Chapter 2 develops a theoretical framework for explaining how ideational and material forces shape states’ threat perceptions as well as the conditions for their interplay. This chapter develops the conception of security as both physical and ontological, in which the interaction of ideational and material forces can be analysed. The chapter shows that in some cases, ideational sources of threat are perceived as predominant, and, in other cases, material factors shape threat perception. To explain this variation, the chapter outlines the conditions of the interplay between ideational and material forces, based on the fluidity of the regime identity – assessed through mutability of the regime identity narrative – and the clarity of the relative power distribution – assessed through the multiplicity of available policy options to ensure physical security. The chapter also includes a research design section that discusses methods and case selection criteria. The book then explores the plausibility of this framework empirically by examining a number of cases that have been at the heart of historical and theoretical work on the international relations of the Middle East.