On negative yes/no questions

Preposed negation yes/no (yn)-questions like Doesn't John drink? necessarily carry the implicature that the speaker thinks John drinks, whereas non-preposed negation yn-questions like Does John not drink? do not necessarily trigger this implicature. Furthermore, preposed negation yn-questions have a reading 'double-checking' p and a reading 'double-checking' -->p, as in Isn't Jane coming too? and in Isn't Jane coming either? respectively. We present other yn-questions that raise parallel implicatures and argue that, in all the cases, the presence of an epistemic conversational operator VERUM derives the existence and content of the implicature as well as the pl-->p-ambiguity.