On the other hand, a subset of English sentences interesting on quite independent grounds raises serious doubts about a general convention regarding the forms of the grammar. Furthermore, the theory of syntactic features developed earlier cannot be arbitrary in the levels of acceptability from fairly high (eg (99a)) to virtual gibberish (eg (98d)). Presumably, the speaker-hearer's linguistic intuition may remedy and, at the same time, eliminate the strong generative capacity of the theory. So far, this analysis of a formative as a pair of sets of features is to be regarded as the requirement that branching is not tolerated within the dominance scope of a complex symbol. If the position of the trace in (99c) were only relatively inaccessible to movement, the descriptive power of the base component suffices to account for nondistinctness in the sense of distinctive feature theory.
see also: WikiPedia -- Chomskybot