Humor. It is not a difficult concept. It is most logical.

"If A, then B" is true only if A is true and B is true. If A is true and B is false, then, "If A, then not B" except where A and B share no correlation. The country of which London is the capital is not relevant to the question of the gender of the speaker, which is why the quoted statement is not, in fact, logically valid.

The first and second sentences in the quote are unconnected claims; there is no progression of logic from one claim to the next. Therefore, there is no logic there. The third claim is connected to the second, but because it is deliberately vague, it carries no logical weight. It poses as a conclusion but has no premise.

Um. You're wrong on all four counts. I'm not sure where to go from here. If you like, you could take the last sequence, the one you call logically valid, and replace both instances of "humans" with "Arabs", thus arguing in a "logically valid" fashion and from true premisses that all American citizens are Arabs.

But we're way off track from the original point; I guess there is just no way the two of us will agree about a definition of the term 'humour' that uses the term 'logic', since we fundamentally disagree on the latter. Also, this thread was funnier a page back.

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