The problem is not with the athletes, but with us. No matter how blatant the drug use may be, we don't stop watching the Tour de France. Maybe we should just turn off the television and get on our own bikes.

Take for example providing a guide dog for a blind person. That's a good thing to do, right? All right. It is a good thing to do. But you have to think what else you could do with the resources. It costs about $40,000 to train a guide dog and train the recipient so that the guide dog can be an effective help to a blind person. It costs somewhere between 20 and $50 to cure a blind person in a developing country if they have trachoma. So you do the sums, and you could provide one guide dog for one blind American or you could cure between 400 and 2,000 people of blindness.

If we all think only of our own interests, we are headed for collective disaster - just look at what we are doing to our planet's climate.

My fear is that that's what's going to happen with robotics and the military. Importantly, this discussion has to involve not just the scientists, but also the political scientists. It's got to be a multidisciplinary discussion. You can't have it be another repeat of what happened with the people working on the atomic bomb.

It is a mistake to assume that the law should always enforce morality.

I would not question the sincerity of vegetarians who take little interest in Animal Liberation because they give priority to other causes; but when nonvegetarians say that "human problems come first" I cannot help wondering what exactly it is that they are doing for human beings that compels them to continue to support the wasteful, ruthless exploitation of farm animals.

It is an indication of the extent to which people are now isolated from the animals they eat that children brought up on storybooks that lead them to think of a farm as a place where animals wander around freely in idyllic conditions might be able to live out their entire lives without ever being forced to revise this rosy image.