Joseph Raz (1939-2022) was a major philosopher of law of the last half century. But the reception of his legal philosophy has been shaped by relatively narrow debates about the nature of authority and the commitments of Hartian legal positivism.  A more comprehensive assessment of his achievements begins by considering the complex historical origins of his legal philosophy.  I consider three distinct historical strands relevant to understanding some of the central features and general framework of his philosophy of law: developments in moral, political, and legal philosophy regarding the importance of the concept of a reason for action, of the nature of political authority, and the systemic character of positive law, respectively, in the mid-twentieth century.  Raz’s legal philosophy can profitably be viewed as a novel convergence and synthesis of these many developments and influences, as an ambitious attempt to develop a systemic theory of positive law in terms of the concept of authority which is in turn explained from the perspective of practical reason.