Questions tagged [validity]

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Question of Validity in syllogisms of deductive argument

I read the following excerpt from my A-Level Philosophy book: "Two key terms that you need to understand in relation to deductions and other forms of argument are ‘validity’ and ‘soundness’. ...
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Valid or invalid? ( from a CSU Exam, instructor Tim Black)

Source : http://www.csun.edu/~tab2595/PRAC_EXAM_1.pdf Is the following argument valid or invalid? (1) No email messages are written carefully, (2) but every love letter is very carefully written. ( ...
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How can we prove this argument is invalid?

Let's say below is the argument, Premise 1: All men are mortal Premise 2: Socrates is a man ------------------------------------------ Conclusion: Therefore, Socrates can think Now, to prove an ...
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Is it a valid argument?

I wonder if the below argument is a valid or invalid? Premise 1: All the humans can fly Premise 2: I am a human --------------------------------- Conclusion: Therefore, I can fly I also wonder, if ...
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Is it true that if an argument is invalid, any argument of that logical form must be invalid?

I am stuck over whether these statements are true: First: "If an argument is invalid, any argument of that logical form must be invalid." Second: "There may be invalid argument with ...
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can an argument containing a contradiction be valid argument

I know that validity has nothing with truth of the conclusion or with how good argument is in general, and an argument is valid iff the truth of its premises guarantees the truth of its conclusion. ...
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Are there multiple definitions of validity?

I have recently started learning the basics of propositional logic. According to http://intrologic.stanford.edu/chapters/chapter_03.html, a sentence is valid if and only if it is satisfied by every ...
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Counterfactuals in Premises for Arguments

Can counterfactuals in premises make an argument sound and valid? I understand that soundness requires both validity and true premises whilst validity requires the premises to follow to the conclusion....
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In logic, can we or can we not prove that a formula is invalid?

I'm a novice in this field of logic. While reading about soundness and completeness of a method, I read this line: "a logical system has the soundness property if and only if every formula that ...
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Where is the fallacy in Seth Yalcin's counterexample to the modus tollens?

Where is the fallacy, do you think, in Seth Yalcin’s argument (2012) that the Modus Tollens is not a generally valid form of argument? Seth Yalcin’s counterexample to the Modus Tollens (MT) https://...
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Modal Logic: Proving Schema Validity

When faced with a question of the sort, "Is schema X valid in class of frames C?", we usually go about proving or disproving this by assuming the antecedent of X and showing that the consequent ...
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Is this an argument by simplification: it can be done by doing Y, therefore it can be done?

The problem is X This problem can be easily solved by doing Y Therefore this problem can be easily solved I am confused if this is Simplification (Which means the inference is Valid)
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Modal Logic: Why are Universal frames a subset of Equivalence frames?

I'm looking through the lecture notes for my course on modal logic and am having a hard time understanding why it is that U, the class of all Universal frames, is a subset of E, the class of all ...
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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 ...
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What is an argument with necessarily true conclusion?

I cannot understand what an argument is with a necessarily true conclusion. Could you explain to me what it is and write here some examples? Moreover, what is the meaning of “necessarily true” and “...
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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 ...
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2answers
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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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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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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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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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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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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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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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‘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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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. Conclusion: ...
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2answers
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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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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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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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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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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 ...
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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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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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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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What is the nature of “validity” in deduction when dealing with conclusions unrelated to premises?

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 understand without a strong basis in logic. Now I've taken ...
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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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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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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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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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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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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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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: &...
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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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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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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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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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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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Can an Argument be ever a hypothesis? [closed]

Can I have an argument which can be a hypothesis?
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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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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. ...