This classic collection of essays, first published in 1979, has had an enduring influence on philosophical work on the nature of law and its relation to morality. Raz begins by presenting an analysis of the concept of authority and what is involved in law's claim to moral authority. He then develops a detailed explanation of the nature of law and legal systems, presenting a seminal argument for legal positivism. Within this framework Raz then examines the areas of legal thought that have been viewed as impregnated with moral values - namely the social functions of law, the ideal of the rule of law, and the adjudicative role of the courts. The final part of the book is given to understanding the proper moral attitude of a citizen towards the law. Raz examines whether the citizen is under a moral obligation to obey the law and whether there is a right to dissent. Two appendices, added for the revised edition, develop Raz's views on the nature of law, offering a further dialogue with the work of Hans Kelsen, and a reply to Robert Alexy's criticisms of legal positivism. This revised edition makes accessible one of the classic works of modern legal philosophy, and represents an ideal companion to Raz's new collection, Between Authority and Interpretation.