To characterize a linguistic level L, any associated supporting element is unspecified with respect to the ultimate standard that determines the accuracy of any proposed grammar. For one thing, a subset of English sentences interesting on quite independent grounds does not readily tolerate a descriptive fact. However, this assumption is not correct, since most of the methodological work in modern linguistics is not subject to a corpus of utterance tokens upon which conformity has been defined by the paired utterance test. Thus the descriptive power of the base component suffices to account for the system of base rules exclusive of the lexicon. A consequence of the approach just outlined is that the systematic use of complex symbols is not quite equivalent to an important distinction in language use.
see also: WikiPedia -- Chomskybot