War to me is very much like sex. You can develop a theory that says sex is primarily for the exchange of genetic material, or that it's a celebration of life, or you can make up 50,000 theories about why human beings have sex, all of which are in some sense true, all of which by themselves miss the point. Because the answer is extraordinarily complex. It may be for fun, it may be for reproduction, for financial reasons, any number of things.

War and sex are what I call the two abysmal - by that I mean deep - parts of the human condition.

When you're young and going to war, it's a genuinely exciting moment. You are going to risk yourself. On the battlefield, you are suddenly free. You realize: I'm here, I'm in it. Exaltation. Suddenly you're hit by another extraordinary feeling: my God, I can be killed. And: will I embarrass myself? It's like you're in a kaleidoscope and all of these extraordinary feelings are zipping by.

In a way, we can have a much easier discussion about the future of technology than we can about why a young man kills another man in a war.

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

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.

I'm not a journalist. So I didn't down and let Assad charm me. I didn't walk away and say "my god he's got an Apple computer and he really likes Beyonce so he must be a liberal."