This article deals with the relation between the academic disciplines of International Relations and International Law in a historical perspective, so that an accurate comprehension of the current interdisciplinary debate can be brought to the fore. Thus, conventional conceptions about the main theories of International Relations - realism and liberalism - are discussed, and those theories are presented in a new light. Liberalism is conceived in the context of the convergence of international politics scholars and international lawyers until the development of a skeptical view in the field of International Law, which is responsible for the creation of realism in International Relations. The post-Cold War interdisciplinary debate is focused through three distinct theories: institutionalism, liberalism and constructivism. We argue that constructivism is more able to develop a deeper cooperation between international politics scholars and international lawyers. That is due to the connections between constructivism and critical theory, what allows joining constructivists and critical legal theorists in a Critical Agenda for International Relations and International Law in this beginning of the Twentieth-First Century.
International Relations; International Law; Liberalism; Realism; Constructivism; Critical Theory