Classic problems of how to generalize over predicate-argument relations (e.g., buy vs. sell; spray paint vs. spray a wall) have led to postulating semantic representations which are structured differently than deep syntax, such as (linked) theta grids and (lexical) conceptual structures. I argue that such autonomous semantics massively violates parsimony, and that theta-roles are better predicted by using only modestly enhanced, independently justified deep structures. In addition, I claim that several recent generalizations (of Rizzi, Levin and Rappaport, and Randall) are better formulated as deep syntactic properties than in terms of theta-roles.This syntactic approach to predicate-argument relations thus reinitiates a line of research implicit in Chomsky's Aspects but never developed. The first section argues that only this approach faithfully applies the syntactic revolution to lexical (headcomplement) semantics. Principles invoked include Chomsky's Full Interpretation and Rule for Agents and Talmy's Figure/Ground separation, along with a new Ground Specification and syntactic counterparts to two formal devices from Jackendoff's Conceptual Structures. The thematic role constellations for many verb classes (mostly but not all from English) are shown to follow from these principles. The conclusion speculates that the theta-roles assigned to a sentence are not its properties at a linguistic level, but rather indicate how that sentence is to modify cognitive representations.