This work is the culmination of an 18-year collaboration between Ken Hale and Samuel Jay Keyser on the study of the syntax of lexical items. It examines the hypothesis that the behaviour of lexical items may be explained in terms of a very small number of very simple principles. In particular, a lexical item is assumed to project a syntactic configuration defined over just two relations, complement and specifier, where these configurations are constrained to preclude iteration and to permit only binary branching. The work examines this hypothesis by methodically looking at a variety of constructions in English and other languages.