 All three of these paths have been subsequently explored. Path (1) appealed to generative Essentialists. Chomsky (1981) suggested an extreme restriction: that universal grammar permitted only finitely many grammars. This claim (for which Chomsky had little basis: see Pullum 1983) would immediately guarantee that not all finite languages are humanly learnable (there are infinitely many finite languages, so for most of them there would be no permissible grammar). Osherson and Weinstein (1984) even proved that under three fairly plausible assumptions about the conditions on learning, finiteness of the class of languages is necessary—that is, a class must be finite if it is to be identifiable from text. However, they also proved that this is not sufficient: there are very small finite classes of languages that are not identifiable from text, so it is logically possible for text-identification to be impossible even given only a finite number of languages (grammars). These two results show that Chomsky’s approach cannot be the whole answer.