Writing has been an important exercise to clarify what I believe, what I see, what I care about, what my deepest values are. The process of converting a jumble of thoughts into coherent sentences makes you ask tougher questions.

As I've said many times, the nuclear deal was never intended to resolve all of our differences with Iran. But still, engaging directly with the Iranian government on a sustained basis for the first time in decades has created a unique opportunity, a window, to try to resolve important issues.

My first job as commander in chief is to keep the American people safe.

It is moments like these that force us to try harder, and dig deeper, and to discover gifts we never knew we had - to find the greatness that lies within each of us.

There is a word in South Africa - Ubuntu - that describes his greatest gift: his recognition that we are all bound together in ways that can be invisible to the eye; that there is a oneness to humanity; that we achieve ourselves by sharing ourselves with others, and caring for those around us.

There are folks who will equivocate. They'll say, 'You know, I'm not a scientist.' Well, I'm not either. But the best scientists in the world know that climate change is happening.

No discrimination, that's what we're about as a country.