Today's topic comes from an episode of Friends. One of the (male) characters is discussing a hypothetical situation and says "If I were a man..." and then trails off, the audience laughs, and he continues, "Did I just say 'If I were a man'?"
The intended sentence, of course, would have been, "If I were a man and X", where X is some hypothetical situation. This is an example of a counterfactual, where the protasis (the if clause) contains a hypothetical situation which is counter to fact. The sitcom character takes the counterfactual in his dialogue to be "If I were a man", i.e., "If X" where X = "I am a man". In fact, the counter to fact clause is "If I were a man and X", where X is the hypothetical situation in question. Since this is a counterfactual, we know that the protasis must be false, but the protasis is not "If X", but rather "If X and Y". While the opposite of X is ~X (where ~ is the negative quantifier), the opposite of (X and Y) is ~X or ~Y, not necessarily ~X and ~Y. Thus in the dialogue, the speaker can of course still be a man and say "If I were a man and Y". All this means is that one of the conditions be false, in this case presumably Y.
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