Therefore it does seem relavant to talk about the distinction between soundness and validity in the articles for MT and MP. "But", Socrates argues, "I consider the Sun to be firy." (which would invalidate the first premise). (A) If there is fire there, then there is oxygen there. Just as 217.* mentioned, there are assumptions in the two arguments which are not necessarily agreed upon by all parties: However we find in much popular rhetoric that this is not always the case. (C) Therefore, P is false, OR (A) is unsound, or (B) is unsound.Įssentially, for me to agree (C), I must agree (A,B). It doesn't take an expert to see that, just someone who is willing to spend some time learning.
Denying the 'if-then' results in a valid argument that ~p. That is, in this case, denying the premise is denying (r>s). Now, (p>q) is one premise of the argument, ~q is the other. Yes, don't discuss it, leave it to the "expert". I'll leave you to your "domain", wise-guy.
But the priggish remarks have made me puke. I don't mind too much if you are an idiot. Banno 22:43, (UTC) So denying a "premise" is the same that denying an if-then statement ? And you think you know about the topic ? You are only a wiseacre. Please have the curtesy to restrict your edits to topics of which you have some knowledge. I assume that by 'premisse' you mean 'Premise'? If so, then certainly, provided the conditional is a premise of the argument. So for you, denying a premisse or denying an "if-then" statement is the same thing ?ĭo you really believe that denying a "if-then" statement still allows any "validity" or any meaning at all whatsoever ? Which is something completely different to which the validity notion does not apply. You are denying a if fact A then Fact B connection. In the example in this article you do something completely different Or perhaps you are confused? Denying "If Lizzy was the murderer, then she owns an axe" is something completely different from denying the sentence "All dogs have eight legs" in the example given in the article Validity Read this article and take the quiz to make sure you understand the difference between validity and soundness. The problem appears to be with 217.228.220.2?s understanding of these terms rather than with the argument. The example is of a valid argument that contains a false premise, and therefore a false conclusion. 217.228.212.196 12:06, (UTC)ĭoes every article on logic have to carefully explain the distinction between falsehood and validity? This simple point keeps recurring. But it certainly doesn't have anything to do with the fact that roses are red or not.
Lizzy may be the murder or not, we don't know that. It has the same meaning than saying: If roses are red, then Lizzy is the murder. If the premise is false, the whole argument is not only invalid, it loses any meaning. Who cares if Lizzy owns an axe or not ? It is irrelevant. An argument can be valid even though it has a false premise one has to distinguish between validity and soundness." "This may mean that the argument is false, but notice that it does not mean the argument is invalid. If there is no connection between the ownership of an axe and guilt in this crime, then who cares if Lizzy owns an axe or not ? It is irrelevant. If we cannot assume that there is a connection between the ownership of an axe and guilt in this crime, than we can't make any judgements at all, can we ? "That might be a legitimate criticism of the argument, but notice that it does not mean the argument is invalid. This seems a strange set of onward links as MT is not a common phrase in everyday language comparable to non-sequitur and is more appropriately linked with philosophical, linguistic or mathematics in my view. 11 Is Modus Tollens really the formal name for proof by contraposition?.
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