Note that the descriptive power of the base component is not quite equivalent to a corpus of utterance tokens upon which conformity has been defined by the paired utterance test. Thus most of the methodological work in modern linguistics is to be regarded as irrelevant intervening contexts in selectional rules. For one thing, relational information may remedy and, at the same time, eliminate the traditional practice of grammarians. Let us continue to suppose that this selectionally introduced contextual feature is, apparently, determined by the system of base rules exclusive of the lexicon. To characterize a linguistic level L, the earlier discussion of deviance appears to correlate rather closely with problems of phonemic and morphological analysis.
see also: WikiPedia -- Chomskybot