In this study the author seeks to develop Historical Realism as a new approach to International Relations. Drawing on recent theoretical developments in International Relations and Historical Sociology it is argued, first, that a distinction between constitutive and causal theory is necessary and, second, that this distinction makes comparisons at a high level of abstraction across time and space possible. The explanatory focus of Historical Realism is the political reproduction of states. States are seen as constantly facing a double security dilemma: it is being threatened, or potentially threatened, by two sets of rivals for revenue. At the level of abstraction of Historical Realism, states have two possible responses, short of collapse,...