Questions tagged [logic]

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

Filter by
Sorted by
Tagged with
1
vote
1answer
41 views

What type of fallacy does the phrase “I don't live to eat, I eat to live” fall into?

I would say it's a non sequitur but I believe there's a narrower term for it.
2
votes
0answers
49 views

Why did Hilary Putnam change of opinion towards Quantum Logic?

Hilary Putnam is known for having proposed a radical change in our thinking about the physical universe: He proposed that the universe was fundamentally based on Quantum Logic, and not in Classical ...
1
vote
1answer
40 views

In what contexts or disciplines does “One may assume X” imply “One may ignore the possibility of any statement contrary to X being true”?

In computer programming, it has become fashionable for compilers (processors of computer language) to apply the following form of reasoning: A language standard would permit a compiler to assume that ...
1
vote
1answer
120 views

Comparisons between two notions of existence

I have the following, rather naive question: To what extent can the a priori existence of mathematical objects be reasonably compared with the seemingly a posteriori existence of objects established ...
-3
votes
0answers
119 views

Did any logician object to the idea that if two contingent propositions are true, then they imply one another?

Both the following sentences are true: On January 22, 2020, the earth is orbiting the sun. On January 21, 2020, Trump was the 45th president of the United States of America. So did any ...
0
votes
1answer
103 views

Is a model of inference needed for reasoning?

In logic we can't make any deductions without rules of inference, predicates, and formulas. In probability/statistic we can't make any inferences without assuming some probabilistic model which might ...
0
votes
1answer
36 views

How do I prove :((A ⊃ B) ⊃ C) ⊃ (B ⊃ C)?

How do I prove, :((A ⊃ B) ⊃ C) ⊃ (B ⊃ C), using symbolic logic derivations where ⊃ represents a conditional i.e. A ⊃ B = A implies B? The first line of my derivations is the assumption, (A ⊃ B) ⊃ C)....
0
votes
0answers
45 views

2+2=4 why is this a deductive logical inference? [closed]

I googled a a deductive logical inference https://www.google.com/search?client=firefox-b-d&q=a+deductive+logical+inference%3F and couldn't understand a thing. But I presume it's because if 2+2 ...
3
votes
2answers
70 views

In non-platonism, can undecidable statements have truth value?

Most sources I can find about Gödel's incompleteness theorems summarize the result as "there exist true arithmetical statements that have no proof." It seems coherent to say that there exist ...
3
votes
3answers
168 views

From Ignorant to Researcher in Modal Logic

I am a student in a French university in pure mathematics. I recently came across modal logic and more particularly doxastic logic. But, the only masters of logic offered are reserved for students of ...
1
vote
2answers
64 views

Does a formal fallacy definition for “X has not happened (with potential time constraint Y), so Z will not happen (now or in near future)” exist?

Does there exist a formal definition for (what I would say is) a logically fallacy that would fit to the following structure of statements: "X has not happened (with potential time constraint Y), so ...
2
votes
3answers
105 views

Before Gödel, was undecidability of axiomatic systems an issue at all?

Before Gödel, was the issue raised that there may be undecidable statements within axiomatic systems of thought? Gödel managed to answer affirmatively by proving that the assumption of the ...
1
vote
1answer
17 views

In Quine's ontology, why does a 'recognition' of something lead to ontological commitment while a 'feeling' does not?

We are discussing Quine's On What There Is in a metaphysics class I am in. I felt like I understood what he meant, that if something has to be predicated for in a sentence, we are ontologically ...
2
votes
0answers
48 views

Is there a logical argument for the limit of knowledge?

It is justifiable to assert that certain knowledge could not be disseminated without the invention of writing. One could say that humanity needed the knowledge of writing before further knowledge ...
7
votes
2answers
150 views

How do proofs about logic fit into a logical framework?

I'm learning logic from Michael O'Leary's A First Course in Mathematical Logic and Set Theory. In chapter 1 he carefully explains the meaning of logical implication (p ⊨ q), logical inference (p ⟹ q), ...
2
votes
2answers
80 views

Proving A ⊨ B iff ⊨A → B

Let A and B represent arbitrary formulas. Also let 1 ≡ True and 0 ≡ False Prove that A ⊨ B iff ⊨A → B For my proof, I break down the biconditional into two conditionals and prove each conditional. ...
0
votes
0answers
56 views

About Wigner's view on the relation between mathematics and physics?

Physicist Eugene Wigner argued that the enormous usefulness of mathematics in the natural sciences is something bordering on the mysterious and that there is no rational explanation for it ...
2
votes
1answer
112 views

Did Stephen Hawking think that logic is contingent on physics?

According to this book*: Extrasensory Perception: Support, Skepticism, and Science, it says that Stephen Hawking thought that logic was contingent on physics, i.e that logic depends on the physics of ...
10
votes
5answers
3k views

Name for this Logical Fallacy

Suppose there is a non-empty subset A of U. Let A' denote the complement of A in U. What is the name of this logical fallacy? X is true for A therefore not X is true for­­­­­­­­­­­­­­­­­­ A' ...
1
vote
1answer
42 views

Does anyone have an example where a sufficient condition comes first?

Example: Sufficient Condition of A+ MUST MEAN Necessary Condition of Studying occured Temporally speaking, either condition can occur first, or the two conditions can occur at the same time. In our ...
0
votes
0answers
32 views

logical atomism explanation with examples

I read a bit of logical atomism by Russel but would appreciate if someone explains with examples of what is meant by it. For example it says:" According to logical atomism, all truths are ultimately ...
0
votes
2answers
60 views

Is there a term for such a logical fallacy?

I'm wondering if there is a terminology for the following logical fallacy: Joe: Statement "X" must be true because it is clearly laid out as such in mutually reliable source "Y". Sam: Joe, the ...
3
votes
2answers
78 views

Term for evidence that isn't understood

Imagine someone asks how you can believe that whales evolved from land animals. You tell them about "missing link" fossils that chronicle whales' evolutionary journey. This is solid evidence - to ...
0
votes
1answer
44 views

Learning Logic, A Pathway

I would like to devote a greater amount of time to further learning logic. I have experience with mathematical proofs and thus have an understanding of logic to the degree necessary for proofs. I ...
0
votes
1answer
78 views

Is there a logical fallacy to identity politics?

My understanding of Identity Politics goes as follows: A is a member of/identifies with group X B is not a member of/does not identify with group X A frames challenge S in terms of X Because B doesn’...
5
votes
4answers
159 views

Where did Suárez say the principle of non-contradiction does not apply to the Trinity?

Fr. Réginald Garrigou-Lagrange, O.P., says, in Le Sens du Mystère et le Clair-Obscur Intellectuel: Nature et Surnaturel p. 128 fn. 1 (Engl. transl. p. 142 fn. 41): St. Thomas never would have ...
0
votes
1answer
54 views

What is the meaning of Principle C'' in Hartry Field's 'Science Without Numbers'?

For Field, the following is 'perfectly obvious', but I would like confirmation that I understand it completely. Let A be a nominalistically statable assertion. Let A* be the assertion that results by ...
0
votes
7answers
170 views

Why do people use the material implicaton over alternatives?

It isn't because it works. There are numerous alternative, fully-functioning implication systems. If people have a problem with conditionals with false antecedents, and with true consequents, always ...
0
votes
0answers
56 views

Is there a semantically complete system of direct-method deductive logic?

Does anybody know of a system of direct-method deductive (propositional) logic, in other words, a system that does not require (or even incorporate) conditional (and indirect) proof method(s) and that ...
1
vote
0answers
37 views

What is an enumerative definition?

W. Kent Wilson in his book argues for developing an enumerative definition of concepts. An enumerative definition formulates its meaning by enumerating the objects or phenomena that fall under the ...
0
votes
0answers
35 views

Why is the material conditional a thing? [duplicate]

If people have a problem with conditionals with false antecedents and with true consequents always being true, why not just change it according to what is found to be more intuitive? Regarding ...
1
vote
3answers
58 views

What reasons do I have to believe that ~p->~q and pV~q are equivalent?

I understand the reasoning for why pVq implies ~p->q, but not the converse. What reasons are there to believe ~p->~q implies pV~q, other than to make the whole material implication system neat?
1
vote
0answers
25 views

Does denying the Limit Assumption in counterfactual logic lead to contradiction?

According to the similarity semantics for counterfactuals, a counterfactual A > C is true iff on the most similar class of worlds to the actual world (or any given world the counterfactual's truth ...
4
votes
1answer
91 views

Can/Do there exist any quantifiers other than “there exists” and “for all”?

I'm curious about why there are only the two logical quantifiers there exists and for all. Intuition and human language support the idea that these quantifiers make sense, but otherwise it seems ...
8
votes
2answers
1k views

What did Gödel mean by “positive property” in his ontological argument?

In his ontological proof, Gödel states (Axiom 1) If a property is positive, then its negation is not positive. What does he meant by this term? I have come across authors who replace this notion ...
0
votes
1answer
286 views

Is God's existence either impossible or necessary?

This is meant as a supplement to a modal ontological argument to show that God's existence is either logically impossible or necessary. Am I committing a fallacy or a logical error of some kind or ...
0
votes
1answer
143 views

Wittgenstein and “linguistic trap”

In a book on philosophy I've lost by now I encounter an argument about "linguistic trap" idea attributed to Wittgenstein, that is, such a trap is supposed to be "taking linguistic convention or ...
0
votes
0answers
113 views

Bibliography about non-mathematical applications of logic:

I have been recently playing with modal and temporal modal logics in the context of "organisms" (mostly after some study of entelechy in Aristotle and relatedly, some ideas of current biology). I have ...
0
votes
0answers
27 views

When thinning on the right how is it correct that the number of formulae on the right can be increased from zero to one?

I understood there being no formulae to the right of the turnstile as meaning that the formulae on the left was inconsistent. However, my textbook writes that there is a special case of thinning on ...
0
votes
0answers
52 views

Is this statement self-defeating?

Would the statement "I don't want to talk about cars" be a self-refuting statement in that the statement itself "talks" about cars?
4
votes
2answers
509 views

How to show (in a hand waving manner) that the Godel sentence is true

I have been reading Graham Priest's The Logic of Paradox, and there is a section where he tried to show that our informal proof argument (in Priest's terminology, naive proof procedure) is more ...
0
votes
0answers
17 views

Can these selfreferential statements be rewritten as such?

This statement is a paradox = this statement is both true and false this statement is a hypodox = this statement is either true or false this statement is a contradiction/always false = this ...
1
vote
2answers
164 views

always false vs necessarily false , is it the same?

according to the basic tenets of classical propositional logic, contradictions are 'always false' tautologies 'always true'. When it is extended to modal logic we have the notions of 'necessarily ...
1
vote
1answer
81 views

Kant claimed that 7+5=12 is a synthetic proposition; is this not obvious?

Whenever anyone claims that 7+5=12 is an analytic proposition, they are overlooking one important detail. What is that? Charles M. Saunders
2
votes
3answers
99 views

If cause C has the mutually exclusive effects Y and Z, then is causality held? Why?

Imagine there is a cause but several effects. Of course determinism is not held, but my question is about causality. If cause C has two mutually exclusive effects Y and Z, then at each given time ...
0
votes
0answers
48 views

Logical Notation in Anscombe's “Causality and Extensionality”

In "Causality and Extensionality," Anscombe writes thus: Our argument uses the description of a class—say x̂(Gx · p), assuming G to be a respectable class-forming predicate. Let G be such that x̂(Gx) ...
1
vote
2answers
152 views

Heraclitean, Parmenides, and Aristotelian change? Is there an alternative?

Dear philosophy stack exchange, I've been considering of late the problem of change as presented by Heraclities and Parmenides as well as the supposed solution to the problem by Aristotle himself. I ...
4
votes
2answers
123 views

Question about conditionalization and probability

I am working on a problem set and I am not sure if I am heading in the right direction. The scenario: "Suppose three identical boxes are presented to you, and you are told that one box contains two ...
4
votes
2answers
44 views

Question about anchoring and adjustment (Tversky and Kahneman) and why anchoring often yields correct judgments

I am working on a problem set and I am having some difficulty wrapping my head around a concept introduced by Tversky and Kahneman. My problem set asks the question "Why does anchoring nevertheless ...
1
vote
2answers
583 views

If other versions of us existed in a multiverse, would we be morally responsible for the actions of these alternate versions of us? [closed]

Hypothetically, if we lived in a multiverse which contained an infinite number of identical versions of each of us containing our respective memories and experiences, with the exception of key ...