-Patrick Hurley, A Concise Introduction to Logic, (1985), 2nd edition

"A cogent argument is an inductive argument that is strong and has true premises, and if either condition is missing the argument is uncogent. A cogent argument is the inductive analogue of a sound deductive argument and is what is meant by a " good" inductive argument without qualification. Because the conclusion of a cogent argument is genuinely supported by true premises, it follows that the conclusion of a cogent argument is probably true."
-Patrick Hurley, A Concise Introduction to Logic (1985), 2nd edition

[kotcgoh]

How about formal and informal logic? What’s the difference between them?

[yadisfhaddad]

So Logic is like Recursion. You have to use it to define it to use it and to define it and to use it ....

[TheRobel]

Please do more videos on Second order logic, especially pertaining to Set theory. Also do you have videos on propositional quantifier logic?

[stayinawesum]

Questions: how many and which logic does maths uses, and which one of these comes under which category of logic: deductive and inductive reasoning. And finally whats the difference between logic and reasoning

[MScienceCat]

Can it be improved? I'm bad at math + I'm bad programmer too, Idk if that was my lazy brain not learning something so long or?
Can it be improved like a skill or its just genes lie intelligence?

[Lanis-ng]

could you please suggest a good textbook, for the first order logic.

I have an access to an academic library of my university.

Help will be appreciated :)

[patriciamcgeorge]

This is the basic/same premise for Godspeak - the Conlang which basically describes the world using equations, where sentence structure comes from coding/programming with some PredCalc influences, semantics comes from Logic theory, Syllabic Structure/Views on reality comes from science and overall mechanics come from maths.

[amirehosseyni]

perfect ! This gives very good intuition to a beginner !