Stanford may be the best university in the world, but you can get all the way through here without knowing where your food came from, without being able to say where we came from, without being able to give a coherent description of why the climate is changing and why we should be concerned about it. So I started teaching a course in human evolution and the environment that's open to all Stanford students, no prerequisites.

Anyone who opposes methods to control the birth rate, is automatically voting in favour having the death rate go up.

To err is human, but to really foul things up you need a computer.

With taxes, if they aren't working right, we can change them with a stroke of the pen. It's basically a market-type mechanism. People make their own choices. You run the taxes, and you get the results.

I'm sort of optimistic about what we could do, but I'm very pessimistic about what we will do. I can't tell you that Al Gore's 10-year plan is impossible. I'm old enough to remember the Second World War - if we had a World War II-type mobilization, we might accomplish Gore's plan. In 1940 we were making tens of thousands of automobiles, and in 1941 we were making tens of thousands of airplanes. We mobilized as a nation. If we get that kind of mobilization as a nation or globally, then we could solve a lot of these problems.

So, regarding the time frame, I'm only too willing to admit that my crystal ball, like everybody else's, is cracked. If I could predict precisely, I would have started predicting the stock market and would now be living with a bunch of young women on Bora Bora, having bought it.

There are a lot of signs. One of the things that makes me most nervous is the disappearance of the frogs. They're going downhill all over the planet. Frogs are susceptible to all kinds of problems, because they require water to breed and their skin is very porous. Their condition is nerve racking.