Understanding how evangelicals shape United States foreign policy requires a solid grounding in the major theoretical lenses of international relations. These theories, most prominently realism and liberalism, offer systematic ways to interpret why and how states pursue power, build alliances, and promote values across the globe. Realism emphasizes national security interests and the distribution of power as central to state behaviour, while liberalism stresses the role of democratic ideals, international norms, and moral imperatives.