In a recent article Emanuel Adler and Vincent Pouliot argued that attention to ‘practices’ could help IR scholars overcome ontological gaps and provide a new basis, on which the discipline could be established. Four such dichotomies are particularly salient: between the material and the meaningful, the rational and the practical, between agencies and structures, and between the forces of stability and of change. By failing to provide a theoretical basis for a synthesis, however, this project will fail. What a ‘practice’ is, and how ontological gaps should be understood, cannot be determined outside of the context of a theory. The article reviews theoretical attempts to deal with the dichotomies Adler and Pouliot identified and investigates the role of practices in the study of international relations.