This piece of theory construction within the Government & Binding (GB) approach to syntax focuses on the base component and on the nature of phrase markers. Well-known structural facts about C-command, coordinate structures, adjuncts, and Islands are simply assumed, and a theoretical explanation for these structural facts is developed. The emphasis is on isolating theoretical primitives and deducing implications of these primitives through the articulation of a suitable theoretical architecture. Almost exclusively, considerations of coherence, simplicity, and organization are used to explain structural facts. Structure is the direct target of theory construction, rather than being derived from other considerations.