I feel somewhat obligated to do some sort of a 9/11-themed post here. I don't have anything in particular to add about the political or moral lessons of that day -- others have done this far better than I could.
I consider myself fortunate that I didn't know anyone who died that day. Strangely, one of the memories that lingers with me is the time my grandfather took me to lunch at Windows on the World, the restaurant at the top of One World Trade Center, probably in 1979 or 1980, when I was around ten years old. I can still remember sipping cocoa and watching the city far, far below. We were just two of the probably hundreds of thousands of people who ate there during the restaurant's 25-year existence, but it was a special treat for me at the time. It is unsettling to me that I am the only thing remaining from that event.