The United States often finds itself in a situation where if it goes in militarily then it is criticized for going in militarily, and if it doesn't go in militarily, then people say, why aren't you doing something militarily?

We want our children to live in an America...that isn't threatened by the destructive power of a warming planet.

The genius of our founders is that they designed a system of government that can be changed. And we should take heart, because we’ve changed this country before.

One of the things you learn as president is, as powerful as this office is, you have limited bandwidth. And the time goes by really quickly and you're constantly making choices, and there are pressures on you from all different directions - pressures on your attention, not just pressures from different constituencies. And so you have to be pretty focused about where can you have the biggest, quickest impact.

I'm inspired by my own children, how full they make my heart. They make me want to work to make the world a little bit better. And they make me want to be a better man.

I am a firm believer that you don't do anything significant by yourself. Again, maybe there are exceptions. There's the Picasso or the Mozart.

It is possible for leaders or regimes to be cruel, bigoted, twisted in their world views and still make rational calculations with respect to their limits and their self-preservation.