Two Places Where We Need Plug-Negation in Update Semantics: Symmetrical Presupposition Filtering and Exclusive Disjunction

This study investigates the projection problem of presuppositions, focusing on projection from disjunctions. I argue that we need what I call the plug-negation, the negation that filters presuppositions in two places. One is within the definition of disjunction that validates the symmetrical presupposition filtering effect [13], and the other is within the definition of exclusive disjunction. Without the plug-negation, a presupposition of a disjunct in those cases is wrongly predicted to project unconditionally, which would cause a violation of genuineness [22]. The violation is avoided with the plug-negation. I also propose that the appearance of the plug-negation is conditioned as a last-resort option.