# 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 can we have a 'natural existence' for complex numbers? [closed]

For those who don't know what a complex number is, in simple terms, a complex number is the square root of a negative number! For example, the square root of -1 is called a complex number. Those ...
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### Are different values of nothing equivalent?

Are different values of nothing equivalent? Is 'no tigers' the same as 'no zebras'?
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### What are the major research programmes in contemporary logic?

As an interested outsider who is prone to reading about different formulations of logic, I've become interested in better understanding the big picture of what people are trying to accomplish as they ...
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### What is the sense of the phrase “(no) fact of the matter about/as to”?

Could someone explain to me what exactly is meant by the phrase "fact of the matter about" (or "no fact of the matter about")? Another variant is: "(no) fact of the matter as to". In some cases, ...
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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 ...
444 views

### Is there a logic that takes time into account?

I hope this is neither too simple nor off-topic; I apologize if so. I have just noticed that standard sentence logic seems to make assumptions about time in determining the truth/falsity of a ...
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### Does it make sense to think that algorithms can be specified only for all that which is manmade? [closed]

I've been asking myself the following question over and over again: can one write an algorithm (a series of steps for solving a problem) for something that came about through a process that is at ...
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### Is it possible to generate logically valid sentences made up of “atomic contradictions”?

Is it possible to generate sentences that are made up of "atomic contradictions", but which remain logically valid as a whole? By "atomic contradictions", I mean atomic propositions that are not ...
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### Hempel's ravens (the confirmation paradox) [closed]

While taking a group of benefactors on a tour through the new aviary they had just helped to build, a noted ornithologist commented, "And here we have two of the finest examples of ravens that I have ...
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### What is a mathematical representation of the physical world?

Possible Duplicate: Was mathematics invented or discovered? To be more precise, does mathematics describe the physical world or does it describe a mental representation of the physical world? If ...
281 views

### What is fallacious about an argument that “I know X well, so she is right”?

I often hear from media personalities that they are right about a theory or assertion merely by associating themselves with someone or something. For example: "I know Mr. X very well (for years) and ...
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### Is it possible to deny that affirming a logical contradiction implies every possible proposition?

I find myself aligned with the motivation behind paraconsistent logic, they seem to me reason enough to warrant an attempt to structure logical systems which deny logical explosion. It does seem very ...
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### Why would definition not be proposition?

I've read in one mathematics book that any definition is not a proposition. Why is it so? What definition of proposition makes the former into the latter? EDIT: There is well-known analytic-syntactic ...
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### Does the law of excluded middle follow the law of excluded middle?

Example is that the word unknown is not unknown so it doesn't define itself. Similarly French is not French, it's in English, and "long" is not long and only 4 letters short. That's by example my ...
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### Is always lying about everything a consistency?

Here is another question I didn't get a clear answer to when the term "consistency" is applied in philosophy, logic and computer science. Is always lying consistent since we know the statements are ...
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### Is illogical = not logical?

I think law of excluded middle makes sense to mean that a statement should be either logical or illogical but in this case I don't assume "not logical" = "illogical" since the author didn't say "...
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### Should Wittgenstein be given some credit for Godel's incompleteness theorem?

Is there a connection between Wittgenstein's argument against the "Theory of Types" and the proof of Godel's Incompleteness Theorem? Being only semi-knowledgeable, I will draw the connection of which ...
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### Can a lack of knowledge or understanding invalidate a positive claim?

Consider the example of causal determinism. It can be phrased in many ways, all with identical meaning: - The idea that "every event, including human cognition and behavior, decision and action, is ...
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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 ...
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### Language as barrier to concepts [closed]

Can the limitations of language be considered a barrier in conveying a philosophical concept? How can an idea that resists linguistic formulation be conveyed without losing the essence? Is there a ...
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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 ...
826 views

### Is the argument that a claim is “too strange to be made up” an appeal to logos or pathos?

When someone tries to persuade you of the truth of something they said and they use the argument that it is too strange to be made up (or any variations of this, such as "too complicated to be fiction"...
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### What does Hegel mean by “Quality”?

In the Science of Logic, Hegel initially presents quality as existent determinateness. He further distinguishes two modes of determining quality in accordance with the moments of existence: ...
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### Is reductionism the primary means of logical analysis in analytic philosophy?

I was reading a philosophical article about analytic philosophy and I saw the claim: Russell and many philosophers influenced by him asserted that complex statements can be reduced to simple ...
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### Where is the weakness in the ontological proof for God's existence?

I read the ontological proof for God's existence. As much as I understood, it says that if you consider that existence is part of essence, then the most complete essence should also exist. Now, I see ...
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### What does it mean that a claim is a claim of nonexistence?

This question has devolved into a discussion. As I understand the discussion, everything is revolving around the veracity of statement Nonexistence can never be proven. and on what exactly ...
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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 ...
551 views

### Are systems of logic that don't follow or extend garden-variety FOL possible?

As I know all humans share a unique logic and even less-educated people uses same common sense in their statements. For example, it is rational for anybody that if P is correct then P or Q is correct ...
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### What is the difference between “reductio ad absurdum” and “proof by contradiction”?

What is the exact difference between reductio ad absurdum and proof by contradiction? Wikipedia used to state that: Reductio ad absurdum (Latin: "reduction to the absurd") is a form of argument in ...
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### Does philosophy belong to empirical science or formal science?

According to Wikipedia, science can be divided into empirical science (such as natural science and social science) and formal science (such as mathematics, logic, statistics). I was wondering if ...
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### An immovable object and an irresistible force [closed]

If an immovable object is an object that cannot be moved no matter what and an irresistible force can move anything, what would happen if an irresistible force is used on the immovable object?
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### When it is correct to use Tarski's undefinability theorem versus Gödel's incompleteness theorem?

Smullyan (1991, 2001) has argued forcefully that Tarski's undefinability theorem deserves much of the attention garnered by Gödel's incompleteness theorems. That the latter theorems have much to say ...
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### Are there any potential flaws in the definition of validity as “provable or falsifiable”?

I have made an argument in another thread that a proposition must be provable or falsifiable to be valid. Are there any flaws in this definition of validity? What might be a potential counter-argument ...
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### What is the philosophical equivalent of mathematical proofs?

In mathematics, there seem to be five standard methods of proving or refuting an argument: a proof by induction, contradiction, counter example etc. Are there some typical proof methods that exist in ...
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### Is the claim “this coin is fair” falsifiable?

Wikipedia says, The claim "No human lives forever" is not falsifiable since one would have to observe a human living forever to falsify that claim. Thinking on similar lines, even if the ...
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### What's an intuition for material implication?

The paradoxes of material implication show that the usual interpretation of implication as "if ... then" statements leads to counter-intuitive results. For example, from (P & Q) -> R we can ...
633 views

### What is an 'argumentum ad baculum'? [closed]

I've seen philosophical arguments descriped as 'argumentum ad baculum', but never quite understood what the criticism is trying to indicate. As best I can tell, it's using force or the threat of force ...
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### God's paradoxes and their implications [duplicate]

Possible Duplicate: Is the definition of God consistent? As many of you, I've come across a few paradoxes of all sorts, from logic to math, linguistics and so forth. Some of such involve God or, ...
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### What is an 'argumentum ad lapidem'? [closed]

I've seen philosophical arguments descriped as 'argumentum ad lapidem', but never quite understood what the criticism is trying to indicate. As best I can tell, it's a dismissal of an argument with ...
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### What is a “straw man” argument? [closed]

What is a "straw man" argument? Assuming an interlocutor is utilizing such an argument against you, what are some techniques for countering it? What motivations might lie behind a disputant using a ...
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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 ...
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### Is there any possible world in which 2+2=5?

Gödel's incompleteness theorems show that arithmetic is either inconsistent or incomplete, and that arithmetic cannot prove its own consistency. It is useful to believe that arithmetic is consistent, ...
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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. ...
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### Is Kurt Gödel's Incompleteness Theorem a “cheap trick”?

I found a throw-away critique of Kurt Gödel's Incompleteness Theorem in an essay about Deconstruction: The basic enterprise of contemporary literary criticism is actually quite simple. It is based on ...
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### What's the relevance of falsifiability in regards to logical arguments?

Is it reasonable to classify logical propositions that rely on deduction and are non-falsifiable as being inherently not worthy pursuing or does this just applies to inductive reasoning?
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### Is 'equality' ultimately grounded in empirical observation?

Let's say I invent a concept X in my own imaginings. The only property it has is X-ness; it is defined as 'that which is represented by X'. I have just defined that to be the case. It seems to me, ...
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### 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 ...