Questions tagged [validity]
The validity tag has no usage guidance.
78
questions
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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 ...
2
votes
4answers
106 views
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 “...
3
votes
3answers
297 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 ...
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vote
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 ...
1
vote
2answers
4k 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).
1
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2answers
74 views
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 ...
1
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3answers
103 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 ...
3
votes
5answers
477 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, ...
2
votes
3answers
345 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 ...
1
vote
3answers
160 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 ...
2
votes
2answers
104 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 ...
3
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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.
...
2
votes
2answers
41 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 ...
3
votes
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!
1
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2answers
224 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
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?
...
1
vote
1answer
60 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 ...
1
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1answer
164 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-...
0
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1answer
52 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 ...
0
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5answers
165 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 ...
3
votes
3answers
138 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
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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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vote
3answers
811 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 ...
2
votes
1answer
171 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
votes
2answers
99 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
votes
3answers
396 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
votes
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?
4
votes
4answers
246 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 ...
0
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0answers
59 views
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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votes
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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vote
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 ...
2
votes
1answer
129 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
votes
1answer
313 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 ...
0
votes
1answer
486 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
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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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0answers
59 views
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. ...
0
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0answers
133 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 ...
1
vote
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 ...
1
vote
1answer
95 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?
...
2
votes
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 ...
4
votes
4answers
311 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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votes
5answers
747 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 ...
0
votes
1answer
161 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
300 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
999 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 ...
4
votes
4answers
670 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 ...
2
votes
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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votes
3answers
406 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....
