To be honest, I was somewhat disappointed... It's had effects around the margins, of course, but they have mostly been minor. When I wrote it, I really thought the book would change the world. I know it sounds a little grand now, but at the time the sixties still existed for us. It looked as if real changes were possible, and I let myself believe that this would be one of them. All you have to do is walk around the corner to McDonald's to see how successful I have been.

I am a utilitarian. I am also a vegetarian. I am a vegetarian because I am a utilitarian.

At one level, this movement on behalf of oppressed farm animals is emotional...Yet the movement is also the product of a deep intellectual ferment pioneered by the Princeton scholar Peter Singer...This idea popularized by Professor Singer - that we have ethical obligations that transcend our species - is one whose time appears to have come...What we're seeing now is an interesting moral moment: a grass-roots effort by members of one species to promote the welfare of others...animal rights are now firmly on the mainstream ethical agenda.

I regard Peter as one of the great moralists, because I suspect that more than anyone he has helped to change the attitudes of very many people to the sufferings of animals. Peter is a utilitarian in normative ethics, and a humane attitude to animals is a natural corollary of utilitarianism. Utilitarian concern for animals goes back to Bentham, who, presumably alluding to the Kantians, said that the question was not whether animals can reason, but whether they can suffer.

The kind of equality utilitarianism supports is given by Bentham's formula...: 'everybody to count for one, and nobody for more than one'...Utilitarianism seeks to maximize happiness, and in deciding how to calculate whether happiness is being maximized, no one's pleasures or pains should count for less because they are peasants rather than aristocrats, slaves rather than slave-owners, Africans rather than Europeans, poor rather than rich, illiterates rather than doctors of philosophy, children rather than adults, females rather than males, or even, as we have seen, non-human animals rather than human beings.

The fact that no one has come up with a really convincing reason for giving greater moral weight to members of our own species, simply because they are members of our species, strongly suggests that there is no such reason. Like racism and sexism, speciesism is wrong.

Animals no doubt have different interests from humans, and may experience different pleasures and pains, but the principle of equal consideration for similar interests still holds, and pleasures and pains of similar intensity and duration should be given equal weight, whether they are experienced by humans or by animals.

September 11, 2001, was just another day for most of the world's desperately poor people, so presumably close to 30,000 children under five died from these causes on that day-about ten times the number of victims of the terrorist attacks. The publication of these figures did not lead to an avalanche of money for UNICEF or other aid agencies helping to reduce infant mortality. In the year 2000 Americans made private donations for foreign aid of all kinds totaling about $4 per person in extreme poverty, or roughly $20 per family. New Yorkers who were living in lower Manhattan on September 11, 2001, whether wealthy or not, were able to receive an average of $5,300 per family. The distance between these amounts encapsulates the way in which, for many people, the circle of concern for others stops at the boundaries of their own country-if it extends even that far.

One common strategy on which we should all be able to agree is to take steps to reduce the risk of human extinction when those steps are also highly effective in benefiting existing sentient beings. For example, eliminating or decreasing the consumption of animal products will benefit animals, reduce greenhouse gas emissions, and lessen the chances of a pandemic resulting from a virus evolving among the animals crowded into today's factory farms, which are an ideal breeding ground for viruses. That therefore looks like a high-priority strategy.

Remember Bostrom's definition of existential risk, which refers to the annihilation not of human beings, but of "Earth-originating intelligent life." The replacement of our species by some other form of conscious intelligent life is not in itself, impartially considered, catastrophic. Even if the intelligent machines kill all existing humans, that would be...a very small part of the loss of value that Parfit and Bostrom believe would be brought about by the extinction of Earth-originating intelligent life. The risk posed by the development of AI, therefore, is not so much whether it is friendly to us, but whether it is friendly to the idea of promoting wellbeing in general, for all sentient beings it encounters, itself included.