Realism has been the most influential theoretical approach in international relations since the discipline was born. Yet realism, for all its popularity, has always been criticised for its narrow world view of a system of states all seeking power, security and survival in a world of anarchy. Additionally, realism has struggled to provide explanations for some of the major events and evolutions in world politics. The timing of the outbreak of wars, the disappearance of superpowers and trends of regionalisation are all inadequately explained by realism, leaving the critic to ask, simply, why? Dylan Kissane answers this question by going to the core of realist theory and arguing that realism's problems stem from a critical yet flawed assumption about the nature of the international system. By assuming an anarchical system, realists diminish the complexity of international politics and blind themselves to the impact of substate actors. In this book, Kissane opens the door to re-founding international relations theory not on anarchy but on the assumption of a complex international system. Drawing on an interdisciplinary literature and offering a novel application of complexity theory to international politics, Beyond Anarchy is the beginning of a new and exciting stream of international relations theory for the twenty-first century.