In this chapter, we explore some of the philosophical underpinnings of contemporary debates on the right to peace in international law. We believe that a discussion of a 'right to peace' has to take into account the history of how we understand and conceptualize rights as such, and how this understanding was always related to the question of peace. We explore ideas from early modern political thought and show how they are reflected in the positions of realism, internationalism, and cosmopolitanism on the role of international law in promoting peace. We demonstrate that these three positions represent three different conceptions of the connection between individual rights and the rights of states, resembling the views of Hobbes, Locke and Kant respectively. This leaves us with three different understandings of the right to peace, from a realist notion of a right to peace through the military power of states, to a liberal cosmopolitan notion of a right to peace through human rights-based constraints on sovereign statehood.