Syntactic ergativity as absolutive movement in Tongic Polynesian

We propose a unified account of the presence of syntactic ergativity and the availability of variable post-verbal word order in the Tongic branch of Polynesian languages. In Tongan, ergative subjects cannot freely extract, and both VSO and VOS word orders are possible. By contrast, ergative subjects in Niuean freely extract, but word order with two full DP arguments is strictly VSO. We argue that these differences stem from a single point of parametric variation in the syntax: the locus of absolutive case assignment (Bittner & Hale 1996; a.o.). In Tongan, absolutive is assigned by T0, such that the object must A-move past the ergative subject, giving rise to extraction restrictions and the availability of VOS word order. In Niuean, absolutive is assigned by v 0; as such, there is no object A-movement, hence no extraction restrictions, and VOS is not possible.