This volume offers new perspectives on the tension between the rich patterns of language variation that emerge from comparative studies and the quest for simple theoretical primitives. The chapters explore the debate between Cartography and Minimalism: on the one hand, the need for detailed and articulated descriptions of the clausal architecture, and on the other, the endeavor to reduce the theoretical apparatus to fundamental computational mechanisms. The first part of the book begins with a reflection on the goals of modern linguistic theory, and investigates the principles of human language, in an effort to subsume the regularities of particular grammars under a small set of morphosyntactic and semantic primitives. The second part examines the clausal structure - both the CP-layer and the IP-layer - from a comparative perspective, which directly relates to the fundamental questions of universality, linguistic variation, and learnability addressed in the first part of the book. With chapters written by world-leading linguists who analyze a wide range of old and new phenomena, the volume will be a valuable resource for researchers and students interested in theoretical linguistics and language development.