This book is the first systematic examination of the impact of reconciliation on restoring and maintaining peace following civil and international conflicts. Through eleven comparative case studies of civil war and eight of international conflict, it constructs a surprising explanation for when and why reconciliation restores social order.The civil war cases reveal that successful reconciliation is associated with a process of national forgiveness, not merely negotiated settlement. All successful cases followed a four-step pattern of public truth telling, justice short of revenge, redefinition of the identities of former belligerents, and a call for a new relationship. The book argues that success is not solely the result of rational choice decision making. It proposes a hypothesis, grounded in evolutionary psychology, that to restore social order we use emotional/cognitive techniques that have evolved to ensure human survival.On the international level, however, successful reconciliation was not a part of a forgiveness process. Reconciliation was successful in bringing about sustained peace when it was associated with a signaling process -- an exchange of costly, novel, voluntary, and irrevocable concessions in a negotiated bargain. This result is consistent with realist notions of the limits of international society and illustrates the context in which a rational choice model is appropriate. The book's approach, integrating emotion with reasoning and linking political science to scientific research in other disciplines, particularly biology and neuroscience, has broad implications for social science theory.