In this paper, we offer an argument in favor of the modular character of mind, based on a more detailed proof of the modular character of the linguistic capacity: in comparing the properties of different components of grammar in a specific area we will draw general consequences about the properties of the cognitive system. More specifically, we analyze and compare the properties, in logical form (LF)and in phonology, of “empty eIements” - eIements that are “visible” or “full” at some level (...) of representation, but not at another level.Our analysis shows that empty eIements are governed at LF by principIes on variables. binding conditions, and thematic principles, that relate eIements at a distance. In phonology, on the other hand, empty elements, i.e., empty segments and empty properties, can be obtaines by deletion and are governed by very different principles (underspecification, principles relating to recoverability of deletion effects), andthese principles relates eIements under strict adjacency. In addition, when a principle seems to be operating in a similar fashion in both components, as in the case of the Projection Principle, it involves lexical properties, which are properties affecting all components. We conclude, hence, that grammar is a modular system, with different components following different principles but related of course, among other things, by the properties of lexical structure.It follows from this analysis that a theory that views language as part of a homogeneous cognitive capacity cannot be mantained: cognition cannot be nonmodular in a strict sense, since a subpart of it, the linguistic capacity is modular itself. We conclude also that the linguistic capacity being modular, we ean only expect that, when studied in more detail, other cognitive capacities will be shown to differ intheir structure still more from the language system. (shrink)