This suggests that most of the methodological work in modern linguistics is not to be considered in determining the extended c-command discussed in connection with (34). It must be emphasized, once again, that the fundamental error of regarding functional notions as categorial is necessary to impose an interpretation on a general convention regarding the forms of the grammar. On our assumptions, the earlier discussion of deviance suffices to account for a stipulation to place the constructions into these various categories. However, this assumption is not correct, since the notion of level of grammaticalness is to be regarded as the requirement that branching is not tolerated within the dominance scope of a complex symbol. I suggested that these results would follow from the assumption that a case of semigrammaticalness of a different sort may remedy and, at the same time, eliminate nondistinctness in the sense of distinctive feature theory.
see also: WikiPedia -- Chomskybot