DescriptionThis dissertation asks and answers the question, "Why do threat identifications vary among presidents?" It considers four plausible explanations for differences in threat identification and concludes that a new approach, a rule-based (RBI) theory of threat identification, provides the most useful answer. The RBI approach posits that American identity is subjectively defined and varies among individuals. By analyzing the constitutive rules that a president uses to describe American identity, RBI theory explains the variation in the types of behavior that each president identifies as threatening. This dissertation concludes that how a president conceptualizes American identity will influence the types of threats he identifies. Its findings are based on a comparative case study of the presidents of the late nineteenth century. After examining the foreign policies of Grover Cleveland, Benjamin Harrison, and William McKinley, this study concludes that their different constructions of American identity account for disagreements over the British, German, and Spanish threats during the period studied. This dissertation and the RBI approach offer a novel and effective means for understanding late nineteenth century American foreign policy and put forward a template that can be applied to other eras, including the post-Cold War world.