Were we incapable of empathy – of putting ourselves in the position of others and seeing that their suffering is like our own – then ethical reasoning would lead nowhere. If emotion without reason is blind, then reason without emotion is impotent.

If animals are no longer quite outside the moral sphere, they are still in a special section near the outer rim. Their interests are allowed to count only when they do not clash with human interests. If there is a clash - even a clash between a lifetime of suffering for a nonhuman animal and the gastronomic preference of a human being - the interests of the nonhuman are disregarded. The moral attitudes of the past are too deeply embedded in our thought and our practices to be upset by a mere change in our knowledge of ourselves and of other animals.

What one generation finds ridiculous, the next accepts; and the third shudders when it looks back on what the first did.

I don't think nationalism is alone holding the field; it's in contention with a lot of different things.

I don't see how anyone could really think that if you have a choice between saving the life of one person and saving the lives of a million people, to say - well, I've saved the one - can you really take that seriously? I can't.

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.

There is an obvious evolutionary explanation for the scarcity of altruistic saints: Without a strong predilection for their own interests, our ancestors would have been unlikely to survive, reproduce, and give their own offspring a chance of doing the same. Now conditions have changed and for most of us, surviving and reproducing isn't such a struggle but we still carry the genes of our ancestors and they influence - not determine, but influence - our behavior.