Philosophy Stack Exchange
Philosophy Stack Exchange

Questions tagged [tautology]

26 questions
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Why is it wrong to answer a question with a tautology? Isn't "2+2" correct when answering 'What is "2+2"'?

Many times in class, we are asked to answer, "What is 2+2?" or "What is the derivative of the function x?". It would not be the intended answer to write "2+2" or "The derivative of the function x". But, why not? A tautology is technically a correct…
user107952
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Difference between Tautology and Circular Reasoning

Often it is considered that a tautology is the same as a circular reasoning. However, in the Wikipedia entry of Tautology (language), it mentioned that circular reasoning and tautology are different. Can someone elaborate how they are different? I…
shivams
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Does the phrase "vacuous tautology" have specific meaning?

I just came across a use of the phrase "vacuous tautology" used in a piece of writing. Now, based on my understanding, by definition a tautology has no content and is therefore always vacuous. This would make the use of the word vacuous in "vacuous…
yamad
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Why does logic emphasize tautologies rather than contradictions?

Why does logic emphasize tautologies rather than contradictions? I think the answer is something like the following: We can't cover all cases by contradictions. For example: if I have to prove that p implies q, then I can prove it by contradiction,…
TLE
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Making 'sense' of Wittgenstein's senselessness / nonsense distinction in the Tractatus

For this question I'm just considering Wittgenstein's theory at the time of the Tractatus. As far as I know, for Wittgenstein: Meaning - The object denoted by a word (i.e. referent). Sense - The conditions under which a sentence can be verified or…
M. Guillaume
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Counterexamples to Occam's Razor and tautology

I read here and here that, strictly speaking, there are no counterexamples to Occam's razor, because the latter implies no need for pluralism when unnecessary, which is to be understood as "for the theory to be correct". For example, if a simple…
luchonacho
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How do you prove that this is a tautology?

((p->q) and (r->s) and (p or r)) -> (q or s) How would you prove that this is a tautology? Using natural deduction? My attempt on this question is the following. Since a tautology means W entails by empty premise and W is something of A->B, where A…
Tom chan
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What is the relation between a priori and tautologies?

I have just started learning Epistemology. I am not sure about the relation between a priori and tautologies. My textbook has given definitions for a priori and tautology. A priori: knowledge which is dependent on the meaning of words, not sense…
Heidi Zhang
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Is "Unreasonable Effectiveness of Mathematics in the Natural Sciences" a tautology?

According to Gelfand, "Eugene Wigner wrote a famous essay on the unreasonable effectiveness of mathematics in natural sciences. He meant physics, of course. There is only one thing which is more unreasonable than the unreasonable effectiveness of…
Michael
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What is the difference between a logical truth and a tautology?

Some papers I read seem to be referring to a distinction between logical truths and tautologies. At first I thought something was wrong since I thought they are the same by definition. I checked the Wikipedia article, "Logical truth", and I noticed…
peticrust
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How can a tautology not be necessarily true?

My logic/philosophy exercises include the following statement: "Every tautology is knowable a priori but not every tautology is necessarily true." I'm bamboozled. How can a tautology not be necessarily true? If it's a tautology, then it's true in…
Brendan Hill
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In the usual modal logics, are there tautologies of the form ◊¬X or ¬☐X?

And not when, "Possibly not X," or, "Not necessarily X," are implied by, "Impossibly X," already. But so is it possible to have a tautology be a statement of mere contingency? I suppose the statement itself is not contingent, i.e. if it is…
user40843
2
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The Law of Identity and Emptiness

If all rational, logical, philosophical, scientific, and mathematical reasoning starts with the initial axiom that 'X=X' - that is a 0 information tautology - can it be said that all ensuing rational, etc statements are therefore empty of any…
Ilya Grushevskiy
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Valid arguments as tautologies

I don't quite understand this : "As it turns out, all valid arguments can be restated as tautologies - that is, hypothetical statements in which the antecedent is the conjunction of the premises and the consequent the conclusion. In other…
Hiroki Hirayama
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Interesting non-mathematical tautologies

Are there any interesting examples of tautologies that are not mathematical? Something non-trivial like It is raining or it is not raining. I can't come up with one nor have I found any on the internet. Example: the mathematical statement of the…
Alex
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