Current research on the syntax-semantics interface demonstrates the dramatic extent to which syntactic structures constitute transparent reflections of well-defined semantic regularities. As this paper shows, the empirical results accumulated within this framework strongly suggest that a theoretical distinction should be made between two distinct levels of meaning representation: A level of conceptual meaning on the one hand, and a uniquely linguistic level of meaning — Linguistic Semantics — on the other. The semantic notions and regularities which turn out to determine major syntactic phenomena are best interpreted as belonging to the level of Linguistic Semantics, rather than to the level of conceptual meaning. This view helps characterize language as a unique and functional system — a cognitive system whose function is defined at the level of Linguistic Semantics. It explains the fact, most recently highlighted by Levinson (1997), that the expressive power of language, as a tool for the communication of meanings, is constrained in non-trivial ways.