  The keystone of Morgenthau’s realist theory is the concept of power or “of interest defined in terms of power,” which informs his second principle: the assumption that political leaders “think and act in terms of interest defined as power” (5). This concept defines the autonomy of politics, and allows for the analysis of foreign policy regardless of the different motives, preferences, and intellectual and moral qualities of individual politicians. Furthermore, it is the foundation of a rational picture of politics.