How and why does someone become a terrorist? Are there common causes? Is there a terrorist personality? To understand the psychology of those who engage in terrorism, John Horgan draws on interviews with terrorists and analyses current evidence to argue that only by asking the right questions about this complex problem, and by answering them only with evidence, can we truly begin to understand the nature of terrorism and how to respond effectively to it. Consequently this book presents a critical analysis of our existing knowledge and understanding of terrorist psychology, and in doing so, highlights the substantial shortcomings and limitations of the nature and direction of current research. Building on this, the author presents a model of involvement and engagement in terrorism by considering it as a process and exploring three distinct phases of the making of a terrorist: becoming involved, remaining involved (or 'being' a terrorist), and leaving terrorism behind. Despite the ongoing search for a terrorist personality, the most insightful and evidence-based research to date not only illustrates the lack of any identifiable psychopathology in terrorists, but demonstrates how frighteningly 'normal' and unremarkable in psychological terms are those who engage in terrorist activity. By producing a clearer picture of the complex processes that impinge upon the individual terrorist, a different type of terrorist psychology emerges, one which has controversial implications for efforts at countering terrorism in today's world. The book concludes with what this new psychology of terrorism means for understanding the terrorist and highlights what both researchers and the broader community can do to realistically engage the terrorist threat.