Questions tagged [logic]

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

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Besides notation, how does (x)ℱx differ from ℱx?

Abbreviate Bound Variable to BV, Free Variable to FV, Universal Generalisation to UG, and Universal Quantifier to UQ. Source: A Concise Introduction to Logic (12 Ed, 2014) by Patrick Hurley [p 456:...
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Is falsificationism a reliable scientific methodology?

Initially it seemed to me that falsificationism is a reliable scientific methodology for disregarding hypotheses/theories. Upon some thinking, however, I conclude that it is not. Below I explain why. ...
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A question about taxonomy terms' usage [closed]

I am working on a paper in English and have stuck at taxonomy terms' usage. It is accepted that 'scientific disciplines divide the particulars they study into kinds'. But there are also taxonomy ...
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Conditional statements truth table [duplicate]

Possible Duplicate: How can we reason about “if P then Q” or “P only if Q” statements in propositional logic? I have read in quite a few books that the proposition 'p->q' can be read as either '...
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I search an example of an ad hominem argument, which is not simultaneously an argument from analogy

Incidentally I found an old copy from a book, with this claim: “Hence most ad hominem criticisms are really forms of the argument from analogy” (Douglas Walton, Ad Hominem Arguments, Tuscaloosa, The ...
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A Critcism of the Ontological Argument for God

Allow me to present the argument: (1) By definition God is that being which possesses every perfection. (2) Existence is a perfection. (3) Therefore, God exists. Whether you agree is not important,...
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Descartes's *Cogito* from a modern, rigorous perspective

In Descartes's Meditations, in order to establish a firm foundation upon which he could build a framework to determine philosophical and material truths, he begins by removing all of his then-current ...
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What exactly does 'Some' mean in Logic?

If the argument (1) Some dogs are carnivores. (2) Some dogs are mortal. (c) Some dogs that are carnivores are mortal. is given, do those 'some dogs' refer to two different groups (dogs might or ...
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Before (dis)proof, how can you determine the conclusion of given collection of long complicated premises?

Source: p 287, Sweet Reason: A Field Guide to Modern Logic (2010 2 ed) by Henle, Garfield, Tymoczko. [1.] Predicate is the reason we started on deductions. In Sentential, remember, we can verify ...
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What does the statement “Xs exist” really mean?

If someone were to claim: Xs exist. what do they actually mean? Do they mean: At least one X exists. or At least two Xs exist. In other words, does the phrase "Unicorns exist" mean "at least ...
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How to use “some” and “not all” in logic?

As asked here about the difference between "some" and "not all". I'm looking for a practical example in real world where these two can be applied. Do we have a situation where we can use either of ...
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362 views

For Universal Instantiation of a Variable, besides notation, does (x)ℱx differ from ℱy?

Source: A Concise Introduction to Logic (12 Ed, 2014) by Patrick Hurley [p 464:] Since, however, the first eight of these rules [of Inference] [hereafter ROI] are applicable only to whole lines ...
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At which point is an insult no longer ad hominem?

During an argument with some people, I come to the conclusion that they are either stupid, ignorant or liars. Let's imagine that we have 2 guys discussing what color they should be painting a room. ...
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Fitch Arrow Proofs [closed]

Using the FITCH program and the FITCH derivation rules you should make a proof or derivation of C10 from P5 through P11. P5: ∀x∀y(StrongPref(x,y)→ ¬StrongPref(y,x)) P6: ∀x∀y∀z((StrongPref(x,y)∧...