Since constitutional arrangements are what make politics work, they are a central concern of political theory. This book, now completely updated, is the first comprehensive exploration of the political theory of constitutions. Jan-Erik Lane begins by examining the origins and history of constitutionalism and answers key questions such as: What is a constitution? Why are there constitutions? From where does constitutionalism originate? How is the constitutional state related to democracy and justice? Constitutions play a major role in domestic and international politics in the early 21st century and an updated version of this classic textbook will introduce students to a number of different areas -- theoretical, empirical, and moral -- which will aid their understanding of this important topic.