This paper introduces some of the major themes of An Unwritten Future: Realism and Uncertainty in World Politics, and provides a short illustration of how the analytical apparatus elaborated there can offer fruitful insights into understanding enduring puzzles in international relations. An Unwritten Future explores, illuminates and interrogates Classical Realism, an approach to the study of world politics that is contrasted with Structural Realism and with the ‘hyper-rationalist’ perspective associated with the ‘Rationalist Explanations for War’ school of thought. It elucidates (...) the fundamental flaws of those two highly influential paradigms, and explains why Classical Realism, with its emphasis on what Structural Realism and Hyper-rationalism forbid—content, purpose, history, and irreducible uncertainty—provides a more promising and productive point of departure for students of international relations. (shrink)