 The fact that presuppositions associated with unembedded triggers are not cancellable, except in an outright retraction of what the speaker has previously claimed, is one of the features that distinguishes most presuppositions from Gricean conversational implicatures (Grice, 1989). For example, an utterance of (11a) might ordinarily lead to the so-called scalar implicature in (11b). But while this implicature is cancellable, as in (11c), the presupposition that there is a knave, once again, is not cancellable, as shown by the oddity of (11d).