A verb is transitive if it takes a direct object and intensional if it exhibits one or more intensionality effects in its direct object. The three main such effects are (i) resistance to interchange of coextensive expressions, such as coreferential names or common nouns that happen to apply to exactly the same objects; (ii) lack of existence entailments even when the direct object is existentially quantified; and (iii) a relational-notional ambiguity if the direct object is quantified.

Verbs of search, desire, and expectation, exhibit all three intensionality effects. Thus, for (i), "Lois seeks Superman" and "Lois seeks Clark" might differ in truth-value even though Superman is Clark. For (ii), "Perseus seeks a gorgon" can be true even if there are no gorgons (contrast the extensional transitive found). For (iii), "Richard III seeks a horse" is normally understood to mean that his search may be...