Dueling realisms

International relations scholars largely focus on realism's common features: what has been overlooked is that realists diverge regarding a series of assumptions about state behavior. This article divides realism into two competing branches by exposing these latent divisions. Realists are shown to diverge regarding (1) whether states are conditioned by the possibility--or alternatively the probability--of conflict, (2) how states weigh short-term versus long-term objectives, and (3) how states trade off military security versus economic capacity. To demonstrate the significance of these divergent assumptions, competing hypotheses are outlined regarding German and Japanese foreign policy, nuclear proliferation in Ukraine, and regional economic cooperation among developing countries. Dividing realism on this basis opens up avenues for cumulative intra-realist debate that have heretofore been closed. Furthermore, a clear understanding of realism's two branches helps to explain why past interchanges with nonrealist theories have generally been disappointing and should make it possible to initiate more productive future dialogue.