Now, we put out a lot of carbon dioxide every year, over 26 billion tons. For each American, it's about 20 tons. For people in poor countries, it's less than one ton. It's an average of about five tons for everyone on the planet. And, somehow, we have to make changes that will bring that down to zero.

In the philanthropy game, you're going for different outcomes: saving childhood lives, having kids grow up - because they don't have malnutrition or disease - that they achieve their full potential. We take for Warren [Buffett] things that, because he's very intelligent about the world but doesn't get to go out in Africa and see what we see, we've taken and say to him where we stand and it's basically a very positive report that his gift has made a phenomenal difference.

You wish that you could move more rapidly and you have setbacks. You know, the AIDS epidemic was a huge setback for Africa, and it's only through generosity that we've avoided that just completely crippling an entire generation there.

My wife thinks she's better than me at puzzles. I haven't given in on that one yet.

We're at the point now where the challenge isn't how to communicate effectively with e-mail; it's ensuring that you spend your time on the e-mail that matters most.

I believe innovation is the most powerful force for change in the world.

Humanity’s greatest advances are not in its discoveries – but in how those discoveries are applied to reduce inequity. Whether through democracy, strong public education, quality health care, or broad economic opportunity – reducing inequity is the highest human achievement.