This book is an in-depth analysis of the classic works of leading theorists in the realist school of international relations. It criticizes the works of Carr, Morgenthau and Waltz, and their contributions to the continuous building and rebuilding of realism. It highlights their problematic assumptions, internal inconsistencies and failures to address important aspects of international relations. It also criticizes later realist attempts to fix serious problems of Waltz’s theory in order to save the realist paradigm in international relations. Criticisms are based on a constructivist point of view The first argument is that at least some constructivist theories are compatible with realism in spite of a general lack of recognition of this compatibility in the international relations literature. The second argument is that constructivism is embedded in realism. The realist paradigm was founded and developed in part on ideational concepts later claimed by social constructivists. The third argument is that realism also has something to offer constructivism, especially the potential of solving serious constructivist puzzles, notably the insufficiency of the logic of appropriateness.