If (7) is not self-contra- dictory, then the negation of (7a) does not necessitate (7b) in the strong sense required for semantic presupposition. (7a)'s negation does conversationally implicate (7b), by way of the Maxim of Strength; someone who utters "It was not Grannie who robbed the diaper service" is in a position to make a stronger and more usefully informative denial, namely that of (7b) itself. But conversational implicature is cancelable, as necessitation is not. No necessita- tion, no semantic presupposition. (8), though interrogative, meets a similar fate. If you are married and you are asked (8) (and you have never beaten your spouse), here is the correct answer: "No."6 Because one can stop doing a thing only if one has at some time been doing it. (Of course the answer "No" is misleading because, via the Maxim of Strength, it implicates that one has beaten one's spouse and continues to do so. The correct and nonmisleading answer would be, "No,
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