The relative weight and interaction of structural and cultural factors remains a central preoccupation of international relations theory today. This is particularly evident in the recent surge of interest in contemporary Islamic conceptions of conflict and cooperation. This paper explores the state of the field through an investigation of what may be described as the "reformist" school of Islamic thought on international affairs, represented by modern scholars such as Muhammad Shaltut, Muhammad Abu Zahra, `Abd al-Khaliq al-Nawawi, and Wahba al-Zuhayli. First, the paper will clarify the contrasts between this reformist school and what is often called the "classical doctrine" – originating with the jurists of the `Abbasid period – on critical questions such as the legitimacy of offensive (as opposed to defensive) war, and the extent of permissible cooperation with non-Muslim polities. Second, the paper will explore the conceptual underpinnings of such contrasts, including the reformist emphasis on historicism (the notion that much of the classical doctrine reflected transient historical exigencies that may be abrogated); its reliance on the well-being of the community/polity as the ultimate standard for conduct in international affairs; its consequent privileging of state sovereignty; and its overall conclusion that peace is the basis of a true Islamic understanding of international politics. Finally, the paper will assess the strengths and weaknesses of the reformist approach through a comparison with an alternative approach developed in the medieval period – one represented by figures such as the author of the early `Abbasid treatise Mukhtasar Siyasat al-Hurub, and Ibn Khaldun. This comparison will suggest that the modern reformist school has yet to refine its ideas on certain core tensions between religion and realpolitik in the formulation and conduct of foreign policy, particularly on the question of imperialism. My sources are the primary texts on international politics of the representative figures of the three approaches mentioned here: the reformist, the classical, and the "Ibn Khaldunian."