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
162
votes
15answers
42k views

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 ...
73
votes
8answers
11k views

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 ...
63
votes
6answers
12k views

Logical fallacy: X is bad, Y is worse, thus X is not bad

I have heard this type of argument too many times: You are criticising X using well researched facts and arguments. Your interlocutor, states that Y is much worse with equally well researched facts ...
63
votes
12answers
15k 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 ...
56
votes
21answers
13k views

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 ...
46
votes
12answers
20k 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 ...
41
votes
9answers
13k views

What fallacy in Pascal's Wager allows replacing God with the devil?

I wanted to know the name of the fallacy or fallacies the Pascal's Wager in the sense that it can be applied to motivate one's belief in many things. A similar argument to the original Wager can be ...
40
votes
15answers
14k views

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 ...
40
votes
16answers
10k views

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’...
36
votes
11answers
14k views

Is it a fallacy if someone claims they need an explanation for every word of your argument to the point where they don't understand common terms?

Is it a fallacy if someone claims they need an explanation for every word of your argument to the point where they don't understand common terms? For example, suppose someone said, "If a dog bites ...
35
votes
10answers
7k views

Is it a fallacy, and if so which, to believe we are special because our existence on Earth seems improbable?

People often use the argument that there must be a God, for example, because Earth and the laws of physics are perfectly situated for humans to exist the way we do. However, if Earth or even the ...
35
votes
12answers
14k views

Is circular reasoning always a fallacy?

Suppose the following dialogue: ... "I accept only one notion of land property. Namely, 'I am doing my stuff here, therefore I am here". "But this means," he responded, "you can break ...
34
votes
17answers
12k views

Why doesn't philosophy have higher standards for its arguments?

Mathematical systems are an excellent model for organizing and conducting thought: In the mathematics community, any argument in support of a conjecture, that deviates from "sound argument" never ...
34
votes
13answers
5k views

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 ...
32
votes
3answers
3k views

Is First Order Logic (FOL) the only fundamental logic?

I'm far from being an expert in the field of mathematical logic, but I've been reading about the academic work invested in the foundations of mathematics, both in a historical and objetive sense; and ...
30
votes
3answers
4k views

How did first-order logic come to be the dominant formal logic?

Early formal systems like Frege's Begriffsschrift or the Peano's work on the axiomatization of the natural numbers used axiom system with an underlying second-order predicate logic (from today's point ...
29
votes
9answers
18k views

What is the difference (if any) between “not true” and “false”?

A fairly simple question I hope someone can help me with.
29
votes
5answers
8k views

Is “I cannot imagine a mechanism for X to happen, so X can never happen” a named logical fallacy?

I have encountered this reasoning quite frequently: Somebody posits the hypothesis that an event X can happpen. A recent example I encountered was "vinegar and salt in the boiling water make eggs ...
28
votes
3answers
3k views

How is Gödel's incompleteness theorem interpreted in intuitionistic logic?

Classically, one sets up an axiomatic system with a formal deduction system & an interpretation in a model. Generally it is sound, that is: a formally deduced theorem is also true when interpreted ...
27
votes
9answers
188k views

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 ...
26
votes
3answers
1k views

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 ...
25
votes
15answers
2k views

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 ...
25
votes
4answers
4k views

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 ...
24
votes
11answers
11k views

How is gun violence comparable to drunk driving?

I just read "Is 'guns don't kill people people kill people' a good argument?" and it reminds me of another argument. I would like your opinion on whether or not it is a good argument. Gun Control ...
24
votes
4answers
4k 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 ...
22
votes
10answers
10k views

Can an argument be valid even though one of its premises is false?

Is it possible for an argument to be valid by virtue of its logical form, but contain a false premise? In other words, can a premise be false even though the argument itself is logically valid? ...
22
votes
10answers
4k views

Is it a fallacy to say that a sane person cannot apply rational thought to the motivations of the insane?

A common argument in today's news is that: Someone commits a heinous crime by shooting a bunch of people. Anyone who commits a heinous crime must be insane. Sane people cannot apply rational thought ...
22
votes
6answers
9k views

How is the argument “I love all logic, but I don’t love deductive reasoning. Therefore, the moon is made of green cheese.” valid?

This example came up in class: I love all logic, but I don’t love deductive reasoning. Therefore, the moon is made of green cheese. I understand the premise is contradictory and the conclusion ...
22
votes
10answers
3k views

Are different values of nothing equivalent?

Are different values of nothing equivalent? Is 'no tigers' the same as 'no zebras'?
22
votes
12answers
4k views

Are there any philosophy books for an intelligent nine-year-old?

I would like to buy some books on philosophy for the child of a friend. He is very intelligent and mathematically able and clever for a nine-year-old. I remember near that age really enjoying the idea ...
21
votes
15answers
4k views

Is there any rigorous philosophical basis for atheism?

Definition/Update In what follows I use the term God to refer to an entity that has at least one of the following properties: Has created the universe Is omnipotent Is omniscient Approaches to ...
21
votes
10answers
5k views

Why can't humans believe contradictions?

I'm reading something on the topic of logic and one of the exercises asked me to convince myself that a contradictory statement was true. I could not convince myself of this and now I am curious about ...
21
votes
12answers
2k views

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 ...
21
votes
3answers
17k views

What is modal logic for?

I understand "pure" logic as a structural description of what a valid proof is but I have never understood the reasons for using modal logic. What's an example typical of how modal logic is used?
21
votes
4answers
33k views

What is the difference between a statement and a proposition?

I'm doing a MOOC on mathematical philosophy and the lecturer drew a distinction between a proposition and a statement. This is very puzzling to me. My background is in math and I regard those two ...
20
votes
10answers
3k views

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 ...
19
votes
8answers
26k 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 ...
19
votes
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 ...
19
votes
2answers
7k views

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 ...
18
votes
12answers
21k views

Have I found a paradox, or is the universe digital? Or am I just plain wrong? [closed]

If the universe is analog, there must exist an infinite number of positions. This raises an interesting question. Let me boil it down to something familiar: a table and an ashtray. I'll let the ...
18
votes
7answers
5k views

Selection of logical connectives {¬,∨,∧,⇒,⇔} in set theory?

Nearly every treatment of set theory, whether Paul Halmos' Naive Set Theory, Herbert Enderton's Elements of Set Theory, Patrick Suppes' Axiomatic Set Theory, etc. introduce a common set of logical ...
18
votes
3answers
2k views

Why does Carnap say 'Caesar is a prime number' is meaningless?

I don't get it. Assuming there exists an individual Caesar, we can look at the set of prime numbers and not-(prime numbers), and Caesar will be in one of them. I just don't see, even though it may be ...
18
votes
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 ...
18
votes
1answer
1k views

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 ...
17
votes
7answers
6k views

What's the name of the logical fallacy where a debater extends a statement far beyond the original statement to make it true?

Suppose that someone initially states that "fossil fuel consumption due to mobile phone usage is similar to that of private transportation, so if you think we should switch to electric/bike to fight ...
17
votes
4answers
4k views

Is there any worth—other than historical—to reading Aristotle's works on logic?

What I mean is that presumably a topic such as logic would have, at this point, been so advanced that the ancestral works are unnecessary. I would read it for pleasure, but have they been ultimately ...
17
votes
6answers
2k views

What fallacy dismisses criticism of a bad law with “just don't break it”?

Let's say someone is criticizing the government for instituting some draconian policy, and/or for persecuting people for doing something minor. And the response is:"Just don't do it and you'll be fine"...
17
votes
5answers
5k views

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 ...
16
votes
8answers
7k views

How is the claim “I am in New York only if I am in America” the same as "If I am in New York, then I am in America?

It makes absolutely zero sense to me. It would make sense if "I am in America" is the antecedent and the consequent is the former. Even though it wouldn't be sound, it would make logical sense. I ...
16
votes
7answers
3k views

Are all paradoxes reducible to one “fundamental” paradox?

I may need to refine this question, since I am mostly grappling with a murky intuition and haven't yet done the real work. When I encounter many of the well-known paradoxes, such as Zeno's dichotomy, ...