Constraint theory defines for you what outcomes are possible and what outcomes are impossible. It also eliminates wishful thinking.

The United State has a net worth against which our debt is a joke ... we wrote in 2008 the United States is going to come out of this recession fast. The Europeans are going to fragment. The Chinese are going to be cremated. Why could we come out of it? Why has all economic theory been proven wrong? Because we're rich and we could afford it.

We cannot anticipate the moral circumstances under which we will live. And therefore [I refuse] to say that I will not live in a moral circumstance that requires violence.

The poets think about war more than the social scientists.

But every time new powers emerge they have to find their balance. New powers are emerging, old powers are declining. It's not that process that's dangerous, it's the emerging position that's dangerous.

The British bombed German cities [during World War II] to keep the workers awake at night. So instead of dropping one bomb, we sent a thousand planes and, yes, we took out the factory sometimes, but we also took out the city. It reached the point where we wanted more efficient ways to destroy a city. The result was nuclear weapons.

The importance of the question and the availability of an answer are two different things. I'm not willing to state that because the question is fundamental, therefore I possess the answer. And I'm certainly not willing to say that since I don't possess the answer, I'll pretend that I do.