The contemporary interest in studying religion in international relations (IR) is particularly important, because it can offer insight into the exact characteristics that led to its exclusion from IR in the first place. These characteristics are its appeal to what most people instinctively would describe as the ‘irrational’, more specifically to emotions, and their ability to infuse a high degree of passion and devotion into a political cause. This chapter deals with the relationships between religion, emotions and conflict escalation. I show that collective emotions are interlinked with cognitive processes and representational practices in which religious ethics, or conceptions of right and wrong, good and evil, play a role. Collective emotions – sometimes also referred to as higher-order, cognitive or moral emotions – are of particular value for understanding justificatory practices embraced by violent religious movements and the dynamics of conflict escalation.