The role of sovereign authority in Hobbes' political philosophy is to establish peace and stability by serving as a definitive and unambiguous source of law. Although these broad outlines of Hobbes' account of political authority are uncontentious, matters quickly become more complicated once one seeks its normative basis. This much is evident from recent debates on the normative status of the laws of nature and the related issue as to whether Hobbes is better categorised as an incipient legal positivist or (...) as a heterodox natural law thinker. In this paper I argue that although the positivist and natural law commitments in Hobbes' theory of political authority can be partially reconciled, such a reconciliation points to the need for more substantive theories of practical reason and truth than are to be found in Hobbes' official statements on these topics. Section II examines the positivist and natural law dimensions in Hobbes' thought and suggests that the role of sovereign authority in providing the definitive interpretation of the laws of nature allows a partial reconciliation to be effected. In section III, I consider the tension between this reconciliation and Hobbes' instrumentalism about practical reason and equivocal separation of authority and truth. (shrink)