This article studies the contentious problem of reification in international relations (IR) on the example of the idea of international society. It shows how the idea became reified, that is, how the move was made from approaching international society as one of several competing frameworks for the study of international politics to considering it an objective fact, a self-evident reality of international politics, and an entity in the possession of agency. For this purpose, I trace key writings of the English school and survey their contribution to the idea’s development and gradual reification. I posit that reification has been the outcome of individual strategies and disciplinary practices pertaining to the knowledge production process, in particular the perceived need to establish and maintain a research program while continuing to provide viable explanations of world events. In discussing the consequences, I argue that reification adversely affects not only research outcomes but also the study process. A reified category, once it becomes a default language through which to think and talk about international politics, narrows down avenues for diverging interpretations of international politics. Furthermore, endowing international society with agency hides real agents behind specific actions in international politics.