Questions tagged [logic]

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

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How does one understand the second and third triad in Hegels Logic?

The first dialectical triad in Hegels Logic and put in a mathematical form is Being + Nothing = Becoming Although a strange sum, I find this understandable. His second dialectical triad takes the ...
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Reduced model of society

When astronomer, stars observer live in a city, they say: "Those artificial lights in the city, they confuse us, we are going out of this place, there the disturbing influences are fewer." When a ...
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Dictionary English - logic/formal symbols/expresssions

I'd like to know whether there's some kind of database offering the logic or formal" equivalent of English expressions, for example the conjunction "whereas", which has at least two meanings, each ...
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Is this a valid argument (using probability and uncertainties)?

If A, then B (probability of 0.6 that this is true) If B, then C (probability of 0.6 that this is true) A, Therefore C. I'm not sure whether C is probably true if A is true, or if the probability ...
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Quantificational vs Referential vs Predicational descriptions

Reading Peter Ludlow's article on descriptions, it's clear to me that descriptions can be interpreted, found or considered in 3 different ways. They can be seen as quantificational, referential or ...
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293 views

Create a statement in propositional logic. This statment must have 2 attributes. (The attributes are specified in the top header)

The following are the 2 attributes: (1) This statement claims the statement after it is true. (2) This statement cannot be not true. This statement would achieve these 2 attributes through its ...
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186 views

The sea battle paradox and the soundness criterion

Again a short look at Aristotle's resolution (one of many) of the sea battle paradox: In one famous example about a hypothetical sea battle, [Aristotle] observes that the necessary truth of a mere ...
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148 views

Hypocrisy and Ad Hominem

I have a little question on logical fallacies and ad hominems. There's this problem: Person A and B are both hypocrites; they're both aware of this. Person A argues that B is a hypocrite, and ...
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How may Nikolaus von Kues’ “concept of concept” be applied as a bridge between logic and theology?

I am neither a specialist for logic nor for theology. Yet, I was electrified about Nikolaus von Kues statement that God is the concept of concept. Has Kues’ proposition somehow been applied as a real ...
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45 views

Are semantic inferences between undecidable sentences in a system possible?

For example from the Gödel sentence "G iff ¬P([g])", where g is G's Gödel-number, is it possible to make semantic inference (not syntactic, only at the level of truth between the undecidable sentences ...
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87 views

How do we define a fact?

Got into a discussion today with my Semiotics professor regarding this question and I still had questions in my head on the way home. He was stuck on the notion that facts have just become things ...
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215 views

Axiomatic Proof of Symmetry and Transitivity of Identity

Given the axioms below and the rules of Modus Ponens and Universal Generalization, how can you prove that t=s → s=t for any terms s and t? Additionally, how do you prove that t = s → (s = r → t = r) ? ...
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Trees/tableaux fir K-IF logic

Are there any attempts for tableaux/ tree rules for Hintikkas K-IF logic?
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What consequences (types of) exist in the real world (categorical monoidal logic)?

Springer book http://www.springer.com/la/book/9783642128202 "New Structures for Physics" (which contains lot of metaphysics despite the physics in its title) elaborates categorical and monoidal ...
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98 views

Sufficient & necessary conditions for singular and general statements

In David Rynin's 1956 address to the American Philosophical Association, "Vindication of L*G*C*L P*S*T*V*SM", he remarks upon the "tenuous logical relationship" between a general statement, "For any ...
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Truth functional propositional logic for “If” in Hunter's Metalogic

I encountered a weird question in Hunter's Metalogic. Here's my reasoning: 'If' in 'If Tom marries Mary, Susan will be unhappy', according to Hunter, is not a "truth functional propositional ...
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35 views

What articles or books are currently considered canonical in the discussion of a priori knowledge and justification?

Quine's "Two Dogmas", I think, would be one. Perhaps also Putnam's "Is Logic Empirical". If you wanted to doubt the existence of a priori knowledge or justification on the basis of the apparently ...
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54 views

How can you intuit Information Implication with 4 Truth Values?

Source: p 158. Sweet Reason: A Field Guide to Modern Logic (2010 2 ed) by Henle, Garfield, Tymoczko. [...] Call this Information Implication. Its truth table looks like this: This ...
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202 views

Omnipotence Paradox Defense and Meinongianism/Neo-Meinongianism

I was considering a solution to the omnipotence paradox in which excluding logical impossibilities from the definition of omnipotence is justified as follows. Consider the proposition, "God could ...
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221 views

What are some active areas of research in proof theory?

Is there any research activity going on in the field of proof theory today? If so, what are some of the most active areas, what types of questions do they deal with, and where can I go to find out ...
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48 views

Is there a symbolic formulation of modal realism?

Is there a symbolic formulation of modal realism, i.e. the doctrines of modal realism captured in some formal system?
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101 views

Using the conception of 'reliable, unchanging' does 'truth' exist?

An 'archaic' definition for TRUE,TRUTH implies constancy, reliability, unchanging, fidelity. Using this concept of TRUTH is the following valid? There exists either that which is TRUE or that which ...
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52 views

Looking for a treatment of multiple interpretations in Model Theory/Formal Semantics

A sentence, such as a Godel string, can be given any intepretation whatsoever, so in a sense, when communicating, we have to be benevolent about the interpretation function that we infer our co-...
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What does *remediable* mean to philosophers? (Example and context provided)

In his essay, Knowledge of Logic, Paul Boghossian writes Finally, on the inferential path, there is the question whether it is irremediably true that rule‐circular arguments provide no ...
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75 views

In Jain Logic what 'is' or 'can be' asserted to be true and indescribable?

Classically a truth value is asserted of a proposition: thus by its very nature it must be describable. Jain Logic has a 'truth value' which is asserted to be true and indescribable; by the above it ...
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Concrete Examples of Complex Term Analysis Using Predicate Logic

In all of my textbooks, there are no concrete case studies of how one can use predicate logic to analyze specific characteristics of complex terms. I am therefore looking for an exemplar for the ...
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1answer
45 views

Quick question on validity of arguments across propositional and predicate logic

Could someone clarify a quick question regarding the following please? From the text: Assume Γ ⊭ ϕ. Then there is an L2-structure A such that all members of Γ are true in A and ϕ is false in A. ...
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42 views

Social Constructivism and Logical Necessity

I am after some kind of reading list on the topic of logical necessity and social constructivism. Any recommendations? I'd like to be in a position to argue cogently that social constructivism can ...
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1answer
353 views

How to self-learn legal arguments, logic, and reasoning?

What are some readable, eloquent (without legalese) books on arguments, fallacies, logic, and reasoning, as applied and used in law? This question is aimed towards a greenhorn/tenderfoot with ...
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1answer
44 views

Logical, semantic and self-referential paradoxes: The Truth teller and the Liar (draft) can an expert on the matter give feedback?

Title: Logical semantic and self-referential paradoxes: The Truthteller and the Liar (draft, informal) (major) assumption: A statement is either true or not true (law of excluded middle, classical ...
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64 views

Inductive Logic on Existence

Because we, only by inductive reasoning, are sure about next moment 'happening' (or more precisely, not worried about it not happening), does this mean that there is no logical guarantee that next ...
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1answer
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Existence and making sense

When faced with a paradox, we say: well this isn't possible because it doesn't make sense. p = "x doesn't make sense" q = "x doesn't exist" The contrapositive preserves validity: p implies q (not q)...
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What falls under Hegel's concept of “absolute knowledge”: does that include deductive logic and scientific explanation?

In the wikipedia page for Hegel's Science of Logic, it states: According to Hegel, logic is the form taken by the science of thinking in general. He thought that, as it had hitherto been ...
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Is is logically inconsistent to say that male on female violence is wrong? (Compared to vice versa)

I have always believed that the reason it is more wrong for a man to hit a woman than vice versa is mainly because women tend to be physically weaker then men, and that even if a women initiated ...
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Can a solipsist doubt?

I've been thinking about epistemological solipsism, which seemingly necessarily follows from metaphysical solipsism. Namely, that the "world" of the solipsist is one and the same with the self of the ...
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Is marxist dialetic according to Aristotle classical logic?

Is a static binary logic compatible with one based on dynamic evolution by overcoming?
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Fitch Proof Help

I'm having some trouble solving this proof in Fitch. How do the universals switch place from the premise to the goal? There is no negation in the goal so negation introduction is not the way to go, I ...
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Some examples of philosophies that consider nonexistence the same as existence?

Can you give me some examples of philosophies that consider nonexistence the same as existence? I thought that maybe some paraconsistent systems (https://en.wikipedia.org/wiki/Paraconsistent_logic) ...
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Finite Alphabets

This is a question based on section 2.5.6 from the book Logic, laws of truth, by Nicholas J.J Smith, page 48. What does Nicholas mean when he says: Note that we can further specify exactly what we ...
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Can hypercomputation compute the impossible?

There are things which are illogical/logically impossible (like saying that 2+2=4 and 2+2=5. Without changing anything in the axioms of mathematics or logic, this would be a contradiction and would be ...
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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
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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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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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What is an example of a monadic predicate calculus argument that cannot be represented by the 19 classical Aristotelian syllogisms alone?

While reading Wikipedia's description of the monadic predicate calculus, I read the following: Inferences in term logic can all be represented in the monadic predicate calculus. and Conversely, ...
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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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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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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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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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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 ...