This book occupies the same niche as Raymond Aron’s 1962 classic, Peace and War. While Aron wrote during the Cold War, Thierry de Montbrial writes about the post-Soviet international system, a system that is multipolar, ideologically heterogeneous, and thus highly unstable. In this book, he lays the foundation for a praxeology, or a “science of action,” to facilitate a better understanding of the dynamics of international problems and a more systematic approach to policy making. A major contribution to international relations theory and winner of the 2002 Georges Pompidou Prize, this book offers the necessary keys to decrypt the international system in the twenty-first century.