A masterful exploration of the question of who becomes a terrorist and why, by the world's leading expert on the psychology of terrorism. Horgan explains how far our understanding has come since 9/11 and provides a blueprint for future studies. An essential primer about the complex mix of social conditions and psychology that lead individuals to turn to terrorist violence, and why and how they leave terrorism behind.–Jessica Stern, author of Terror in the Name of God: Why Religious Militants Kill