Suppose, for instance, that the theory of syntactic features developed earlier appears to correlate rather closely with problems of phonemic and morphological analysis. Comparing these examples with their parasitic gap counterparts in (96) and (97), we see that the notion of level of grammaticalness delimits an important distinction in language use. Of course, this selectionally introduced contextual feature cannot be arbitrary in irrelevant intervening contexts in selectional rules. However, this assumption is not correct, since the fundamental error of regarding functional notions as categorial is not subject to a descriptive fact. Let us continue to suppose that the speaker-hearer's linguistic intuition is necessary to impose an interpretation on a general convention regarding the forms of the grammar.
see also: WikiPedia -- Chomskybot