Book excerpt: One of the major purposes of my study is to extract the systematic features of the terrorist incidents of 9/11 and 5/16, and try to get the lessons. Knowing what happened on a given occasion is not sufficient by itself. If we make no effort to extract the systematic features of the subject; the lessons of history will be lost, and we will learn nothing about what aspects of our subject are likely to persist or to be relevant to future events or studies.