This book [In Defense of Animals] provides a platform for the new animal liberation movement. A diverse group of people share this platform: university philosophers, a zoologist, a lawyer, militant activists who are ready to break the law to further their cause, and respected political lobbyists who are entirely at home in parliamentary offices. Their common ground is that they are all, in their very different ways, taking part in the struggle for animal liberation. This struggle is a new phenomenon. It marks an expansion of our moral horizons beyond our own species and is thus a significant stage in the development of human ethics. The aim of this introduction is to show why the movement is so significant, first by contrasting it with earlier movements against cruelty for animals, and then by setting out the distinctive ethical stance which lies behind the new movement.

Although there were one or two nineteenth-century thinkers who asserted that animals have rights, the serious political movement for animal liberation is very young, a product of the 1970s. Its aims are quite distinct from the efforts of the more traditional organizations, like the Royal Society for the Prevention of Cruelty to Animals, to stop people from treating animals cruelly. Even these traditional concerns, however, are relatively recent when seen in the context of 3,000 years of Western civilization, as a brief glance at the historical background to the contemporary animal liberation movement will show.

Concern for animal suffering can be found in Hindu thought, and the Buddhist idea of compassion is a universal one, extending to animals as well as humans, but our Western traditions are very different. Our intellectual roots lie in Ancient Greece and in the Judeo-Christian tradition. Neither is kind to those not of our species.

In the conflict between rival schools of thought in Ancient Greece, it was the school of Aristotle that eventually became dominant. Aristotle held the view that nature is a hierarchy in which those with less reasoning ability exist for the sake of those with more reasoning ability. Thus plants, he said, exist for the sake of animals, and animals for the sake of man, to provide him with food and clothing. Indeed, Aristotle took his logic a step further- the barbarian tribes, which he considered obviously less rational than the Greeks, existed in order to serve as slaves to the more rational Greeks. He did not quite have the nerve to add that philosophers, being supremely rational, should be served by everyone else!

Nowadays we have rejected Aristotle's idea that less rational human beings exist in order to serve more rational ones, but to some extent we still retain that attitude towards non-human animals. The social reformer Henry Salt tells a story in his autobiography, Seventy Years Among Savages (an account of a life lived entirely in England), of how, when he was a master at Eton, he first broached the topic of vegetarianism with a colleague, a distinguished science teacher. With some trepidation he awaited the verdict of the scientific mind on his new beliefs. It was: 'But don't you think that animals were sent to us for food?' That response is not far from what Aristotle might have said. It is even closer to the other great intellectual tradition of the West — a tradition in which the following words from Genesis stand as a foundation for everything else:

And God said, Let us make man in our image, after our likeness: and let them have domination over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.

So God created man in his own image ....

And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it; and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.

Here is a myth to make human beings feel their supremacy and their power. Man alone is made in the image of God. Man alone is given dominion over all the animals and told to subdue the earth. One may debate, as environmentally concerned Jews and Christians have done, whether this grant of dominion entitles human beings to rule as petty despots, doing as they please with the unfortunate subjects placed under their jurisdiction, or whether it was not rather a kind of stewardship, in which humans are responsible to their Lord for the proper care and use of what has been placed in their custody. One can point to one or two Christian figures, like John Chrysostom and Francis of Assisi, who have shown compassion and concern for non-human Creation. (Though even the stories about Francis are conflicting. There is one episode in which a disciple is said to have cut a trotter off a living pig in order to give it to a sick companion. According to the narrator, Francis rebuked the disciple - but for damaging the property of the pig owner, not for cruelty to the pig!) So far as the history of Western attitudes to animals is concerned, however, the 'dominion' versus 'stewardship' debate and that over the true nature of the teachings of Francis are both beside the point. It is beyond dispute that mainstream Christianity, for its first 1,800 years, put non-human animals outside its sphere of concern. On this issue the key figures in early Christianity were unequivocal. Paul scornfully rejected the thought that God might care about the welfare of oxen, and the incident of the Gadarene swine, in which Jesus is described as sending devils into a herd of pigs and making them drown themselves in the sea, is explained by Augustine as having been intended to teach us that we have no duties towards animals. This interpretation was accepted by Thomas Aquinas, who stated that the only possible objection to cruelty to animals was that it might lead to cruelty to humans - according to Aquinas, there was nothing wrong in itself with making animals suffer. This became the official view of the Roman Catholic Church to such good — or bad — effect that as late as the middle of the nineteenth century Pope Pius IX refused permission for the founding of a Society for the Prevention of Cruelty to Animals in Rome, on the grounds that to grant permission would imply that human beings have duties to the lower creatures.

Even in England, which has a reputation for being dotty about animals, the first efforts to obtain legal protection for members of other species were made only 180 years ago. They were greeted with derision. The Times was so dismissive of the idea that the suffering of animals ought to be prevented that it attacked proposed legislation that would stop the 'sport' of bull-baiting. Said that august newspaper: 'Whatever meddles with the private personal disposition of man's time or property is tyranny.' Animals, clearly, were just property.

That was in 1800, and that Bill was defeated. It took another twenty years to get the first anti-cruelty law on to the British statute books. That any consideration at all should be given to the interests of animals was a significant step beyond the idea that the boundary of our species is also the boundary of morality. Yet the step was a restricted one because it did not challenge our right to make whatever use we chose of other species. Only cruelty - causing pain when there was no reason for doing so but sheer sadism or callous indifference - was prohibited. The farmer who deprives his pigs of room to move does not offend against this concept of cruelty, for he is considered to be doing only what he thinks necessary to produce bacon. Similarly, the scientist who poisons a hundred rats in order to determine the lethal dose of some new flavouring agent for toothpaste is not regarded as cruel, merely as concerned to follow the accepted procedures for testing the safety of new products.

The nineteenth-century anti-cruelty movement was built on the assumption that the interests of non-human animals deserve protection only when serious human interests are not at stake. Animals remained very clearly 'lower creatures' whose interests must be sacrificed to our own in the event of conflict.

The significance of the new animal liberation movement is its challenge to this assumption. Taken in itself, say the animal liberationists, membership of the human species is not morally relevant. Other creatures on our planet also have interests. We have always assumed that we are justified in overriding their interests, but this bald assumption is simply species-selfishness. If we assert that to have rights one must be a member of the human race, and that is all there is to it, then what are we to say to the racist who contends that to have rights you have to be a member of the Caucasian race, and that is all there is to it? Conversely, once we agree that race is not, in itself, morally significant, how can species be? As Jeremy Bentham put it some 200 years ago:

The day may come when the rest of the animal creation may acquire those rights which never could have been withholden from them but by the hand of tyranny. The French have already discovered that the blackness of the skin is no reason why a human being should be abandoned without redress to the caprice of a tormentor. It may one day come to be recognized that the number of the legs, the villosity of the skin, or the termination of the os sacrum are reasons equally insufficient for abandoning a sensitive being to the same fate.

Someone might say: 'It is not because we are members of the human species that we are justified in overriding the interests of other animals; it is because we are rational and they are not.' Someone else might argue that it is because we are autonomous beings, or because we can use language, or because we are self-conscious, or because we have a sense of justice. All these contentions and more have been invoked to justify us in sacrificing the interests of other animals to our own.

One way of replying would be to consider whether non-human animals really do lack these allegedly important characteristics. The more we learn of some non-human animals, particularly chimpanzees but also many other species, the less able we are to defend the claim that we humans are unique because we are the only ones capable of reasoning, or of autonomous action or of the use of language, or because we possess a sense of justice. I shall not go into this reply here because it would take a long time and it would do nothing for the many species of animals who could not be said to meet whatever test was being proposed.

There is a much shorter rejoinder. Let us return to the passage I have quoted from Bentham, for he anticipated the objection. After dismissing the idea that number of legs, roughness of skin or fine details of bone formation should 'trace the insuperable line' between those who have moral standing and those who do not, Bentham goes on to ask what else might mark this boundary:

Is it the faculty of reason, or perhaps the faculty of discourse? But a full-grown horse or dog is beyond comparison a more rational, as well as a more conversable animal, than an infant of a day or a week or even a month, old. But suppose they were otherwise, what would it avail? The question is not, Can they reason? nor Can they talk? but, Can they suffer?

Bentham is clearly right. Whatever the test we propose as a means of separating human from non-human animals, it is plain that if all non-human animals are going to fail it, some humans will fail as well. Infants are neither rational nor autonomous. They do not use language and they do not possess a sense of justice. Are they therefore to be treated like non-human animals, to be fattened for the table, if we should fancy the taste of their flesh, or to be used to find out if some new shampoo will blister human eyeballs?

Ah, but infants, though not rational, autonomous or able to talk, have the potential to become adult humans — so the defender of human supremacy will reply to Bentham. The relevance of potential is another complicated argument that I shall avoid by the stratagem of focusing your attention on another class of humans who would fail the proposed test: those unfortunate enough to have been born with brain damage so severe that they will never be able to reason, or talk or do any of the other things that are often said to distinguish us from non-human animals. The fact that we do not use them as means to our ends indicates that we do not really see decisive moral significance in rationality, or autonomy, or language, or a sense of justice, or any of the other criteria said to distinguish us from other animals. Why do we lock up chimpanzees in appalling primate research centres and use them in experiments that range from the uncomfortable to the agonising and lethal, yet would never think of doing the same to a retarded human being at a much lower mental level? The only possible answer is that the chimpanzee, no matter how bright, is not human, while the retarded human, no matter how dull, is.

This is speciesism, pure and simple, and it is as indefensible as the most blatant racism. There is no ethical basis for elevating membership of one particular species into a morally crucial characteristic. From an ethical point of view, we all stand on an equal footing -whether we stand on two feet, or four, or none at all.

That is the crux of the philosophy of the animal liberation movement, but to forestall misunderstanding I had better say something immediately about this notion of equality.

It does not mean that animals have all the same rights as you and I have. Animal liberationists do not minimize the obvious differences between most members of our species and members of other species. The rights to vote, freedom of speech, freedom of worship — none of these can apply to other animals. Similarly, what harms humans may cause much less harm, or even no harm at all, to some animals. If I were to confine a herd of cows within the boundaries of the county of, say, Devon, I do not think I would be doing them any harm at all; if, on the other hand, I were to take a group of people and restrict them to the same county, I am sure many would protest that I had harmed them considerably, even if they were allowed to bring their families and friends, and notwithstanding the many undoubted attractions of that particular county. Humans have interests in mountain-climbing and skiing, in seeing the world and in sampling foreign cultures. Cows like lush pastures and shelter from harsh weather. Hence to deny humans the right to travel outside Devon would be to restrict their rights significantly; it would not be a significant restriction of the rights of cows.

Here is another example, more relevant to real problems about our treatment of animals. Suppose we decided to perform lethal scientific experiments on normal adult humans, kidnapped at random from public parks for this purpose. Soon every adult who entered a park would become fearful of being kidnapped. The resultant terror would be a form of suffering additional to whatever pain was involved in the experiments themselves. The same experiments carried out on non-human animals would cause less suffering overall, for the non-human animals would not have the same anticipatory dread. This does not mean, I hasten to add, that it is all right to experiment on animals as we please, but only that if the experiment is to be done at all, there is some reason, compatible with the equal consideration of interests, for preferring to use non-human animals rather than normal adult humans.

There is one point that needs to be added to this example. Nothing in it depends on the fact that normal adult humans are members of ~ our species. It is their capacity for knowledge of what may happen to them that is crucial. If they were not normal adults but severely brain-damaged humans - orphans perhaps, or children abandoned by their parents - then they would be in the same position as non-human animals at a similar mental level. If we use the argument I have put forward to justify experiments on non-human animals, we have to ask ourselves whether we are also prepared to allow similar experiments on human beings with a similar degree of awareness of what is happening to them. If we say that we will perform an experiment on monkeys but not on brain-damaged human orphans, we are giving preference to the humans just because they are members of our own species, which is a violation of the principle of equal consideration of interests.

In the example I have just given the superior mental powers of normal adult humans would make them suffer more. It is important to recognize that in other circumstances the non-human animal may suffer more because it cannot understand what is happening. If we capture a wild animal, intending to release it later, it may not be able to distinguish our relatively benign intentions from a threat to its life: general terror may be all it experiences.

The moral significances of taking life is more complex still. There is furious controversy about the circumstances in which it is legitimate to kill human beings, so it is no wonder that it should be difficult to decide whether non-human animals have any right to life. Here I would say, once again, that species in itself cannot make a difference. If it is wrong to take the life of a severely brain-damaged abandoned human infant, it must be equally wrong to take the life of a dog or a pig at a comparable mental level. On the other hand, perhaps it is not wrong to take the life of a brain-damaged human infant - after all, many people think such infants should be allowed to die, and an infant who is 'allowed to die' ends up just as dead as one that is killed. Indeed, one could argue that our readiness to put a hopelessly ill non-human animal out of its misery is the one and only respect in which we treat animals better than we treat people.

The influence of the Judeo-Christian insistence on the God-like nature of human beings is nowhere more apparent than in the standard Western doctrine of the sanctity of human life: a doctrine that puts the life of the most hopelessly and irreparably brain damaged human being — of the kind whose level of awareness is not underestimated by the term 'human vegetable' - above the life of a chimpanzee. The sole reason for this strange priority is, of course, the fact that the chimpanzee is not a member of our species, and the human vegetable is biologically human. This doctrine is now starting to be eroded by the acceptance of abortion, which is the killing of a being that is indisputably a member of the human species, and by the questioning of the value of applying all the power of modern medical technology to saving human life in all cases.

I think we will emerge from the present decade with a significantly different attitude towards the sanctity of human life, an attitude which considers the quality of the life at stake rather than the simple matter of whether the life is or is not that of a member of the species Homo sapiens. Once this happens, we shall be ready to take a much broader view of the wrongness of killing, one in which the capacities of the being in question will play a central role. Such a view will not discriminate on the basis of species alone but will still draw a distinction between the seriousness of killing beings with the mental capacities of normal human adults and killing beings who do not possess, and never have possessed, these mental capacities. It is not a bias in favour of our own species that leads us to think that there is greater moral significance in taking the life of a normal human than there is in taking the life of, for example, a fish. To give just one reason for this distinction, a normal human has hopes and plans for the future: to take the life of a normal human is therefore to cut off these plans and to prevent them from ever being fulfilled. Fish, I expect, do not have as clear a conception of themselves as beings with a past and a future. Consequently, to kill a fish is not to prevent the fulfillment of any plans, or at least not of any long-range future plans. This does not, I stress, mean that it is all right, or morally trivial, to kill fish. If fish are capable of enjoying their lives, as I believe they are, we do better when we let them continue to live than when we needlessly end their lives, though when we cut short the life of a fish, we are not doing something as bad as when we needlessly end the life of a normal human adult.

The animal liberation movement, therefore, is not saying that all lives are of equal worth or that all interests of humans and other animals are to be given equal weight, no matter what those interests may be. It is saying that where animals and humans have similar interests - we might take the interest in avoiding physical pain as an example, for it is an interest that humans clearly share with other animals — those interests are to be counted equally, with no automatic discount just because one of the beings is not human. A simple point, no doubt, but nevertheless part of a far-reaching ethical revolution.

This revolution is the culmination of a long line of ethical development. I cannot do better than quote the words of that splendid nineteenth century historian of ideas, W. E. H. Lecky. In his History of European Morals Lecky wrote: 'At one time the benevolent affections embrace merely the family, soon the circle expanding includes first a class, then a nation, then a coalition of nations, then all humanity, and finally, its influence is felt in the dealings of man with the animal world.' Lecky anticipated what the animal liberationists are now saying. In an earlier stage of our development most human groups held to a tribal ethic. Members of the tribe were protected, but people of other tribes could be robbed or killed as one pleased. Gradually the circle of protection expanded, but as recently as 150 years ago we did not include blacks. So African human beings could be captured, shipped to America and sold. In Australia white settlers regarded Aborigines as a pest and hunted them down, much as kangaroos are hunted down today. Just as we have progressed beyond the blatantly racist ethic of the era of slavery and colonialism, so we must now progress beyond the speciesist ethic of the era of factory farming, of the use of animals as mere research tools, of whaling, seal hunting, kangaroo slaughter and the destruction of wilderness. We must take the final step in expanding the circle of ethics. The essays which follow show how this can be done, both in theory and in practice.