Although it has often been said that violence begets violence, policy decisions rarely seem to reflect this ancient wisdom. Today's turbulent world of terrorism and counter-terrorism is certainly no exception, with violence being the tool of choice for all sides, and seemingly little regard for human life. This chapter discusses the psychological processes that lead terrorist groups and nations fighting against such groups to support violent solutions to their problems that entail the killing of multitudes of innocent people. By considering the psychological, social, and political forces that operate on both terrorist and counter-terrorist movements, we hope to avoid the infinite regress of blame that usually characterizes such discussions. We begin with a difficult but pivotal question: how can a human being justify the premeditated murder of innocent men, women, and children?

Such wanton killing violates the most basic definitions of morality shared by virtually all social institutions, religious and secular alike. In light of the extreme violence perpetrated by terrorists and the thousands killed as collateral damage in counter-terrorist campaigns, many feel that the answer must lie in the demonic nature of the perpetrators, who are often dismissed as archetypes of evil. Accepting this answer helps justify the violent course of action often taken in attempts to stop terrorism. If such evil exists, is it not our duty to eradicate the evil-doers to prevent the devastation of future attacks?