This book is the first work to show this iconic legal philosopher's significance as a progressive political realist. In a lively account of Kelsen's life and political thinking, Robert Schuett introduces him as a political realist and brings his thought on human nature, the state and war into productive tension with today's Schmittians and conventional views of foreign policy realism. At a precarious moment in world history, where Western liberal principles are challenged by visions of illiberal democracy at home and abroad, this new reading of the Pure theory of law, state and international legal order is a timely defense of the ideals of an open society through a realistic style of politics.