Defining Rationality in Security Studies: Expected Utility, Theory-Driven Reasoning, and the Vietnam War

In How States Think, John Mearsheimer and Sebastian Rosato argue that expected-utility maximization is too subjective to serve as the basis for making rational decisions in the realm of national security. They claim that rationality in security studies should instead be defined by whether leaders conduct deliberative, theory-driven reasoning. This essay explains why Mearsheimer and Rosato's critique of expected-utility theory is unpersuasive, and how their conception of theory-driven reasoning ignores key aspects of decision-making that national security officials can feasibly address. Lyndon Johnson's decision to take the United States to war in Vietnam provides a vivid example of how leaders can meet Mearsheimer and Rosato's criteria for rationality despite clear shortfalls of analytic reasoning.