In the tradition of political realism, this book provides an important reappraisal of the concept of human nature in contemporary realist international-political theory. With special reference to the anthropology of Sigmund Freud, a consequential yet terribly neglected and underestimated thinker in International Relations, Schuett demonstrates that analytical and normative theorizing of all international-political reality, its nature, tragedies, and potentialities, requires a sophisticated theory of human nature. Developing a Freudian philosophical anthropology for political realism, he argues for the careful resurrection of the concept of human nature in the wider study of international relations.