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Questions tagged [logic]

For questions about logic, whether it concerns syllogistic logic, mathematical logic or the nature of logic itself.

171 questions with no upvoted or accepted answers
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What is the difference between the resolution rule and the elimination in natural deduction?

I understand that elimination is: p v q ¬q then p and resolution is: q1 v q2 v q3...qn ¬q1 v q2 v q3...qn then q2 v q3...qn I see no difference, but my teacher is telling us don't use the ...
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Why do there exist “logical fallacies” that are not really consistent logical fallacies?

Why do there exist "logical fallacies" that are not really consistent logical fallacies? By logical fallacy, consider e.g. ad hominem. By consistent logical fallacy I refer to a type of logical ...
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3answers
99 views

Multiple connectives using atomic sentences?

Can you use multiple connectives in atomic sentences? For example, consider the following transcription guide: A. The New England Patriots are the best team in the NFL. B. The New England Patriots ...
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108 views

Has there been any philosophical guidance regarding when to use logic vs empirical testing?

One obvious disadvantage of testing a given claim with scientific constraints is that one may never know the number of possible constraints to try, in which combinations, and in which order to modify ...
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70 views

How might I notate that an entity either cannot have a quality or has all of it?

I have two friends, Charles and Louis. I want to state that given one of the following conditions then Charles and Louis are identical: Charles does nothing. Louis does nothing. Charles does ...
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76 views

What are the Limitations and Vulnerabilities of Objectivity Biases?

How reliable is a "Logic / Objectivity" Bias when it comes to reasoning? Or, What are the potential limitations or vulnerabilities of relying solely on these bases of reasoning? Note 1: "Objectivity"...
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134 views

In the context of debate centred on a statement, how to validate arguments given to confirm or disconfirm that statement in a logical manner?

Let's say we have the following statement to serve as a starting point around which a debate can be centerd. Man is immortal Someone could say that man is mortal according to accepted scientific ...
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128 views

Concerning the integrity of some logical syllogisms on moral subjectivism and ice-cream

I understand moral subjectivism to be the meta-ethical idea that all moral statements are merely expressions of the individual and thus that there are no moral statements that are implicitly (...
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60 views

Liar paradox from a different view/resolved?

Informally, the statement T: T: "this statement is not both true and not true" a) T is not true if and only if it is both true and not true b) T is true if and only if it is not both true and not ...
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86 views

What irreducible functions constitute thinking?

Because all new knowledge, to be not illogical, must obey logic i.e. every thinking step must be consistent with rules of logic; so can we write an effective procedure/algorithm which may be followed ...
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Fitch Proof Final Step

I've been able to get this far, but I don't know how to finish it off. This setup was given to us as an something that can be proved as a proof without premises in the form ((P → R) ∨ (Q → R)) → ((P ∧ ...
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28 views

Existential Elimination in Fitch (Barber of Seville)

To be clear, I'm just struggling to understand why Fitch won't let me use EE. From other examples I've seen, I've set it up correctly for EE. I've also tried using BotE and EE on the desired sentence, ...
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137 views

Is there an existing, published philosophy of mathematics that was designed to avow or declare all of the following four points of view?

Just as medicine is about human health, and astronomy is about the universe beyond the Earth's atmosphere, with the defining nature of medicine not white coats or stethoscopes, and the defining nature ...
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38 views

Is this logic correct?

I just can’t work out if the logic is correct. Please completely and absolutely ignore the content, it is just the logic and the form of the argument I am trying to validate. P1. Unless we are ...
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80 views

Honestly have no Idea how to prove A v ¬¬B from A v B (LPL Q. 6.18)

Premise A v B Goal A v ¬¬B Please help. It seems so self evident but I don't know how to get there.
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A question about possibility

If A, then B ~ A So, possible that B Valid or not? My take: Not valid. Reason: Valid means if all the premises are true, the conclusion must be true That means adding new information should not ...
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52 views

Deterrent effect of nuclear weapons in comparison with carrying Firearms?

Would it be feasible to to compare the deterrent effect of nuclear weapons between nuclear armed countries (if such exist), with the deterrent effect of a majority of citizen carrying firearms, inside ...
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182 views

Can something end which never began?

I was thinking that if life is infinite then it has no meaning. But if life began then the meaning of life must be for it to end. The meaning is in the future and since the last thing that will ...
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739 views

Can a sentence without a truth value be true?

I was doing some very, super, light reading on self reference. It seems to me that the statement nothing that I say is true both: cannot be understood with the T-schema; is self referential. - ...
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58 views

Does a logician need to memorize all binary logical connectives truth tables, equivalences, and properties?

Pretty much what is contained in these pages: https://en.wikipedia.org/wiki/Logical_connective https://en.wikipedia.org/wiki/Truth_function I feel like having all this info burned into my head and ...
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1answer
248 views

What is the difference between class and concept?

What is the difference between class and concept? − I am not sure whether, for instance, “chair” is typically a class or rather a concept, or both. I would say that it is only a class, though it is ...