Suppose, for instance, that 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 fundamental error of regarding functional notions as categorial is, apparently, determined by the levels of acceptability from fairly high (eg (99a)) to virtual gibberish (eg (98d)). Summarizing, then, we assume that the notion of level of grammaticalness raises serious doubts about a corpus of utterance tokens upon which conformity has been defined by the paired utterance test. Conversely, a case of semigrammaticalness of a different sort is necessary to impose an interpretation on the extended c-command discussed in connection with (34). We have already seen that the systematic use of complex symbols is not quite equivalent to the ultimate standard that determines the accuracy of any proposed grammar.
see also: WikiPedia -- Chomskybot