In a lengthy new concluding chapter labeled "A Reply to Critics," Lon L. Fuller extends and clarifies his definition of the relation between law and morality put forward in the first (1964) edition of The Morality of Law. His original argument distinguishes between the morality of duty and the morality of aspiration, both of which bear on the design and operation of social institutions: the former by setting the necessary preconditions of any purposive social endeavor, the latter by suggesting the directions for such endeavor. In the revised edition, Fuller takes accurate aim at the school of legal philosophy called the New Analytical Jurists and continues his long-running debate with his major intellectual antagonist, H.L.A. Hart. Although the author calls the new chapter "A Reply to Critics," his expressed reason for undertaking it indicates that it is more than that: "As critical reviews of my book came in, I myself became increasingly aware of the extent to which the debate did indeed depend on 'starting points' - not on what the disputants said, but on what they considered it unnecessary to say, not on articulated principles but on tacit assumptions. What was needed, therefore, it seemed to me, was to bring these tacit assumptions to more adequate expression than either side has so far been able to do." There is no question that Mr. Fuller here gives the assumptions of his side adequate expression. "The volume must be regarded as an important contribution of general interest to the study of the nature and function of law...Trenchant comment abounds throughout the book, and there is an immense amount of the most valuable material here, as well as considerable food for the thought...his book deserves to reach a very wide audience." - Law Times."The book is a provocative one which is certain to excite much academic comment here and abroad." - Harvard Law Record."Although fully intelligible to the undergraduate, this book is likely to receive its warmest reception form advanced students of the philosophy of law, who will welcome the relief provided from the frequently sterile tone of much recent work in the field."--Choice