Theta Theory explores the lexicon as an interface in the strict sense, as facilitating the flow of information between cognition and the computational system of language. It argues for the traditional concept of a listed lexicon, where semantic roles are encoded as features of verbs, and against event decomposition. Part one of the book discusses the link between cognition and the lexicon. Mainstream theories of lexical semantics are critically reviewed. Furthermore, this part provides an extensive description of the relevant data in German, including agentivity, causation, psychological...