I certainly think it's important to speak up and say how unacceptable Donald Trump is. I'm always more than willing to do that.

After a regime is removed, however, it is dangerous to leave a security vacuum.

I think Obama sees everything through one lens. Doing nothing in the face of the slaughter in Syria is not only shameful, it is unrealistic. This approach leaves Syria as a broken country and a breeding ground for extremists for decades.

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

If the Arab world today looked like Tunisia, it would be a huge blow for the extreme ideologies. But Tunisia needs more support than it is getting, particularly from their close neighbors in Europe who have a great stake in North Africa.

You cant win if youre chasing the wrong problem.

Saddam Hussein had nerve gas and used it against his own people, he had used chemical weapons against the Iranians and he almost had a nuclear bomb in 1981 and in 1991. And he had been caught with anthrax in 1995 by the UN inspections after denying that he had it.