One of the things that ultimately led me to leave mathematics and go into political science was thinking I could prevent nuclear war.

I told my father I had to try political science for a year. He thought I was throwing my life away.

It would be a huge mistake to abandon democracy promotion. Peaceful political change has been enormously successful in the past years in Eastern European countries as well as in countries like South Korea, South Africa, Chile and Indonesia. However, if possible, the use of force is something to avoid except in cases where genocide is threatened, like Bosnia or Libya or with regimes that threaten our security, like the Taliban and Saddam Hussein.

I think, in the longer view of things, there is a very powerful pull in the direction of participatory government.

I don't know of a single instance of these Arab freedom fighters holding up pictures of bin Laden. I know many instances of them displaying American flags in Benghazi or painting 'Facebook' on their foreheads in Cairo. The idea of freedom . . . is absolutely contradictory to what bin Laden stood for, which was . . . taking Muslims back to some medieval theocracy and encouraging people to die not for freedom but to go to paradise and to kill innocent people along the way. The contrast is really striking.

The only way you can be comfortable about Donald Trump's foreign policy, is to think he doesn't really mean anything he says.

NATO is still the most remarkable alliance in history. It stuck together through 40 years of Cold War, and it then joined together to fight in Afghanistan. In the 1980s, I would not have thought this was going to be possible.