Why do people become terrorists?

How many times since the Holocaust, or the attrocities of the Khmer Rouge, or 9-11, have we wondered what was going through the minds of Adolf Hitler, Pol Pot or Osama Bin Laden? New Zealand philosopher and psychologist Professor Rom Harre has spent much of his professional life trying to understand why people do such things. He's analyzed the minds of al Qaeda terrorists and the language they use, and the CIA turned to Professor Harre to help explain why people become terrorists.