The opportunity will not remain open indefinitely.

Evil does exist in the world. A non-violent movement could not have halted Hitler's armies. Negotiations cannot convince al Qaeda's leaders to lay down their arms. To say that force may sometimes be necessary is not a call to cynicism - it is a recognition of history; the imperfections of man and the limits of reason.

I think when you're governing, it will become increasingly apparent that if you were to just eliminate trade deals with Mexico, for example, well, you've got a global supply chain. The parts that are allowing auto plants that were about to shut down to now employ double shifts is because they're bringing in some of those parts to assemble out of Mexico. And so it's not as simple as it might have seemed.

As I said in my State of the Union address ensuring the security of the United States and the safety of our people demands a smart, patient and disciplined approach to the world.

We've got to be able to distinguish between dangerous individuals who need to be incapacitated and incarcerated versus young people who are in an environment in which they are adapting, but if given different opportunities, a different vision of life, could be thriving the way we are. That's what strikes me. There but for the grace of God. And that, I think, is something that we all have to think about.

As you get older, your mind gets a little more set. And it needs the poking and prodding and breaking through of stereotypes that I think young people provide.

Any fool can have a child. That doesn't make you a father. It's the courage to raise a child that makes you a father.