The book examines five principal areas or directions of interdisciplinary study: economics, history, psychology, the epistemology of law and the empirical study of law. These approaches are seen to interpenetrate and to compose a coherent body of legal theory--a unified framework for understanding such seemingly disparate phenomena as the economics of free speech, the intellectual history of economic analysis of law, the relation between income and liberty, the law of possession, the psychology of legal decision-making, the role of emotion in law, and the use of citation analysis to evaluate judges and law professors. The book carries on Posner's project of analyzing the law as an institution of social governance.