There is a great deal of primary source evidence available on terrorists’ motivations, aspirations, and justifications. They appear in interviews with imprisoned terrorists and in the publications and Web sites of terrorist groups. I also spoke to any terrorist I could. In the days before September 11, 2001, this was a lot easier than it has been since.

On one occasion a few years ago, some colleagues and I convened a group of what we politely termed “activists,” representatives from a number of ethnonationalist terrorist groups, for a secret conference in a private location. We met for several days, during which we conducted ourselves much like an academic conference. I gave a paper on the factors driving terrorists’ decisions to escalate, and a senior member of a well-known terrorist group served as commentator on my paper. He politely pointed out where he thought I was right and where he disagreed, where my generalizations applied to his movement and where they did not. We all socialized together for several days. It was soon difficult to tell to which camp an individual belonged.

[…]

With colleagues, I helped to organize a second similar gathering, this time with representation from religious terrorist groups. We were scheduled to meet from September 11 to 14, 2001. Six weeks before the planned meeting, worried that one of the groups might make the meeting public and when one of the insurgent groups insisted that there could be no Jews among the academics, we decided to cancel. I have often imagined what it would have been like to have been in that company on that day.

–Louise Richardson, What Terrorists Want