Originally posted by no1marauderAnswer the question. Can we use "or" and "not" in everyday use as logicians do, or do we have to avoid those as we do implications?
Again, there is a thing called a paragraph. The sentences in this thing are supposed to stand together and present a coherent idea. Your's didn't.
Originally posted by DoctorScribblesLMAO! I don't take orders from you; your question is BS.
Answer the question. Can we use "or" and "not" in everyday use as logicians do, or do we have to avoid those as we do implications?
In normal discourse, if you deny the possibility of the condition precedent than there is little sense in discussing the ramifications of the impossible thing occurring. See my rain on the Moon example. While such intellectual jacking off might pass a small amount of idle time (say between passing a joint) and/or might impress particularly naive female undergrads, it's a poor way of trying to communicate an idea (assuming you actually had a coherent one, which seems unlikely).
Originally posted by no1marauderI think you're scared to give a response, either because you are generally afraid of my expertise, or because you know enough about the relationship between logical operators to understand exactly why I am asking this particular question.
LMAO! I don't take orders from you; your question is BS.
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Originally posted by DoctorScribblesNo. Yes.
Do you generally deny that proof by contradiction is a sound method of argument? Do you even recognize the method in action when you encounter it?
Proof by contradiction assumes that the proposition is untrue, not true and is used to prove the truth of the proposition, not its falsity. Brush up. http://mathworld.wolfram.com/ProofbyContradiction.html
Thanks for your "expertise".
Originally posted by DoctorScribblesFirst your admission that you didn't know what proof by contradiction actually was would be required (and amusing).
Do you mean to say that useful reasoning can proceed from false premises after all?
Weren't you just criticizing me for investigating the entailments of a false premise?
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Originally posted by no1marauderLOL. Funniest thing I've read all day, even better than the imagination competition.
First your admission that you didn't know what proof by contradiction actually was would be required (and amusing).
Do you think it's just a coincidence that I asked you if you recognized it, and after you looked up its definition it turned out to be exactly the method I employed, and moreover, that your reference indicates that it is a sound method of argument, contrary to your insistence that it is useless to investigate the entailments of false premises? It must be my lucky day.
Originally posted by no1marauderHe does know what he is talking about. Proof by contradiction takes the form of a conditional proof with the consequent being a contradiction (from which the negation of the antecedent can then be inferred), and is a valid mode of inference precisely because the truth conditions for the logical operator "if, then" are as earlier described (i.e., as per the material conditional).
First your admission that you didn't know what proof by contradiction actually was would be required (and amusing).
Originally posted by DoctorScribblesYour full of crap level is at an all-time high.
LOL. Funniest thing I've read all day, even better than the imagination competition.
Do you think it's just a coincidence that I asked you if you recognized it, and after you looked up its definition it turned out to be exactly the method I employed, and moreover, that your reference indicates that it is a sound method of argument, contrary to y ...[text shortened]... that it is useless to investigate the entailments of false premises? It must be my lucky day.
It most certainly wasn't the "method" you employed as already explained.
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Originally posted by bbarrSince his first post assumed the proposition was true, not untrue, he wasn't using proof by contradiction.
He does know what he is talking about. Proof by contradiction takes the form of a conditional proof with the consequent being a contradiction (from which the negation of the antecedent can then be inferred), and is a valid mode of inference precisely because the truth conditions for the logical operator "if, then" are as earlier described (i.e., as per the material conditional).
EDIT: Anyway, the question was whether question 3 was true in any meaningful sense if the answer to question 2 is false. So this is just the intellectual jacking off I already referred to.
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Originally posted by no1marauderLMAO! You are one confused old man.
Since his first post assumed the proposition was true, not untrue, he wasn't using proof by contradiction.
What is the proposition in question that you assert I assumed to be true?
Don't you realize assuming one proposition is true is equivalent to assuming that its negation is false? I suggest you carefully label all of the propositions in question, and you will see that, wonder of all wonders, it fits the mold as described in your reference.
Originally posted by no1marauderIt doesn't matter if you assume that a proposition is true. If you assume that P is true, and then go on to derive both P and ~P on the same line of a proof, you are thereby licensed to infer ~P. This would still be (literally) a textbook example of proof by contradiction.
Since his first post assumed the proposition was true, not untrue, he wasn't using proof by contradiction.
EDIT: Anyway, the question was whether question 3 was true in any meaningful sense if the answer to question 2 is false. So this is just the intellectual jacking off I already referred to.