Here is a very brief summary of a position that I have defended on many occasions, most fully in my book Animal Liberation (see Singer, 1990): our present treatment of animals is based on speciesism; that is, a bias or prejudice towards members of our own species, and against members of other species. Speciesism is an ethically indefensible form of discrimination against beings on the basis of their membership of a species other than our own. All sentient beings have interests, and we should give equal consideration to their interests, irrespective of whether they are members of our species or of another species.
My aim in this chapter is to defend this position and explain why I hold to it, despite criticisms both from those who seek to defend a speciesist ethic and from those who think that the kind of ethic I hold does not go far enough. It is the latter criticism, in particular, that I address here. While animal liberationists and deep ecologists agree that ethics must be extended beyond the human species, they differ in how far that extension can intelligibly go. If a tree is not sentient, then it makes no difference to the tree whether we chop it down or not. It may, of course, make a great difference to human beings, present or future, and to non-human animals who live in the tree, or in the forest of which it is a part. Animal liberationists would judge the wrongness of cutting down the tree in terms of the impact of the act on other sentient beings, whereas deep ecologists would see it as a wrong done to the tree, or perhaps to the forest or the larger ecosystem. I have difficulty in seeing how one can ground an ethic on wrongs done to beings who are unable to experience in any way the wrong done to them, or any consequences of those wrongs. So hereafter I will be concerned with a position based on consideration of the interests of individual sentient beings.
From the perspective of deep ecologists, the non-speciesist ethic I am advocating seems to stick too closely to traditional ethical viewpoints. It is, for example, compatible with classical utilitarianism, which judges acts as right or wrong by asking whether they will lead to a greater surplus of pleasure over pain than any other act open to the agent. As the great classical utilitarian