While the recent proliferation in philosophical discussions in International Relations indicates a welcome increase in the discipline’s conceptual sophistication, a central issue has gone relatively unremarked: the question of how to understand the relationship between scholarly observers and their observed objects. This classical philosophical problem has a number of implications for the conduct of inquiry in the discipline, and raises particular challenges for the status of knowledge-claims advanced by constructivists. I clarify these issues and challenges by distinguishing between ‘dualist’ and ‘monist’ ontological standpoints, in the hope of provoking a more focused philosophical discussion.