It is proposed that sentential complements such as that S or whether S denote sentential quantifiers where a sentential quantifier is a set of sentential predicates (like is a rumour, is strongly believed) and a sentential predicate is a set of (declarative) sentences. Some properties of sentential predicates are studied and an analogy with nominal quantifiers is pointed out. An application to the analysis of questions (interrogative sentences) is made. Questions are rogative sentential predicates (which are semantically defined). No reference to possible worlds is made in the proposed analysis.