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# Questions tagged [validity]

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### 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 ...
434 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....
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 ...
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 ...
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 ...
1k views

### Determining the soundness of arguments

I was recently given the following question in an exam. Determine the soundness of the following argument: John lives on the same street as Mary. Mary lives on the same street as Sam. ...
4k 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?
130 views

### Suppose the conclusion of an argument is known to be tautologous. Do you have to do a truth table to know whether it is valid or invalid?

Suppose the conclusion of an argument is known to be tautologous. Do you have to do a truth table to know whether it is valid or invalid?
668 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 ...
60 views

### Is it possible to determine the soundness of the following argument?

I have over-analysed the following question and now find myself thoroughly confused. I think my issue lies with the use of the word 'some' which we are asked to assume means 'an indeterminate number ...
555 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 ...
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 ...
5k 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?
905 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 ...
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 ...
286 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 ...
260 views

### Proof validity methods other than truth tables

I have read or heard some time ago that truth tables cannot be used to validate arguments which involves the use of quantifiers i.e. in predicate or quantificational logic where you can find ...
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 ...
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 ...
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. ...
658 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'...
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 ...
42k 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 ...
494 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 ...
962 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 ...
2k views

### Valid and invalid arguments [closed]

I have an assignment that asks: Can an argument have false premises and a false conclusion and still be valid? false prem and a true conclusion? true prem and a true conclusion? true prem and a false ...
209 views

### formula which is k-valid for only k > 2

I need to find a formula, which is satisfiable in all interpretations of a domain with k>2 elements, but shouldn't be satisfiable in any domains with k≤2 elements. As I understand it, that means that ...
131 views

### Structural understanding vs. emotional connection [closed]

Question: Is there a line of philosophical thought or a named theory/area-of-inquiry that deals with the phenomenon of a person perceiving/believing that appreciation for an event/topic/item decreases ...