This article examines the significance of the concept of agency for the project of critical theory as defined by Robert Cox. Even if numerous scholars recognize the importance of agency, very few have managed to set up an agenda that uses this notion in productive ways. I argue that this failure largely stems from the desire to present power as a structural phenomenon. If we see power as embedded in the very structure of society, it becomes difficult to see how social forces can escape the inherent tendencies imposed by structures. For this reason, the issue of social change has continued to elude critical theory making it difficult to open up space for an approach based on agency. Against structural conceptions of power, I present an agent-based conception of power which can serve to contextualize international relations in different terms. By presenting power in terms of practice, I argue, one can better overcome the reifying gaze of positivism.