What is peace? This basic question often appears in contemporary orthodoxy to have been settled in favour of the 'liberal peace'. Yet, this has, in many post-conflict settings, proved to create a 'virtual peace'empty states and institutions which are ambivalent about everyday life. In this context peace is widely referred to but rarely defined. Though the concept of peace is often assumed to be normatively irreproachable, formative in the founding of the discipline, and central to the agendas of liberal states, it has rarely been directly approached as an area of study within IR. This essay endeavours to illustrate how developing accounts of peace helps chart the different theoretical and methodological contributions in IR, and the complex issues that then emerge. These include the pressing problem of how peace efforts become sustainable rather than merely inscribed in international and state-level diplomatic and military frameworks. This also raises issues related to an ontology of peace, culture, development, agency and structure, not just in terms of the representations of the world, and of peace, presented in the discipline, but in terms of the sovereignty of the discipline itself and its implications for everyday life. In an interdisciplinary and pluralist field of study - as IR has now become - concepts of peace and their sustainability are among those that are central. This raises the question of what the discipline is for, if not for peace? This paper explores such issues in the context of orthodox and critical IR theory, methods, and ontology, and offers some thoughts about the implications of placing peace at the centre of IR.