This chapter explores the role of theological concepts in the genesis of modern international relations and focuses on the contrast between the Franciscan legacy and the Dominican heritage. It examines the historicist narrative of International Relations and traces it back to both Protestant and Catholic theology. The chapter explains how the modern notion of secular imperium as an autonomous. Most contemporary international relations scholarship lacks an account of both the historical influence and the contemporary relevance of rival theological approaches that shape thinking about modern international order. Much academic research and public political debate oscillates between Westphalian and post-Westphalian conceptions of international relations. The Westphalian account argues in favour of sovereign states, equal interstate relations, and non-interference in domestic affairs. The affirmation of subjective natural rights by Franciscan theologians such as Ockham paradoxically reinforces, rather than mitigates, the absolute power of the central sovereign.