 This made it possible to capture, with precision, the idea that an inference is valid in the predicate calculus iff: every interpretation that makes the premises true also makes the conclusion true, holding fixed the interpretations of logical elements like ‘if’ and ‘every’. Davidson (1967a) conjectured that one could do for English what Tarski did for the predicate calculus; and Montague, similarly inspired by Tarski, showed how one could start dealing with predicates that have quantificational constituents. Still, many apparent objections to the conjecture remained. As noted at the end of  section four,  sentences like ‘Pat thinks that Hesperus is Phosphorus’ present difficulties; though Davidson (1968) offered an influential suggestion. Davidson’s (1967b) proposal concerning examples like (37–40) also proved enormously fruitful.