I believe that the free enterprise system is the greatest engine of prosperity the world's ever known.

No challenge poses a greater threat to future generations than climate change.

If you don't have good people, and you don't have a good process and you don't have, at some level, the basic reverence for [presidential] office, and an understanding of the incredible responsibilities and obligations, then, I think you can get into trouble.

We are defined not by our borders but by our bonds.

Over more than a decade, Iran had moved ahead with its nuclear program. And before the deal, it had installed nearly 20,000 centrifuges that could enrich uranium for a nuclear bomb.

We're not going to deputize a whole bunch of American citizens to start grabbing people or turning them in, in part because the ordinary American citizen may not know whether or not this person is illegal or not. But, you know, the notion that we're going to criminalize priests, for example, or doctors who are providing services to individuals, and throw them in jail for doing what their calling asks them to do, which is to provide help and service to people in need, I think that is a mistake. I think that's out of America's character.

Isil poses a threat to the people of Iraq and Syria, and the broader Middle East - including American citizens, personnel and facilities. If left unchecked, these terrorists could pose a growing threat beyond that region, including to the United States.