The philosopher Peter Singer has coined the word ‘speciesism’ to describe a prejudice or attitude of bias towards the interests of members of one’s own species and against those of members of other species. The fundamental objections to speciesism apply equally to racism and sexism.
Now many philosophers have proposed the principle of equal consideration of interests, in some form or other, as a basic moral principle; but not many of them have recognized that this principle applies to members of other species as well as to our own. Jeremy Bentham was one of the few who did realize this. In a forward-looking passage, written at a time when black slaves in the British dominions were still being treated much as we now treat nonhuman animals, Bentham wrote:
The day may come when the rest of the animal creation may acquire those rights, which never could have been witholden 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. What else is it that should trace the insuperable line? 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?
Here Bentham points to the capacity for suffering as the vital characteristic that gives a being the right to equal consideration. The capacity for suffering—or more strictly, for suffering and/or enjoyment or happiness—is not just another characteristic like the capacity for language, or for higher mathematics. The capacity for suffering and enjoying things is a prerequisite for having any interests at all, a condition that must be satisfied before we can speak of interests in any meaningful way. It would be nonsense to say that it was not in the interests of a stone to be kicked along the road by a schoolboy. A stone does not have interests because it cannot suffer. Nothing that we can do to it could possibly make any difference to its welfare. A mouse, on the other hand, does have an interest in not being tormented, because it will suffer if it is.
The point is, if a being suffers, there can be no moral justification for refusing to take that suffering seriously. No matter what the nature of the being, the principle of equality requires that its suffering be counted equally with the like suffering—in so far as rough comparisons can be made—of any other being. If a being is not capable of suffering, or of experiencing enjoyment or happiness, there is nothing to be taken into account. This is why the limit of sentience (using the term as shorthand for the capacity to suffer or experience enjoyment or happiness) is the only defensible boundary of concern for the interests of others.
The racist violates the principle of equality by giving greater weight to the interests of members of his own race, when there is a clash between such interests and the interests of those of another race. Similarly the speciesist allows the interests of his own species to override the greater interests of members of other species. The pattern is the same in each case.
Except that most human beings are speciesists
For the great majority of human beings, especially in urban, industrialized societies, the most direct form of contact with members of other species is at mealtimes: we eat them. In doing so we treat them purely as means to our ends. We regard their life and well-being as subordinate to our taste for a particular kind of dish. I say "taste" deliberately because it is purely a matter of pleasing our palate. There can be no defense of eating flesh in terms of satisfying nutritional needs, since it has been established beyond doubt that we could satisfy our need for protein and other essential nutrients far more efficiently with a diet that replaced animal flesh by soy beans, or products derived from soy beans, and other high-protein vegetable products.
It is not merely the act of killing that indicates what we are ready to do to other species in order to gratify our tastes. The suffering we inflict on the animals while they are alive is perhaps an even clearer indication of our speciesism than the fact that we are prepared to kill them. In order to have meat on the table at a price that people can afford, our society tolerates methods of meat production that confine sentient animals in cramped, unsuitable conditions for the entire durations of their lives. Animals are treated like machines that convert fodder into flesh, and any innovation that results in a higher "conversion ratio" is liable to be adopted. As one authority on the subject has said, "cruelty is acknowledged only when profitability ceases."
Since, as l have said, none of these practices cater for anything more than our pleasures of taste, our practice of rearing and killing other animals in order to eat them is a clear instance of the sacrifice of the most important interests of other beings in order to satisfy trivial interests of our own. I do not myself think there is any other way to avoid speciesism but to stop this practice. It may be difficult, but it is no more difficult than it would have been say for a white slaveholder to go against the traditions of his society and free his slaves: if we do not change our dietary habits, how can we censure those slaveholders who would not change their own way of living? There is a related but not identical argument to be had about animal experiments, another major form of speciesism in our society.