War Is in the Error Term

The main theoretical task facing students of war is not to add to the already long list of arguments and conjectures but instead to take apart and reassemble these diverse arguments into a coherent theory t for guiding empirical research.1 At least since Thucydides, students of international relations have sought rational explanations for the advent of war. Rationalist explanations assume purposive ac-tion; states are said to make reasoned decisions about the use of force. Although rationalist explanations have proven persuasive, durable, and offer the basis for cu-mulative theorizing, they also imply substantial limits on what we can know about war. I show that the most general rationalist explanation for war also dictates that the onset of war is theoretically indeterminate. We cannot predict in individual cases whether states will go to war, because war is typically the consequence of variables that are unobservable ex ante, both to us as researchers and to the participants.2 Thinking probabilistically continues to offer the opportunity to assess international con ict empirically. However, the realization that uncertainty is necessary theoreti-cally to motivate war is much different from recognizing that the empirical world contains a stochastic element.Accepting uncertainty as a necessary condition of war implies that all other variables—however detailed the explanation—serve to elimi-nate gradations of irrelevant alternatives. We can progressively re ne our ability to distinguish states that may use force from those that are likely to remain at peace, but anticipating wars from a pool of states that appear willing to ght will remain prob-lematic. For example, we may achieve considerable success in anticipating crises, but our ability to predict which crises will become wars will probably prove little better than the naive predictions of random chance. The need for uncertainty to I am indebted to patient listeners, particularly my wife, Tara. Barbara Koremenos deserves special thanks for proposing the project’s form and outlet. I thankDavid H. Clark, John Conybeare, James Fearon