Why 'regret' and 'realize' can embed false beliefs

Verbs of emotion (e.g., regret) and discovery (e.g., realize) presuppose factivity, but they can felicitously follow false-belief statements that suspend their factivity (Klein, 1975; Gazdar, 1979), in contrast to know. This paper addresses this puzzle by proposing a believe-based account with two ingredients: (i) a lexical semantics of regret and realize that contains a backgrounding operator turning at-issue meanings into presuppositions, and (ii) a theory of presupposition projection in attitude contexts (Karttunen, 1974; Heim, 1992; Sudo, 2014). The factivity of regret and realize is derived as a context-sensitive pragmatic implicature, while the factivity of know is a lexical presupposition that holds across contexts.