Each of us spends money on things that we do not really need. You could take the money you're spending on those unnecessary things and give it to this organization the Against Malaria Foundation which would take the money you had given and use it to buy nets to protect children. And we know reliably that if we provide nets, they're used, and they reduce the number of children dying from malaria. Fortunately more and more people are understanding this idea, and the result is a growing movement effective altruism.

If we can put a man on the moon and sequence the human genome, we should be able to devise something close to a universal digital public library.

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.

Suppose I grant that pigs and dogs are self-aware to some degree, and do have thoughts about things in the future. That would provide some reason for thinking it intrinsically wrong to kill them - not absolutely wrong, but perhaps quite a serious wrong. Still, there are other animals - chickens maybe, or fish - who can feel pain but don't have any self-awareness or capacity for thinking about the future. For those animals, you haven't given me any reason why painless killing would be wrong, if other animals take their place and lead an equally good life.

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.

We are not especially 'interested in' animals. Neither of us had ever been inordinately fond of dogs, cats, or horses in the way that many people are. We didn't 'love' animals.

One thing is certain: you will find plenty of worthwhile things to do. You will not be bored, or lack fulfillment in your life. Most important of all, you will know that you have not lived and died for nothing, because you will have become part of the great tradition of those who have responded to the amount of pain and suffering in the universe by trying to make the world a better place.