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Questions tagged [validity]

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Is this argument about ownership valid?

I came across an argument that I believe to be invalid: Ownership is defined as the ability to exclude others. "Everyone owns land" becomes "everyone has the ability to exclude others from land." I ...
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2answers
3k 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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2answers
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I need some help determining the validity of the following argument

“I got the highest grade on the last test and I have perfect attendance. If I get a cold, then I miss at least one class. I came down with a cold. Therefore, if I missed at least one class, then I ...
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3answers
94 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 ...
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5answers
454 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, ...
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3answers
233 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 ...
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3answers
149 views

Arguments/premises to disprove God's omniscience

I was thinking about validity of God's omniscience and stumbled upon three statements, which can be summarized as - To be omniscient, a being would require to capture and store all the data in the ...
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0answers
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‘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 ...
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4answers
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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. ...
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2answers
36 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 ...
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5answers
699 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!
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2answers
166 views

How do I prove: 1. A v (B & C) 2. (A v C) > ~(G & O) / ~G v ~O

This is a question for my philosophy. Prove this valid using any of the rules we've studied so far: A v (B & C) (A v C) > ~(G & O) / ~G v ~O
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10answers
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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? ...
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1answer
59 views

Can a priori reconsideration improve on a priori theory? “Analytical” etc. schools

So something strange I've realized lately, in the humanities and social sciences it's fairly common to see labels such as "analytical", "analytic school" etc. which I read to suggest as if these ...
2
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1answer
149 views

Why is Truth the default designated value in logic and language?

It seems that investigations of language and logic have focused on truth as the assumed designated value (the value preserved by valid entailments). It is only in later, non-classical logic that non-...
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1answer
49 views

Are these basic arguments considered valid and sound?

I'm trying to come up with some basic arguments to construct a philosophy paper and I am wondering if the following arguments are valid and sound. Thanks for the help! If humans have flaws then they ...
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5answers
159 views

Is university research a guarantee for accuracy of theory?

Is university research a guarantee for accuracy of theory? I think and speculate that no and on the contrary the "status" of academic degrees and university relationships are used to "validate" even ...
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2answers
104 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 ...
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3answers
1k 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 ...
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3answers
662 views

Determine if an argument is valid or invalid

The following is an argument. Is it valid ? Abortion is not wrong, because women have a right to control their bodies. The following is also an argument. Is it valid ? All students love ...
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1answer
158 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
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2answers
96 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 ...
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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 ...
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3answers
855 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?
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4answers
214 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 ...
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0answers
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What are the Limitations and Vulnerabilities of Objectivity Biases?

How reliable is a "Logic / Objectivity" Bias when it comes to reasoning? Or, What are the potential limitations or vulnerabilities of relying solely on these bases of reasoning? Note 1: "Objectivity"...
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3answers
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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 ...
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5answers
2k views

Can you make a valid inference invalid by adding extra premises?

From An introduction to formal logic by Peter Smith there is a question: Can you make a valid inference invalid by adding extra premises? I think it's true. If I add premises that contradict ...
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1answer
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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 ...
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1answer
298 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 ...
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1answer
469 views

Is it valid to prove the axioms of a system from themselves? How does it square with Gödel's incompleteness?

I recently asked whether the axioms are tautologies, and got comments that seemed to me highly suspicious. Namely, that you can always prove an axiom from itself, that you can trivially say A ...
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1answer
128 views

Can an Argument be ever a hypothesis? [closed]

Can I have an argument which can be a hypothesis?
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3answers
302 views

Logical analysis of “Free will and god(s)” argument

Please evaluate the following argument strictly for formal logical validity. I am NOT interested in debating the content or in philosophical perspectives on the content. However, I AM interested in ...
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0answers
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What is a faster method other than truth tables for validating a sentence?

I've learned how to do truth tables with the different syntaxes (conjunction, disjunction, etc.), but when it comes to 3-5 atomic sentences it takes too long to do a full truth table with 8-32 lines. ...
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0answers
132 views

In the context of debate centred on a statement, how to validate arguments given to confirm or disconfirm that statement in a logical manner?

Let's say we have the following statement to serve as a starting point around which a debate can be centerd. Man is immortal Someone could say that man is mortal according to accepted scientific ...
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2answers
39 views

Not sure if my logical equivalences are correct here or not

I have a problem here that I'm trying to solve. The question asks me to check whether the argument is valid or not without using a truth table. I used equivalence laws to reduce the statement down ...
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1answer
92 views

How to infer ¬Q when there seems to be no way to

Rule #1: No man shall hit another man. Rule #2: If someone breaks Rule #1, then Rule #1 does not apply to such a one. My specific question is: How can someone infer that Rule #1 does apply to him? ...
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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 ...
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4answers
306 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 ...
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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 ...
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1answer
160 views

Why must the sentence form of a valid argument be tautological? [closed]

I was thinking along the lines of the obvious, such as when found tautological the form must have been valid but I'm sure there is a more in-depth explanation that I can't reach.
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2answers
277 views

Can an argument be valid if one of its premises is invalid?

I know that an argument's validity has nothing to do with the truth of its premises, but does it have something to do with the validity of its premises? I'm thinking specifically of where a premise is ...
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4answers
941 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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6answers
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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 ...
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3answers
641 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 ...
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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 ...
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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....
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4answers
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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 ...
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1answer
156 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 ...
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2answers
227 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 ...