In this paper I elaborate on previous criticisms of the influential Stalnakerian account of presuppositions, pointing out that the well-known practice of informative presupposition puts heavy strain on Stalnaker's pragmatic characterization of the phenomenon of presupposition, in particular of the triggering of presuppositions. Stalnaker has replied to previous criticisms by relying on the well-taken point that we should take into account the time at which presupposition-requirements are to be computed. In defense of a different, 'semantic' (in a sense) account of the phenomenon of presupposition, I argue that that point does not suffice to rescue the Stalnakerian proposal, and I portray Lewisian 'accommodation' as one way in which speakers adjust themselves to one another in the course of conversation.