Suppose, for instance, that this selectionally introduced contextual feature raises serious doubts about the extended c-command discussed in connection with (34). Thus most of the methodological work in modern linguistics does not readily tolerate nondistinctness in the sense of distinctive feature theory. To characterize a linguistic level L, the appearance of parasitic gaps in domains relatively inaccessible to ordinary extraction is not to be considered in determining a general convention regarding the forms of the grammar. On our assumptions, the earlier discussion of deviance is unspecified with respect to a stipulation to place the constructions into these various categories. For one thing, the notion of level of grammaticalness is necessary to impose an interpretation on an important distinction in language use.
see also: WikiPedia -- Chomskybot