Following a long tradition of studies on English auxiliaries and modals (Chomsky 1957), Burzio (1986) adopts a monoclausal analysis for auxiliary-past participle constructions, under which the participle is inserted in the lexical verb position V of the sentence, while the auxiliary is inserted in the functional I position. In such a perspective, auxiliary choice is to be thought of as a set of restrictions that the main verb V imposes on the its functional projection I. According to Burzio (1986), who takes up in this respect the analyses of relational grammar (Perlmutter 1978; cf. also La Fauci 1989), in standard Italian the auxiliary to be is associated with unaccusatives, while to have is associated with unergatives and transitives. In Burzio’s (1986) terms, unaccusatives have only an internal argument, while unergatives have only an external argument and transitives both an internal and an external argument. This distribution of thetaroles is paralleled by a distribution of cases whereby crucially unaccusatives do not assign accusative case. Therefore the argument of unaccusatives is forced to

move from its base-generated object position to the subject position. In this perspective the basic environment for the choice of the auxiliary to be is the one determined by movement from object into subject position, while the other environments are associated with to have. An interesting complication arises from the fact that si constructions are always associated with to be. In particular, according to Burzio (1986), reflexive and impersonal si require an extra rule to the effect that to be is chosen when there is a binding relation between the subject and the object, namely si. Needless to say, the disjunctive nature of the final rule represents a problem for the whole approach.