The article uncovers the intellectual link between Morgenthau’s theory of power politics and the German thinkers Max Weber and Carl Schmitt. Through this it sheds light on the forceful claims to objectivity contained in Morgenthau’s theory of power politics. The author reveals how, by combining Schmitt’s ideas of ‘the Political’ with Weber’s ideas on the objectivity of social science, Morgenthau finds an elegant way to overcome the value-determinacy of social science. This enables him to assert the objectivity of (international) political science. The same arguments allow Morgenthau also to formulate a moral defence of the state.