I examine the semantics of modal adjectives based on their selectional properties, arguing that they only combine with nouns describing situations or participants in situations (entities in context), and I propose a formal treatment. I attempt an extension of this analysis to temporal adjectives, thereby outlining a unitary treatment of non-subsective adjectives. The analysis involves the assumption, for nouns, of denotations and semantic types consistent with what they describe, and a revision of the denotations of intensional operators when used with nouns describing or involving situations.