Don't let complexity stop you.

With world health, every life you save is a wonderful thing, so it's not this question of whether you solve it or you don't. The chance of completely solving the problems has long odds. But really, the thing is that you get to save the first child, the second child, the third child. You can just feel good about that.

When you revolutionize education, you're taking the very mechanism of how people be smarter and do new things, and you're priming the pump for so many incredible things.

The only role other than paying their taxes, whatever those are, the only role for philanthropy broadly - of which the rich should give disproportionately - the more, the better - and I think there is a positive trend in that direction - there are certain risk-taking things, like trying out a new type of charter school or funding a new kind of medicine.

The outpouring of support from millions of people in the immediate aftermath of the earthquake in Haiti has been impressive.

The world at large is less inequitable today than at any time in history. Number of people in abject poverty, as a percentage, is at all-time low.

Innovation is often the hidden thing, because we can't put numbers to it. And yet it's the thing that defines the way we live, the things we'd like to have for everyone whether it's health or education.