How, given the absence of a universally shared set of values at the international level, may international rules possessing legitimacy be articulated? That is the question addressed by this article. Those who argue that international normativity enjoys relative independence from power relations or self-interest are confronted with the absence of a value consensus capable of undergirding a true sense of community at the international level and from which valid and legitimate rules may be derived. Claims that a community encompassing all of humanity is emerging have been made throughout history, and have been subjected, on the one hand, to charges of utopianism and idealism, and, on the other, to the criticism that such a community would simply mask the existence of fundamental disagreements regarding values and interests. (1) Many IR theorists interested in the problem of normativity have turned to social constructivism in an effort to place their project on more solid foundations. (2) The insights derived from these explorations are many and varied, and the uses to which they are put and the theoretical conclusions to which they contribute cover a wide spectrum. It may be useful to place the projects of these various authors into three categories in order better to identify some of the common themes uniting them and to understand the contributions that they make to international-relations theory. (3) According to one conception, which is inspired by democratic-peace theory, the fact of cooperative relations among certain states, particularly liberal democracies, leads to strong identification and a sense of mutual trust among those states. Based on these observations, attempts are made to identify the conditions for further community building at the international level. According to another conception, which draws on critical international theory and on a cosmopolitan approach to international relations, there is cause to be wary of arguments that the transmission of liberal-democratic values is a precondition to community building at the international level. Instead, a means for consensus building is sought that is not predicated on the universalizability of a set of values held by one group of states, (4) particularly if the group of states in question--namely, liberal democracies--wields disproportionate power in international society. The goal of critical cosmopolitanism is not to disseminate one worl dview but rather to build a consensus that leaves room for difference and diversity while being sufficiently substantial to provide the basis for the validity of norms. (5) A third conception holds that norms derive their validity not from commonly held values and a sense of community, but rather from intersubjective understandings that are constructed by agents in the course of interaction, and from which practices, rules, and institutions are constituted. While these intersubjective understandings normally constitute the background against which interactions take place, they can be critically examined by the agents who employ them and subjected to processes of argumentation through which they can be confirmed, modified, or reconstituted on the basis of reasons that participants in these processes accept. This article begins with a brief discussion of the theoretical approaches taken within each of these three conceptions. I then briefly explore social constructivism in international relations, and more particularly a social-constructivist conception of the regime as a site of international governance. I then discuss Jurgen Habermas's discourse ethics and seek to identify points of convergence between Habermas's project and international-relations theory. Finally, I argue that the regime, as described in social-constructivist terms, may operate as a forum for discourse and deliberation and as such may permit the articulation of international rules and norms grounded in consensus and therefore enjoying legitimacy. …