Subset controllers in agreement relations

Agreement relations are interpreted asymmetrically, in that phi-features restrict the interpretation of the controller, but not the target, of the agreement relation. In this paper we explore whether this semantic asymmetry corresponds to a syntactic asymmetry. We will argue that it does not: phi-features are generated independently on target and controller. The evidence comes from cases of what we term 'subset control', in which the controller has fewer features than the target. We will argue that there are genuine cases of subset control that cannot be explained away, neither by assuming the controller contains non-realised features, nor by assuming that the underspecified category is not the actual controller, the latter being a fully specified null element. Our main evidence comes from Spanish 'unagreement'.