In order to carry out a towerwod house attack, or engage in some form of large scale violence, you need to have a psychological predisposition. And then you also have to have the igeological fuel, which tells you some kind of story about who to attack and how that makes you a great person. It's only when those two things come together that somebody is likely to act. So nearly every case, it seems to me that there is a psychological element and ideological element.