It is a standard assumption of government-binding theory that the relationship between a constituent displaced by the transformational rule schema Move α and its trace is subject to the locality condition known as subjacency, the central principle of the subtheory of universal grammar known as bounding theory (Chomsky, 1981, 1982, 1986). Subjacency requires that not more than one ‘barrier’ intervene between a moved constituent and its trace, but the definition of the relevant barriers has been, and remains, an issue of considerable controversy. In Chomsky (1977) it is suggested that NP and one of S or S¯ are the ‘bounding nodes’ for English, and many standard textbooks have since argued for NP and S (e.g. Radford, 1981: Ch. 7; van Riemsdijk & Williams, 1986: Ch. 4). Nevertheless, the possibility of cross-linguistic parametric variation may have to be allowed for, since Rizzi (1978) makes out a case for S¯ rather than S as the clausal bounding node for Italian in order to account for the freedom of extraction from so-called ‘wh-islands’ in that language. Chomsky (1980), however, puts forward the possibility that S¯ may be a bounding node universally, and that languages vary according to whether S is also. If it is, then there will be no long-distance movement (cf. standard German and Russian) unless individual verbs are specified in the lexicon as ‘bridges’ which nullify the barrierhood of S¯ (cf. the majority of verbs subcategorized by clausal complements in English). This view is revised and refined in Chomsky (1981: 307), where S¯ is taken to be a bounding node universally when it includes a complementizer or wh-phrase preceding a finite clause, in which case the finite clause S may also optionally be a barrier, and S is taken to be a bounding node when it is governed, as is the case after S¯-deletion in the complements of ‘raising’ predicates. Finally, Chomsky (1986) seeks to unite the definition of barrier for the purposes both of movement and government, assuming two barriers block movement and one barrier blocks government, by proposing that any ungoverned maximal projection is a barrier, and that any maximal projection immediately dominating such a barrier, whether lexically governed or not, is also a barrier by inheritance.