Logic is the study of formal systems of reasoning, especially of the deductive variety. It is one of the few fundamental philosophical subdisciplines, along with metaphysics, ontology and aesthetics. Logic has taken on considerable importance in recent mathematical developments, and one of the ...

learn more… | top users | synonyms (2)

0
votes
1answer
13 views

How can one determine the overall sentiment of a group of sentences [on hold]

How can one determine the overall sentiment of a group of sentences when you already know how many are positive or negative or neutral. For example you have: Total 100 sentences 60 neutral 30 ...
0
votes
0answers
46 views

Logical Arguments: Why is this Multiple Argument Invalid? [migrated]

In my understanding, an argument is valid when it is the case that if the premises are true, then the conclusion must be true. I have been given the following argument that if n is both a multiple of ...
1
vote
2answers
51 views

Subtly inconsistent axioms

It is not known whether widely used axiomatic systems such as ZFC are consistent and Godel has shown that it is not possible to prove that they are, at least within the system. In an inconsistent ...
4
votes
2answers
80 views

Logic and presentation

In this question I suggested that logic is almost only ever used in philosophy as a means to present an argument. By implication, I meant that every formal argument can be stated informally, and that ...
-2
votes
0answers
13 views

A soft puzzle about a deaf ,dumb and a blind person [migrated]

A deaf person stole a blind person's hen and a dumb person witnessed it.How can the dumb person convey this to the blind person?
2
votes
1answer
54 views

Who invented the notion of Philosophical Zombies?

Philosophical zombies are beings that look like human beings, act like them, drink, eat, talk, and in every other way behaviorally identical to normal human beings. However they have no inner life. I ...
0
votes
3answers
83 views

'Can't answer' as a philosophical response to moral questions

On the Quora forum, there is a question called "Are Some People Better Than Others?" One answer contrasts an altruistic doctor with a selfish criminal, but concludes that there is no real reason to ...
1
vote
0answers
39 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 ...
4
votes
7answers
157 views

What logical fallacy is the argument “I have a RACE_NAME friend, so I can't be racist”?

What logical fallacy is the argument "I have a RACE friend, so I can't be racist"? For example, some people will make this point when trying to defend a comment they made: PERSON A: "I think all ...
0
votes
1answer
34 views

How being unable to settle all disputes makes it possible to settle many disputes?

I'm reading Wieland's: Infinite Regress Arguments. In here: I don't understand how the fail to settle all disputes implies that one couldn't settle many of them. The only possibility I see is ...
1
vote
4answers
56 views

Is it a fallacy to claim someone is committing a fallacy without explaining why?

Making use of an argument about a subject X, Person 1 presents his view to Person 2. Then Person 2, who is against that position, simply makes the following claim: "Hey dude, you have committed the ...
1
vote
3answers
66 views

Logic Question: Symbolizing sentences that use “some”?

How would one go about symbolizing the sentence "some cats are black?" Would I use A: All cats are black and N: No cats are black, in the notation [~A & ~N] so as to say "It is not the case that ...
2
votes
1answer
111 views

Logic problem in TOEFL book

I came across the text about weather system So I think the passage infers that every chaotic system is subset of nonlinear equations weather systems are subset of nonlinear equations chaotic ...
-1
votes
2answers
38 views

Logic question: Is ~(P&Q) equivalent to (~P&~Q)? [closed]

Where '~' is the sign for naught, and stands for "it is not the case that". My question is, is "it is not the case that (P&Q)" equivalent to "it is not the case that P & it is not the case ...
3
votes
6answers
270 views

How can telling the truth amount to a lie? [closed]

According to the Sorites, all men have beards, they just vary in length, density and coarseness. In a loose sense, a beard must have some appreciable length to be considered a beard. Yet, how much ...
0
votes
0answers
49 views

Real in Mathematics Vs Real in Philosophy [closed]

Real is being really analyzed. The two subjects--Mathematics and Philosophy use the term Real. Is there any difference between these two Reals? How can we show their difference using Mathematical ...
3
votes
2answers
90 views

Is it possible to appeal to emotion without commiting a fallacy?

People often make arguments from authority, and not all of them are fallacious. If the given authority is an expert on the discussed field, if there is a consensus among the experts of that field, and ...
0
votes
1answer
31 views

What does Sartre mean with that existence precedes essence and how is it related to the earlier existential philosophers' thoughts?

What does Sartre mean with that existence precedes essence and how is it related to the earlier existential philosophers' thoughts? Existential philosophers like Kirkegaard, Heideggers and Friedrich ...
3
votes
7answers
541 views

Can there be an argument without premises?

After a lengthy discussion with WillO here, we can't seem to find a common ground and I am interested in whether there really could be an argument without a single premise. Another question whose ...
1
vote
1answer
33 views

If all the premises are true and the conclusion is false, is it possible for the argument to be logically valid? [duplicate]

Where an argument is logically valid "if and only if it is not possible for the premises to be true and the conclusion false." Are there any examples of a logically valid argument where the premises ...
1
vote
3answers
133 views

If all the premises of an argument are true, is the argument logically valid?

Where an argument is said to be logically valid "if and only if it is not possible for the premises to e true and the conclusion false". I know that the argument is indeed logically valid if all the ...
0
votes
5answers
101 views

Logic Question: Can a logically valid argument have a logically false conclusion? [duplicate]

Are there any examples of such an argument? What would its premises be like? How could such an argument be possible? Where an argument is logically valid "if and only if it is not possible for all ...
2
votes
2answers
80 views

Is it possible to make non-fallacious argument?

This is a list of fallacies: http://en.wikipedia.org/wiki/List_of_fallacies Looking at this list, I can't imagine any non-trivial, non-mathematical (i.e., not a mathematical proof) argument that ...
0
votes
1answer
19 views

How can I explain the soundness of a rule with respect to the semantics of a truth table?

The question is a mouthful but it comes from an exercise in which I was asked to explain why modus ponens is sound with respect to the semantics expressed by the truth-table. Many things are not ...
-1
votes
1answer
38 views

What is the difference between events and propositions? [closed]

The title says it all. I would be interested as well in references (papers or books). Thank you very much.
0
votes
4answers
129 views

An Argument for the Unity of Truth?

I was thinking about truth, and came up with an outline for an argument that there is only one truth. However, this is just an outline and it is flawed, so I'm hoping you can help me critique and fix ...
2
votes
2answers
55 views

Does being hypocritical or inconsistent invalidate an argument?

While logic is quite important for many things, it seems that many arguments are "won" or "lost" not based on the soundness or lack-thereof of the arguments, but by auxiliary desiderata that I will ...
-1
votes
1answer
53 views

Predicate logic proof

Is the following proof correct: ∀x(Animal(x)<->male(x) v female(x) Animal(a)<->male(a) v female(a) (universal instantiation) Female(a) Animal(a) (modus ponens) ...
0
votes
0answers
20 views

Dual operator in justification logic

In justification logic, given a formula A, one can have modal formulas of the form 't : A', read as 't justifies A' or 't is evidence for A'. Has there been any investigation of what the dual of such ...
2
votes
3answers
50 views

Dual of identity relation?

Does anyone have any intuitions about what the dual of the identity relation might be? I.e. is there a 'natural' concept expressed by a statement such as 'it is not the case that a is not identical to ...
1
vote
3answers
68 views

Infinity time divisibility: Can we observe it and would it disprove ideas of the universe being a simulation?

This question has a basis in what I would call theoretical and metaphysical computer science. Naturally, it would not be welcome on CS SE. Hopefully it fits here and there are those of you here ...
1
vote
2answers
48 views

Multiple quantifiers and negation

In a formula of the form ~ for all x, for all y (l(x,y) -> r(x,y)) how do we apply negation to the formula "(l(x,y) -> r(x,y))" ? And similarly if we have a formula with different quantifiers, such ...
2
votes
1answer
62 views

Universal instatiation and substitution

I've recently read some of the article on first order logic from http://mathworld.wolfram.com/First-OrderLogic.html and im puzzled by the explanation of universal instantiation that the author gives. ...
0
votes
0answers
21 views

similarity between logical indiscernibles and qualia

There are some similarities between qualia (red vs blue) and logical indiscernibles. Basically, that qualia has properties that cannot be described in our language. Has anybody tried to exploit this ...
6
votes
2answers
82 views

What's the difference between :=, =, and ≡?

I understand that ≡ is logical equivalence, "iff". = is a symbol for numerical equivalence. And := is an identity claim. I often only see = and := used with variables and names, while ≡ only appears ...
5
votes
8answers
183 views

Assuming P means the same as Q and Bob believes P and is aware that P means the same as Q, can we conclude he believes Q?

Assuming Bob is a fairly rational person. If this is not the case, then is there a way to modify it? Also, is this the argument that Frege is making in "On Sense and Reference" that "the morning star" ...
0
votes
0answers
21 views

Which are the different possibles and what are their “rules”?

Some time ago I hear about the concept of "metaphysically impossible". It was a surprise for me, then, to hear there are different kinds of possibility, or at least these two "logically possible" and ...
0
votes
2answers
49 views

Is there a name or category for these misleading propositions?

Example I never lost in tennis against Roger Federer. It's a negation and 'true' but it's misleading. In fact I never played tennis against Federer. I'm looking for a name or a category for ...
3
votes
2answers
69 views

English Sentence to Logical Proposition Doubt

I am a newbie to Stack-Exchange and if there is any problem in my question -- I apologize beforehand . I was working my way through some Propositional Logic Questions in Discrete Maths by Rosen , ...
1
vote
1answer
46 views

Fungible Money Question

Suppose that there are two people, A and B. Each has a physical dollar bill. Each donates the dollar bill to an organization. The organization buys something for a dollar. First suppose that the ...
2
votes
5answers
121 views

Can you infer a house exists from the proposition “food cannot be found in any house”?

Give this statement "Food cannot be found in any house (in this area)" Can you correctly infer that "There is AT LEAST a house (in this area)"
-3
votes
3answers
90 views

Is the science Physics allowed to ignore the rules of Philosophy of Science resp. the Scientific Method [closed]

The Scientific Method in Science determines that premises, on which a theory is based, must be experimental verified, when possible. It is however possible that theories of the past are based on ...
3
votes
4answers
118 views

Why is it wrong to deduce determinism from a logical law?

In Aristotle's famous sea battle argument, he argues from bivalence (or something like it) to determinism. Stalnacker has an argument to determinism using standard logical laws, as well. My question ...
0
votes
1answer
44 views

Double arrow elimination

I know that P <=> Q becomes (p => q) ^ (q => p)using double arrow elimination but how about the following ? ~(P <=> Q) becoming ~(p => q) ^ ~(q => p) ? Also (~P <=> Q) ...
3
votes
2answers
151 views

Why does Aristotle suggest One is not a number?

Parmenides showed Nothing is not the same as Zero; the second is a number, and the first is not, in more than one sense; it also differs from the Buddhist notion of Sunyatta, which is nothing in a ...
1
vote
1answer
77 views

Predicate logic and quantifiers

Here are two sentences in Predicate Logic: For all x, there exists a y (If x is F, then x > y) For all x (If x is F, then there exists a y (x > y)) The difference is that in the first example, all ...
-1
votes
1answer
59 views

If philosophical thought didn't existed? [closed]

I am newly interested in philosophy. I am wandering, because of philosophy we got this far today (science, technology and human rights), but is it possible and what if the first men didn't start to ...
0
votes
1answer
30 views

Translate quantifiers into senstance

How can I translate the following into reasonable sentence ? You can let Rxyz stand for anything as long as it makes sense.
4
votes
4answers
174 views

Why is Internet anonymity important?

My grandfather just brought up the topic of requiring all communications on the Internet to be linked to an identity. His logic that all people should be held accountable for their actions is ...
-5
votes
2answers
107 views

What average am I of the five people I spend most time with? [closed]

“You are the average of the five people you spend the most time with.” ― Jim Rohn This quote has been copied and pasted so many times I lost track. But, since I spend most (read: all) of my ...