What is Empathy? How Can We Get More Of It?

With today being 9/11, I always think of empathy. I wonder where it went that morning and how people could have done something like that to other people. As a result, I wrote my English Lit dissertation on this subject because I needed to make some kind of sense of what happened that morning here in NY and Va and Pa. I wrote a 47 page dissertation and I still don't have the answer. What is it? Where did it go that morning? How do we get more? Pax - C