The discipline of International Relations (IR) for a long time of its history has developed in the form of Great Debates that involved competing paradigms and schools. More recently, it has been described as a cacophony of voices unable to communicate among themselves, but also incapable to provide keys to understand an ever more complex reality. This collection aims at evaluating the heuristic value of a selection of traditional paradigms (realism and liberalism), schools (constructivism), and subdisciplines (security studies and international political economy) so as to assess the challenges before IR theory today and the ability of the discipline to provide tools to make the changed world still intelligible.