Today, more than ever before, science holds the key to our survival as a planet and our security and prosperity as a nation. It's time we once again put science at the top of our agenda and work to restore America's place as the world leader in science and technology.

No matter how long it takes, the United States will find and bring to justice the terrorists who are responsible for Kayla's captivity and death, ISIL is a hateful and abhorrent terrorist group whose actions stand in stark contrast to the spirit of people like Kayla.

The Cuban people must know that they have a friend and partner in the United States of America.

As president, I decided that a strong, confident America could advance our national security by engaging directly with the Iranian government. We've seen the results.

We are going through historic times, and my vision is a world, first of all, in which America continues to be that one indispensable nation. Because we're taking care of our own people, because our economy is strong and our middle class is growing, and people feel like hard work is rewarded, and we are continuing to expand opportunity and diversity and tolerance and respect.

If [black] nationalism could create a strong and effective insularity, deliver on its promise of self-respect, then the hurt it might cause well-meaning whites, or the inner turmoil it caused people like me, would be of little consequence.

I don't think I underestimated [Vladimir Putin], but I think that I underestimated the degree to which, in this new information age, it is possible for misinformation for cyber hacking and so forth to have an impact on our open societies, our open systems, to insinuate themselves into our democratic practices in ways that I think are accelerating.