We certainly would resolve the problems of the charities that are working in areas where they can do the most good. So if you consider that the U.S. foreign aid budget is 30 billion, yes, we could make a major contribution to reducing global poverty, start to deal much better with some of the other big environmental problems that the world faces. So I think we could solve a lot of problems.

If you go back in time you'll find tribes that were essentially only concerned with their own tribal members. If you were a member of another tribe, you could be killed with impunity.

We don't usually think of what we eat as a matter of ethics. Stealing, lying, hurting people - these acts are obviously relevant to our moral character. In ancient Greece and Rome, ethical choices about food were considered at least as significant as ethical choices about sex.

If possessing a higher degree of intelligence does not entitle one human to use another for his or her own ends, how can it entitle humans to exploit non-humans?

I don't think there's anything in the compromise that means that there's a clash of ethics.

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.

I know of a number of people who are successfully earning to give. That isn't for everyone but for those with the ability to earn a lot of money and the character to resist the temptation to spend it on themselves, it can be a great way to do good.