# Questions tagged [logic]

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

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### Are the “laws” of deductive logic empirically verifiable?

"Is Logic Empirical?" strongly suggests a question that I would like very much to get a handle on. That phrase is a title of an article by Hilary Putnam, and, according to synopses/reviews, the ...
277 views

### How do disjunctive antecedents work in Marc Lange's stability concept of laws of nature?

I'm an ecology student who's dabbling into philosophy of science. I'm currently writing a term paper on laws of nature (with a focus on ecology as a special science) and try to wrap my mind around ...
63 views

### The enunciation clause (Lyotard & Levinas)

As kind of introductory remark, let me state that I'm not academically-trained in philosophy, so my apologies if this comes up as a rather simple question. I was reading Logique de Levinas by JF ...
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### Which problem is Russell focusing on while providing a solution, in his introduction to the Tractatus?

In the final part of his introduction to the Tractatus Logico-philosophicus, Russell provides a possible solution to the problem of the impossibility of self-reference of logic: There is one ...
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### Conditional logic - how to apply a conditional with complex antecedent in tableaux?

I'm referring to the conditional logic of C+ as described Graham Priest in "An introduction to non-classical logic" chapter 5, where the strict conditional is enhanced with ceteris paribus, and a ...
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### Is Herbrand semantics a kind of term formalism?

Michael Genesereth and Eric Kao describe Herbrand semantics as follows: Herbrand semantics is an alternative semantics for First Order Logic based on truth assignments for ground sentences rather ...
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### Formal logic to describe causation?

I'm looking for any formal work that has been done on describing causation the way people understand it. I am not looking for logical implication, more a way to talk about "Why?" questions. Basically, ...
130 views

### Are Wittgenstein's propositions analytic or synthetic?

Wittgenstein provides a logical analysis of propositions in the Tractatus. Does he there admit the Kantian distinctions between analytic/synthetic and a priori/a posteriori divisions; or does his ...
397 views

### Is Tarski's derivation of the Liar paradox valid?

First a link to his derivation: http://www.jfsowa.com/logic/tarski.htm Its a famous essay so you really should read all of it but at the moment its enough if you read section 7 where Tarski derives ...
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### Given the principle of innocence, how shall we explain logic's usefulness?

I have been reading Florian Steinberger's dissertation (Harmony and logical inferentialism) and I come across the following on p60: ...two fundamental assumptions (the other one being the principle ...
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### Modal essence of potentiality

What is the modal essence of Aristotelian potentiality? Why and how potentiality seems to be inherently modal?
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### De Re, Counterfactuals, and rigidity

This is going to come off as vague or obscure; but, I hope the idea is performatively expressed: Two questions: Do you think that Kripke would argue that the impossibility of de re counterfactuals ...
63 views

### Grice: Comparing Natural Meaning, Non-Natural Meaning, Conventional Implicature and Generalized Conversational Implicature

I am currently reading "Meaning" and "Logic and Conversation" by Paul Grice. I find it a little difficult to differentiate clearly between his concepts "natural meaning", "non-natural meaning", "...
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### What are the consequences of rejecting identity of indiscernibles

What kind of system are we in if we explicitly take its negation as an axiom? Here's the identity of indiscernibles. (1) ( ∀P.P(x)↔P(y) ) → x = y Here it is written in prenex normal form (2) ∀x∀y.∃...
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### Does Tegmark himself include paraconsistent mathematical structures in his mathematical multiverse hypothesis?

Tegmark postulates in his hypothesis that all possible mathematical structures would exist. But does he include also possible mathematical structures described by other types of logic like ...
56 views

### Are there degrees of rationality/plausibility to assumptions?

There are many kinds of premises, in every possible field. I'll limit this question to metaphysics, although it can definitely be applied to each and every scientific/philosophical study. For example,...
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### What to read for an introduction on the epistemology of logic?

I would like to read about the epistemology of logic, preferably at a undergraduate level (not being a philosopher myself). What (text)book should I read for a good introduction on these topics? The ...
254 views

### Could we develop a notion of conceivability that would allow us to imagine impossible/inconsistent/illogical things?

There are things that we cannot imagine because they are impossible (like a solution to Russell's set theory, since it is impossible to reach that solution because it is illogical.) Some months ago, ...
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### Why isn't humanistic logic taught in schools any more?

Specifically, I'm curious about the loci or categories that Agricola and later Ramus used extensively. Were they found to be problematic at a later time? If not, why not use them? They're so helpful ...
79 views

### Is a Thomist possible modal proposition a non-judicative proposition?

According to Thomist philosophy and logic, is a possible modal proposition (either divisive or compound) a non-judicative proposition? It would seem to me that the other three modal propositions (...
361 views

### What are some of the best books for a robust introduction to Logic and Critical Thinking?

As the question states: What are some of the best books for a robust introduction to Logic and Critical Thinking? My background: I'm 24, graduating with two degrees in Political Science and ...
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### What questions or areas in the foundations of mathematics remain active research fields?

By foundations of mathematics I am referring to the mathematical, logical, and philosophical foundations of the subject. I'm interested in seeing which of these have active research going on within ...
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### Can Kant's antinomies be translated into formal logic?

Kant proves the limits of human reason by providing 4 antinomies, pairs of rational but contradictory statements, which he claims pure reason can never help us decide which one of the pair is correct. ...
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### Is Logic Pre-Human?

It was German philosopher Martin Heidegger (1889-1976) who famously said, "animals are poor in world." Although this may be true, I do not see them as being poor in logic. Paleontologists have ...
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### Looking for references for some remark of Quine's

I'm looking for a comment I think I remember Quine having made. He's talking about our understanding of proofs. I think he says something along the following lines... If you understand many different ...
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### Why de re modality is a problem for Quine?

I have read that Quine "accepts" de dicto modality because he is able to extensionalize it. But I have also read that Quine rejects de re modality because it is not extensionalizable and because in ...
31 views

### Logic terminology: does “conditional” etc refer to the operator or the WFF?

To be precise.... Do the terms we use to talk about the truth-functional operators (conditional, negation, conjunction, disjunction, biconditional) refer to the operator in isolation, or the WFF that ...
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Semantic Anti-Realists hold that a claim has a (constructive) proof if the claim is true. I wonder whether this position runs into a version of Yablo's supposedly non-circular version of the liar ...
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### What are some benefits of a second order logic?

I have read that a second-order logic can help one define equality by quantifying over all predicates such as what is done in the following definition: (x=y):⟺[∀P:P(x)⟺P(y)] By contrast a first-...
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### How disjunction works with the conditional excluded middle

I'm studying the semantics for counterfactuals, and I'm slightly confused about how certain inferences supposedly make the Conditional Excluded Middle (CXM) fail. Formally, we can write the ...
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### Using solipsism's incoherence with doubt as proof of the external world?

I have the following rough outline of utilizing solipsism as a proof by contradiction to the goal of asserting an epistemological proof of the external world. A solipsist (Wittgenstian) lives in a ...
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### Which philosophers proposed theories containing a performative contradiction?

Socrates was blamed of this by being wrongly interpreted of saying: "I know that I don't Know." or other variants. What he really said was: "I neither know nor think that I know." Source: https://en....
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### ELI5 - Abduction vs. Inference to Best Explanation (IBE)

How can you explain to a 5 y.o. how abductive reasoning differs from IBE? I don't understand even though I read SPE and these papers: Campos, Daniel G. On the Distinction between Peirce’s Abduction ...
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### Can a Rigid Designator still exist if there is only one possible world?

According to Kripke, a rigid designator is a pronoun (but not all pronouns are rigid designators) and they pick out the same unique individual in each possible world. I understand this, however, if ...
64 views

### Language confusion; necessary/nomological/true in all worlds

I got confused by the way different people use language in the context of physicalism. In particular, Kripke seems to equate "necessary truths" with something that is true in all possible worlds. Is ...
120 views

### Modal logics - philosophical paradoxes using modeling by possible worlds

I'm searching for "paradoxes" in classical modal logics, meaning lines of reasoning which give a counterintuitive conclusion if performed in classical logic, which can be modelled by the (semantical) ...
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### Circularity between truth and meaning?

These two common claims are equally appealing: (1) the meaning of a ( declarative) sentence consists in its truth conditions (2) the truth of a sentence depends on its meaning But are we moving ...
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### Is there an Abstract/Concrete Gray Area?

In natural language and daily life, it has become prevalent there is a class of entities which do not follow the abstract concrete distinction. Many people refer to abstractions that exist in time. (...
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### How did Aristotelian logic view this?

I am very interested in the logical aspect of Aristotelian philosophy, especially how it was used by al Farabi and Ibn Sina in explaining understanding and breaking this complicated process down ...
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### Why is a square circle metaphysically impossible?

We have definitions for both a square and a circle. By definition, I understand that it's impossible to have a square circle. However, why does the word 'square' have to necessarily mean 'a plane ...
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### Prove that if the tree method determines that a set of sentences T implies a sentence A, then T does in fact imply A

Having trouble wrapping my head around how to prove this. My first question about this is what it means for the tree method to determine that the set of sentences implies A. I'm taking it to mean that ...
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### Why don't two equivalent propositions contribute to the same semantics?

We often have 2 propositions that have the same truth table, in that they are true and false given the same conditions. Nevertheless, we still feel as though there different semantics (i.e meaning..),...
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### Does Reflective Set Theory “RfST” fulfill the requirements of founding Category Theory and Mathematics?

On mathoverflow I've posed the question in the title in connection to Muller's 2001 criteria for a founding theory of mathematics, which largely raised in connection to Category theory [see here]. ...
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### Why can't existence be expressed in linear temporal logic?

In some circumstances, existence cannot be expressed in linear temporal logic. I don't understand why it can't be constructed with negations and global quantifiers. For example, the wikipedia page (...
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### Is there such a thing as unary logic?

Is there such a thing as unary (as opposed to binary, ternary, …, n-ary) logic? cf. Is there any reason for the heavy focus on binary relations in formal logic?
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### Syntactic and semantic eliminability/conservativeness

Let L be a ground language, and L+ the extension of L with additional signature terms and axioms. We say L+ is syntactically conservative over L if every sentence in L that is provable in L+ is ...
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### Is there a connection between argument diagramming and formal logic systems such as propositional/ predicate logic?

Early in most logic textbooks you find what I see as a very useful tool for understanding arguments called "argument diagramming." This is where you find the premises and conclusions, give them ...
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### Axioms for modal logics based upon counterfactuals

Suppose we have a logic for counterfactuals as with David Lewis. I here use ⇛ for the counterfactual conditional. So suppose we have: Rules: (1) If A and A→B are theorems, then B is a theorem. (2)...