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Questions tagged [validity]

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161
votes
15answers
43k 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 ...
22
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10answers
11k 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? ...
11
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6answers
2k views

Are there philosophical theories that are either confirmed or refuted by the majority of experts?

Do there exist any philosophical theories that have been either confirmed or refuted by the majority of experts? That is, confirmed or refuted such that a consensus has been established about the ...
10
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3answers
945 views

Does the Scientific Method of research apply to philosophy?

The Scientific Method is essentially the effort to discover causation in perceived correlations of collected data. In other words it hunts for 'recipes' that can be applied to consistently achieve a ...
10
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4answers
661 views

Is Marx's model of capitalist society no longer valid?

Given the evolution of the capitalistic society, to what degree is Marx's model of capitalist society no longer valid nowadays ? Are there any authors which discuss the contemporary validity of Marx'...
7
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3answers
444 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....
7
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1answer
979 views

On the Validity of Modus Tollens

One of the valid forms of argument is Modus Tollens (ie If P, then Q. Not Q, therefore, not P). An example is "If Putnam is guilty, she is lying now. She is not lying now. Therefore Putnam is not ...
6
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5answers
780 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 ...
6
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5answers
6k views

What is the difference between mathematical reasoning and philosophical reasoning?

Please see question in title. Why isn't philosophy considered to be a branch of mathematics? Is study of anything not a branch of mathematics, vague and imprecise?
5
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3answers
1k views

Are “All A is B” and “If A then B” always logically equivalent?

Will "All A is B" always imply "If A then B?" If so, can we say that the following follows the form of Modus Ponens? All dogs are mammals. Toby is a dog. So, Toby is a mammal. Can I rewrite ...
4
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3answers
2k views

If the premises of an argument CANNOT all be true, then said argument is valid

Based on the fact that a deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false, I am ...
4
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4answers
683 views

How to find redundant premises?

Suppose I have this simple argument: ( P ⊃ Q ) R P Therefore, Q Here's the truth table I made in an excel worksheet: As you can see this comes out valid but in reality it isn't valid ...
4
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4answers
1k 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 ...
4
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2answers
362 views

Is Vallicella's argument that the future tense cannot generate the Liar paradox valid?

The Pinocchio paradox arises when Pinocchio says: "My nose grows" From Wikipedia, Pinocchio is known for having a short nose that becomes longer when he is under stress, especially while telling a ...
4
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4answers
315 views

Does this philosophical argument about accidents and universal origin contain valid logical structure?

I'm not enough of a philosopher to properly analyze this particular argument, but I'm curious about it and I'd like to see it dissected and explained. "If the solar system was brought about by an ...
4
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4answers
285 views

Reverse Conclusion of Hypothetical Syllogism

I am presented with an argument of form: If p, then q. If q, then r. Therefore, if r, then p. Does this structure have a specific title? I know that it is invalid, and am assuming that "reverse ...
4
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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 ...
3
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4answers
3k views

Is “(1) All humans are mortal. (2) Socrates is mortal. Conclusion: Socrates is human.” unsound argument?

I am new to a philosophy course and recently learned about validity and soundness of an argument. In this exercise: Premise 1: All humans are mortal. Premise 2: Socrates is mortal. ...
3
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5answers
496 views

valid or invalid: “S or R. Not S and Not R. Ergo, B.”

“Either it is sunny or it is raining. But now, it is neither sunny nor is it raining. So, the Boston Bruins will win the Stanley Cup this year.” Is this argument valid or invalid? I’m pretty stumped, ...
3
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3answers
307 views

Analogy between an unknown in an argument, and a contradiction in the principle of explosion

Context I like to argue that, since we do not know what consciousness is, we can not specify what it can not do. Therefore we can not state we can't do something now, nor in the future. Up to the ...
3
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6answers
8k views

How can one measure the quality of art?

In art (music, painting, etc.), is it meaningful to say that this piece is better than this one? I can understand somebody saying "I have more feelings, I'm more touched when I listen to this song ...
3
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4answers
208 views

Why are some communication failures regarded as important opinions in philosophy?

As a newbie here (though not on SO or on the net before that) I am surprised at the number of questions about what some philosopher meant. Examples, just picked from the time point of writing this ...
3
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5answers
1k views

Could the assumption of materialism be a flaw in the scientific method?

The scientific method operates by validating theories through observation and experimentation, if the observations and experimentation is inconsistent with the theory, the theory must be rethought. ...
3
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4answers
1k views

How to point out argumentation fallacy in “real life”

I often come up discussing (peacefully!) with people on a wide spectrum of topics, and equally often I have to debunk flawed arguments, in logic sense (see for example this question). However I can't ...
3
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5answers
1k views

Are all fallacious arguments invalid?

Is it possible for an argument that contains a fallacy to be valid? I have been told that fallacious arguments by definition are invalid. Is this true? Thanks!
3
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2answers
495 views

Argument where premises cannot all be true

Is an argument whose premises logically cannot be true at the same time a valid one? It seems it would be "vacuously" valid but I'm not sure about the precise definitions. Ie, is the following a ...
3
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2answers
240 views

Is this lexical or structural ambiguity: “criminal actions are illegal, and murder trials are criminal actions, so murder trials are illegal”?

I am yet to learn about ambiguity and sound arguments but am attepting to make the following argument sound. All criminal actions are illegal All murder trials are criminal actions Therefore All ...
3
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3answers
149 views

Concerning the definition of “valid”

I studying graduate math (not very far into it) and I realized that some of the higher level math texts I would like to read are hard to access without a strong basis in logic. Now I've taken ...
2
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7answers
2k views

Is the logic of this argument valid?

If God exists, it is rational for people to believe he exists without relying on facts: If God exists and he wanted to be known by people he would provide a means of knowing him. If God wanted as ...
2
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5answers
288 views

Question regarding sound argument [duplicate]

Sound argument is an argument which is both valid and it's premises are true. But my question is, why do we mention in the definition of the sound argument that "it's premises are true" when we've ...
2
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3answers
429 views

Is this argument about abortion being both right and wrong valid or invalid?

Abortion is either right or wrong. If it is right, then people should be allowed to kill fetuses. Killing fetuses is wrong. Hence, abortion is not right. If it is wrong, then women won’t have the ...
2
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1answer
2k views

soundness: how can one decide\know if premise is true or false

So I happened to read this article on wikipedia about soundness and there is this example of sound argument: An argument is sound if and only if The argument is valid. All of its ...
2
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3answers
78 views

Why is there an O type conclusion in modus celaront

Modus celaront is type logical syllogism. No reptiles have fur. (MeP) All snakes are reptiles. (SaM) ∴ Some snakes have no fur. (SoP) The conclusion is of a O type(Some .. are not ...). Why is ...
2
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3answers
447 views

Can p and q in modus tollens be stated negatively?

In a youtube video a commentator summarizes Andrew Klavan's argument as the following: If God does not exist, there are no objective moral values. There are objective moral values. God exists. The ...
2
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2answers
557 views

Contradictory Conclusions - Both cannot be valid

Q: Consider the following two propositions: Oswald shot Kennedy; Oswald did not shoot Kennedy. Suppose that we have two pieces of reasoning, one with the first as conclusion and the other with the ...
2
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2answers
101 views

Are valid arguments content blind?

Piggy backing off of this post here I want to make sure I understand this point clearly. Are valid arguments content blind? Even if the conclusions they make contradict? For example, the following ...
2
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1answer
181 views

Question about validity of Modus Tollens vs. Denying the Antecedent

I have no idea why (2) is an invalid argument. (1) If A, then B Not B Therefore not A (2) If A, then B Not A Therefore not B
2
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3answers
1k views

In basic logic, if an argument contains a self-contradictory premise, how come the argument is valid?

I have started to attend the logic lectures. The lecture notes indicate that a "self-contradiction" is a statement that is always false. But why will it lead to a valid statement?
2
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1answer
334 views

Soundness of a deductive argument

I am a student who was just introduced to philosophy. On a test, we were given the following multiple-choice question on soundness of a deductive argument: “Anything that travels in time necessarily ...
2
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1answer
49 views

Changing inconsistent to valid

I found the following passage in Mark Sainsbury's 'Logical Forms' If a collection of propositions is inconsistent, any argument whose premises consist of all but one of the collection, and whose ...
2
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1answer
676 views

Suppose the conclusion of an argument is logically equivalent to the conjunction of all the argument’s premises

Suppose the conclusion of an argument is logically equivalent to the conjunction of all the argument’s premises (the conjunction of all the arguments premises is just the statement obtained by taking ...
2
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2answers
114 views

‘The claim that I had an affair with Miss A and that I didn’t father her child is false’

The prosecutor asks, ‘Did you father the child of the murdered victim Miss A?’. Mr. N replies, ‘The claim that I had an affair with Miss A and that I didn’t father her child is false’. In response ...
2
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2answers
52 views

Is it possible to define argument validity as a formula?

Let A, B and C be propositions. Define ARG(A, B, C) as the following argument: A. B. Therefore, C. My goal is to create a formula whose truth value is equivalent to "ARG(A, B, C) is ...
2
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3answers
915 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 ...
2
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1answer
136 views

Tautologies and Quantification

Are the following two questions a) tautologically valid, b) logically valid but not tautologically valid, or c) invalid. Here's what I have so far: For 10.3: It is not tautologically valid since the ...
2
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0answers
1k views

Testing the validity of syllogism argument

I came across a validation method for testing the validity of a syllogistic argument which seems quite easier to grasp: For example: To test the argument: no P is B some C is B Therefore, some ...
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2answers
5k views

Is the following statement true, false, or can't be determined? Why?

"If it snows and we don't have school, then (x^3)<0 implies x is negative" (Assume x is a real number).
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3answers
5k views

Suppose you know the premises of an argument are inconsistent. Do you have to do a truth table to know whether it is valid or invalid?

Suppose you know the premises of an argument are inconsistent. Do you have to do a truth table to know whether it is valid or invalid?
1
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3answers
119 views

Is this argument about “either or” valid or invalid?

Unless something weird has occurred, either the basketball game is cancelled, the football game is cancelled, or Churchill never entered Switzerland. If any game is cancelled, then something weird has ...
1
vote
1answer
187 views

Validity and Soundness

The following is an argument which I thought was sound but I have been told I am wrong. Some men are married Therefore Some men are not married I think this argument is sound because the premise ...