One of the important qualities that I think is often overlooked is just energy. It's vitality, and sort of a life force that some people have and others don't. Probably that is connected to a love of whatever it is that they're doing. Another quality that I think is central is confidence. Again, some people are more blessed with that than others.

What the American Dream means to me is the fact that - what founded this country - when I think about those posters that were put up in Europe, which said, "Come to America and you'll have golden sidewalks. The land will be yours." There was something so inspirational about the fact that these immigrants from all over the world felt that here was a place of freedom, a place of opportunity.

I think the most important advice is, a person doesn't have to find out right away. It's not like their first attempt at finding a profession is the only one they're going to find. I might well have gone down other paths, and it still might have been okay. But if you find something that you love, and if it keeps deepening with each new experience, then just stay with it.

Where's the progress that we're going to see in Afghanistan? You have to keep public support both on the economy and the war or these things will really become troubling.

There is a sense of feeling larger than your own life when you're in some common mission together. You have to hope it's not going to take a war to bring that back to America again. I think another time when it seemed to be here was in the early 1960s.

As a historian, what I trust is my ability to take a mass of information and tell a story shaped around it.

Better to have your enemies inside your tent pissing out, then to have them outside your tent pissing in.