Sub-Saharan Africa is also home to 400 million of the world's poorest people.

What really turns me on about technology is not just the ability to get more songs on MP3 players. The revolution - this revolution - is much bigger than that. I hope, I believe. What turns me on about the digital age, what excites me personally, is that you have closed the gap between dreaming and doing.

The fact is that ours is the first generation that can look disease and extreme poverty in the eye, look across the ocean to Africa, and say this, and mean it. We do not have to stand for this. A whole continent written off - we do not have to stand for this.

Sadly, I do my homework. I've a soft spot for the boring minutiae. I read the Charter of the United Nations before meeting with Kofi Annan. I read the Meltzer report, and then I'll read C. Fred Bergsten's defense of institutions like the World Bank and the I.M.F. It's embarrassing to admit.

The strangest thing has happened. I really missed my dog. That's never happened to me before. You know, on a long tour you do hear people saying they miss their pets. I never have. But last night I started really missing my dog. It's very odd, 'cause I don't have a dog.

If I don't understand it, it must be art.

The great music for so many artists - the Beatles, the Rolling Stones - was always at the moment when they were closest to pop. It would be easy for U2 to go off and have a concept album, but I want us to stay in the pop fray.