Presupposed information is information that is presented as given, and according to the so-called “binding theory” of presupposition this means that presuppositions want to have discourse referents to bind to (van der Sandt 1992, Geurts 1999).  However, whereas anaphoric pronouns are rarely interpretable in the absence of a suitable antecedent, the same does not hold for all presupposition-inducing expressions. For instance, a speaker may felicitously assert that he met “Pedro’s sister” even if he knows full well that his audience wasn’t aware that Pedro has a sister. In such cases, Karttunen (1974) and Stalnaker (1974) suggested, presuppositions are generally accommodated, which is to say that the hearer accepts the information as given, and revises his representation of the context accordingly. Accommodation, thus understood, is a form of exploitation in Grice’s sense: the purpose of presuppositional expressions is to signal that this or that information is given, and if some information is new but not particularly interesting or controversial (like the fact that somebody has a sister) the speaker may choose to “get it out of the way” by presuppositional means.