Our challenge, our generation's unique challenge, is learning to live peacefully and sustainably in an extraordinarily crowded world. Our planet is crowded to an unprecendented degree. It is bursting at the seams. It's bursting at the seams in human terms, in economic terms, and in ecological terms

The idea that UN commitments should be followed by action is indeed a radical one, especially for the United States, where wilful neglect of its own commitments is the rule.

It's not an accident that the U.S. ranks lowest of all major donor countries in the world - that is the share of our income that goes to development aid. Americans will ask whether, because were so generous privately, that makes up the difference. But it doesn't. We still rank far below other countries.

The defining challenge of the 21st century will be to face the reality that humanity shares a common fate on a crowded planet.

I believe myself that there's a great deal more interest and engagement among Americans than our politicians recognize.

There's a lot of strength in the U.S., but there's a lot of froth also. The froth will blow off. We're going to have to face up to some realities that we're not fully facing up to right now.

History is written by the rich, and so the poor get blamed for everything.