This book develops ideas of Minimalist syntax to derive functional categories from the partially-ordered features expressed by functional elements, thereby dispensing with functional categories as primitives of the theory. It generalizes attempts to do this in the literature, while drawing significant empirical consequences from general constraints formulated to block overgeneration. The resulting theory of the construction of functional categories is applied to various problems in syntactic analysis and comparative and historical syntax, including variation across Germanic languages in patterns of verb-second and in the occurrence of expletive subjects in existential constructions, verb positions in Old and Middle English, problems regarding the placement of clitic pronouns in Romance languages and Modern Greek, and some previously unexamined structures of reduced clause coordination in colloquial English.