Phase in terms of Case

Chomsky (2000, 2001) proposed a phase model of syntax in which the phase forms a local domain for syntactic operations. What constitutes a phase is a semantic notion proposition rather than a syntactic property. This paper points out that viewing phases as propositional objects is conceptually inadequate in that a phase is defined in terms of a semantic notion proposition but not by a syntactic property and then discusses empirical deficiency with the proposition-based phase system. As an alternative, this paper suggests that phases be defined in terms of Case, the idea originally going back to Lee (1991, 1992) in which Case determines a barrier for syntactic operations, called Case Minimality. Natural consequences and wider empirical coverage of the proposed Case-based phase system confirm that Case is a crucial property in imposing syntactic locality.