 Within an epistemic logic setting, one may represent the communicative situation of an utterance with presuppositions as follows. First, we need to represent what a speaker assumes about what her audience knows or believes in a multi-agent belief (or knowledge) state, then we need to model the effect of the communicative action on the belief state. A simple way to handle presupposing utterances in dynamic epistemic logic is by modeling a presupposition \(P\) as a public announcement “it is common knowledge that \(P\)”. In cases where it is indeed common knowledge that \(P\), an update with this information changes nothing. In cases where \(P\) is not common knowledge, however, the utterance is false, and public announcements of falsehoods yield an inconsistent knowledge state.