The pioneering work of Judge Richard Posner has brought to light the broad relevance of economics to virtually all areas of law. During the last three decades of the 20th century, Judge Posner provided seminal contributions to the development of an overarching economic theory of law, with applications including traditional legal subjects, such as torts and contracts, as well as non-standard topics, such as his study of primitive law and ancient customs. This selection of Judge Posner's essays reveals the importance of economic efficiency as a driving force in the formation of legal rules and, along with a rigorous introduction by Professor Parisi, demonstrates Judge Posner's unparalleled influence on the role of economics in private law.