In setting out to write this paper, my intention was to fill a gap in my book Animal Liberation. There I argued that the interests of animals ought to be considered equally with our own interests and that from this equality it follows that we ought to become vegetarian. The argument for vegetarianism is not based on any claim about the wrongness of killing animals—although some careless reviewers read this claim into my book, no doubt because they assumed that any moral argument for vegetarianism must be based on the wrongness of killing. Instead the argument for vegetarianism is based on the suffering that is, and as far as I can see always will be, associated with the rearing and slaughtering of animals on a large scale to feed urban populations. I explicitly avoided taking a position on the wrongness of killing animals, for I wanted the book to reach non-philosophers, and the issue of killing cannot be dealt with briefly and simply.
(Peter Singer, "Killing Humans and Killing Animals," Inquiry 22 [summer 1979]: 145-56, at 145 [italics in original; endnote omitted])