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Questions tagged [logic]

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

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Is the “omniscient-omnipotent-omnipresent” definition of God consistent?

God is commonly defined as an omniscient (infinite knowledge), omnipotent (unlimited power), omnipresent (present everywhere) entity. Is there any logical inconsistency in this definition? I have ...
20
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1answer
11k views

How can we reason about “if P then Q” or “P only if Q” statements in propositional logic?

When you have a propositional sentence of the form P ⊃ Q  — which we might read as "if P, then Q" — how can you tell when it is true, or false, based on the truth-values of P and ...
27
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9answers
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What is the difference between Fact and Truth?

I'm curious about the difference between Fact and Truth. I was searching on the internet if I could find it. But still I'm confused about the exact meaning. I first read the forum discussion here Fact ...
64
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12answers
14k views

Can you prove anything in philosophy?

I don't understand philosophy very well, and so I am wondering whether you can "prove" anything in philosophy. It always seems you can go a layer down, and find another question, almost endlessly ...
35
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13answers
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What are the necessary conditions for an action to be regarded as a free choice?

A common philosophical question revolves around the existence of free will, but what I've found is that these debates seem to gloss over the concept of "free will" itself, either taking it as a given ...
16
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2answers
14k views

What fallacy dismisses problems by presenting “bigger” problems?

Wasn't really sure how to phrase this, but I'm thinking of an instance in which someone diminishes a problem by presenting one of larger scope - as a rather shoddy example, "x political problem in ...
40
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13answers
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Does a negative claimant have a burden of proof?

I have often heard it said that the burden of proof is on the positive claimant but not on the one making a negative claim. A person claiming, "God exists" has a burden of proof but not a person ...
18
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6answers
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Is God either immoral or not omnipotent?

The usual (Christian) justification for suffering/evil in the world created by a benevolent God is freedom of the will. However, the more interesting question is not about the source of evil (which ...
16
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7answers
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Is infinite regress of causation possible? Is infinite regress of causation necessary?

For a number of reasons — including perhaps a desire to feel that we have a complete understanding of where we came from, or at least an understanding which is completely sufficient for all of ...
10
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2answers
5k views

What are the more complex/interesting examples of synthetic a priori statements?

The usual examples of synthetic a priori statements are – it seems at least since Kant: "Nothing can be simultaneously red and green all over" 7 + 5 = 12 (or any other basic arithmetic statements). ...
8
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2answers
3k views

How do I check if two logical expressions are equivalent?

For example: Is (A ∨ B ∨ C) ∧ (D ∨ E ∨ F) the same as (A ∧ D) ∨ (A ∧ E) ∨ (A ∧ F) ∨ (B ∧ D) ∨ (B ∧ E) ∨ ( B ∧ F) ∨ (C ∧ D) ∨ (C &...
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16answers
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How to get started with philosophy without getting overwhelmed quickly?

I’ve spent a lot of time trying to find how to get started with philosophy but I can’t. It seems that getting started with computer programming is nothing in comparison - with computer programming it’...
9
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2answers
669 views

What are the differences between philosophies presupposing one Logic versus many logics?

I was wondering in light of the historical developments of logic since ancient Greeks and well into the nineteenth and twentieth centuries: What kind of a philosophy assumes only one Logic, and what ...
6
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12answers
13k views

Is it possible to know anything with certainty?

I have been thinking about objectivism vs relativism recently. It is easy to prove by contradiction that there exist objective truths. However, is it possible to know anything? If you assume a human ...
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4answers
1k views

What is the logical form of the definition of validity?

My text book gives the definition of validity as "An argument is valid IFF if the premises are true, then the conclusion must be true". Using a conditional elimination on the RHS of the IFF yields "An ...
19
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8answers
25k views

What is the difference between “necessary” and “sufficient”?

What is the logical difference between something being necessary in order for something else to be true; as opposed to something being sufficient to make something else true. i.e. Fuel is sufficient ...
4
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6answers
521 views

Is the use of inconsistent definitions a logical fallacy?

I am not asking for a defense of or pro/con of the existence of an omnipotent (or multiple omni-x) being, or for the existence of square-circles or any other similar thing. These arguments are well ...
7
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3answers
577 views

Is there modal logic without possible worlds?

Would it be desirable to carry out a deflationary research programme in modal logic? In other words, would it be desirable to re-think modal logic without the possible worlds semantics? The original ...
8
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5answers
650 views

What fallacy dismisses a conclusion because supporters give invalid arguments for it?

A person dismisses an otherwise valid argument, because some of its proponents support it for the wrong reason. How is this fallacy called? EDIT: Here is an example. A person defends the idea that ...
4
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6answers
2k views

Can logic be used to prove any belief?

I have witnessed a lot of debates and arguments of different beliefs, and noticed that each side uses logic to prove its point. So, can any belief be proven by logic regardless of its nature (...
19
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7answers
2k views

What formal logical systems “resolve” the Liar Paradox?

Short version of my question. What formal logical systems can represent, and seem robust against, the Liar Paradox? N.B. I would like to avoid reference to truth-values, except inasmuch as they ...
4
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4answers
924 views

Is logic subjective?

If logic is constructed from axioms, and axioms are depended on observation which in term could be subjective, does this means that logic could be limited to our observation, and not really absolute ...
13
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3answers
402 views

Do all epistemologies suffer from the “regress of justifications” problem?

Aristotle describes the regress problem in his logical work Posterior Analytics I.2: b5. Some hold that, owing to the necessity of knowing the primary premisses, there is no scientific knowledge. ...
7
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2answers
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Are arguments based on conceivability refuted by ideas from fantasy and sci-fi?

There are several arguments in metaphysics which are based on "conceivability": The ontological argument for God's existence. Hilary Putnam's Twin Earth argument for semantic externalism (the idea ...
3
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1answer
380 views

Is there a suppressed premise in Anselm's Ontological Argument?

Source: 5 minutes 20 seconds juncture; Lecture 1, Video 4 (transcription); MITx: 24.00x Introduction to Philosophy; by MIT Associate Prof Caspar Hare PhD (Princeton) [...] Suppose God existed in ...
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2answers
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What is the philosophical ground for distinguishing logic and mathematics?

I was wondering why the field of mathematics and that of logic are perceived as two distinct fields. Although could be pleased with the intuition that logic is rather meta-mathematics, still would ...
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12answers
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Motivations for dialetheism?

At the request of the moderators, I've reformulated this question to change the emphasis of the question to something perhaps a little more broad-ranging: Question. What are the major modern ...
13
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2answers
346 views

Was Locke right that analytic knowledge is vacuous?

According to Locke, it is impossible to obtain substantive knowledge from analytic propositions. Statements like "triangle has three sides" are analytic, but one cannot derive the Pythagorean Theorem ...
7
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2answers
475 views

Is free will a third option aside from chance and necessity?

The determinism dilemma is that if our actions are predetermined they are not free, and if they are random they are not willed, either way there is no free will. Even if will causation is a mixture of ...
7
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5answers
2k views

Why are conditionals with false antecedents considered true?

I don't understand what conceptual sense this scenario makes, or what the motivation behind the decision to make conditionals with a false antecedent true was. Can anyone help me understand this? ...
7
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3answers
367 views

Why is Tarski's notion of logical validity preferred to deductive one?

Its flaws are well-known and serious. To recall, an inference from A to B is valid iff all interpretations of "non-logical constants" that make A true also make B true. What are interpretations, a.k.a....
4
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8answers
381 views

Intuitively, why does (B → S) ≡ (¬B ∨ S)?

I pursue only intuition; please do not answer with formal proofs or Truth Tables. I comprehend the following explanation, but it still does not supply the intuition and I sense a deeper, directer, ...
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2answers
816 views

Can paraconsistent or other logics make the impossible happen?

A paraconsistent logic system it is defined as "a logical system that attempts to deal with contradictions in a discriminating way. Alternatively, paraconsistent logic is the subfield of logic that ...
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15answers
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Is 'guns don't kill people, people kill people' a good argument?

I'm hearing the argument X doesn't do Y people do Y in quite a few guises. For instance in it's original form guns don't kill people; people kill people Presumably, therefore guns are OK cars ...
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7answers
2k views

Is Logic Empirical?

We use the logical system that we know from observations (empirical data) holds true in the world we live in (please correct me if I am wrong). Hence the axioms of logic we choose are themselves ...
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8answers
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How to justify the use of logic?

I would like to hear some Philosophical arguments which justify the use of logic. Additionally, if a justification of logic takes the form of an inference, this inference itself makes use of logic. ...
7
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5answers
943 views

How does actual infinity (of numbers or space) work?

Is infinity just continuous generation of numbers, or can space be actually infinite? If it is finite can we see it expand if we went to the edge? When I say "I am counting to infinity" does it mean ...
13
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2answers
702 views

What are the current topics in philosophy of logic?

I'm contemplating another attempt at completing my long delayed MA in Philosophy, and I need a new thesis topic. As a student I excelled in advanced symbolic logic, but my connection with academic ...
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3answers
1k views

Where is a good place to start reading about logic?

I would like to learn logic as an introductory subject. I am an undergraduate student and would appreciate any suggestions for books/articles where I can start from, also any books/articles about ...
6
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2answers
767 views

What is the relation between the material conditional in logic and conditionals that we use every day?

The material conditional has a truth-value of T in every case except where the antecedent proposition is true and the consequent is false. However, this means that many conditionals are true (if only ...
4
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3answers
685 views

How does free will defense of God's benevolence work?

The purpose of the defense is to show that omniscient, omnipotent and benevolent God is consistent with the existence of evil in creation. The most popular version of the defense is due to Alvin ...
4
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4answers
940 views

Validity of an argument with a contradictory conclusion [duplicate]

I have an argument with the conclusion: 'The sky is blue and it is not the case that the sky is blue'. Without knowing the premises of this argument, am I right in saying this argument is invalid ...
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3answers
1k views

Why do we take deductive and inductive reasoning for granted?

In philosophy, we doubt everything, even the things which seem obvious and intuitive. So why do we accept deductive and inductive reasoning without doubting their validity?
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3answers
519 views

Deduction vs Induction — are they equally valid?

I've been reading on deduction vs induction as two primary modes of reasoning. Can't exactly remember where but I have also seen deduction being described as backward and induction as forward thinking....
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4answers
3k views

What are the philosophical implications of category theory?

I have heard about topoi being the ideal entities to use for foundations of mathematics (since we are able to reasonably interpret our theories in them), so I imagine there might possibly be some ...
46
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12answers
19k views

Does Pascal's Wager contain any logical flaws or fallacies?

Blaise Pascal's famous wager was that even if the existence of God cannot be determined through reason, a rational person should wager as though God exists, because living life accordingly has ...
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11answers
3k views

How fundamental is logic?

I had always perceived logic as something that exists outside mathematics, physics/the physical, human consciousness, and everything. So when someone in my class posed the question whether logic can ...
13
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12answers
15k views

Are omniscience and omnipotence mutually inconsistent?

I see this in The God Delusion by Richard Dawkins: If God is omniscient, he must already know how he is going to intervene to change the course of history using his omnipotence. But that means ...
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10answers
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Is the universe isomorphic to a universal turing machine?

I often think about problems that require an understanding of the very essence of computation and its inherent limitations. So, my questions are as followed: Is the universe isomorphic to a universal ...
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9answers
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When can we call an explanation “rational”?

There are a lot of questions involving rational judgment, rational choice, rational explanation, etc... And at the same time, it seems that "being rational" is a guiding principle for a lot of people. ...