Now, al Qaeda's on the run. Afghanistan is no longer a base of operations. The Afghan government is a friendly government that is trying to bring democracy to its people.

This is not 1968 and the invasion of Czechoslovakia, where Russia can threaten its neighbors, occupy a capital, overthrow a government, and get away with it. Things have changed.

We've organized human potential and have been better at using human potential better than any country on the face of the Earth. That's because we've recognized that our national creed, our national identity, is that it doesn't matter where you're from, it matters where you're going. You can come from hard circumstances and do great things. We've got to make that true for a whole variety of people who no longer feel that.

Tocqueville talked about "ceaseless agitation," citizens constantly use their institutions, constantly challenging them, constantly insisting upon their rights. It's also individuals taking responsibility for other individuals, recognition that no democracy works if they're weaklings.

We need a common enemy to unite us.

I'm actually genuinely optimistic about the United States and what's possible in the United States. And when you're out here, you see Americans across racial and economic and socioeconomic lines working together. And you maybe get a little bit less cynical than when you sit in the seat of kind of the epicenter of it all.

Fortunately, I started very young, so I read music very well. And my favorite composers to play are Brahms and Mozart.