We know that if you have $20 million, it's better to buy a van Gough print than it is buy an executive jet, from the point of view of the environment. But when you start getting down, it's like the recycling question: What are things we can really afford to do, and how much pleasure do we get out of them? We haven't even started to have that discussion, and it's getting awfully late.

For example, I'm a great fan of pornography, but I don't see any reason not to restrict it so that people walking down the street who hate pornography don't have full color pictures outside of movie theaters. Let them be in a different district. I'm kidding about pornography, but you get the point.

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.

I see harm reduction as a way of engaging people as part of that path to recovery.

There are lots of excellent analysts out there. John Holdren at the Harvard Kennedy School, who was just president of the American Association for the Advancement of Science, has been talking about this stuff for years. There are lots of people out there who understand what’s going on. The problem is, they aren’t much picked up on Fox News.

I don't think scientists can dictate from above what we should do, because it's not a matter of scientific decision. If you want to have everybody living like a Beverly Hills millionaire, then 2 billion people might be too many. If we want to have a battery-chicken kind of world, with everybody having an absolute minimum diet, you might be able to support 10 billion.

If we were redesigning around people instead of around automobiles, which I think the market is more or less going to do, although too slowly, than I'd be a lot cheerier.