Other animals, which, on account of their interests having been neglected by the insensibility of the ancient jurists, stand degraded into the class of things. [original emphasis] … The day has been, I grieve it to say in many places it is not yet past, in which the greater part of the species, under the denomination of slaves, have been treated … upon the same footing as … animals are still. 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 skin is no reason why a human being should be abandoned without redress to the caprice of a tormentor. It may come one day to be recognized, that the number of 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 for discourse?…the question is not, Can they reason? nor, Can they talk? but, Can they suffer? (Bentham 1781)
Contemporary utilitarians, such as Peter Singer (1990, 1993), suggest that there is no morally justifiable way to exclude from moral consideration non-humans or non-persons who can clearly suffer. Any being that has an interest in not suffering deserves to have that interest taken into account. And a non-human who acts to avoid pain can be thought to have just such an interest. Even contemporary Kantians have acknowledged the moral force of the experience of pain. Korsgaard, for example, writes “it is a pain to be in pain. And that is not a trivial fact” (1996, 154).
When you pity a suffering animal, it is because you are perceiving a reason. An animal’s cries express pain, and they mean that there is a reason, a reason to change its conditions. And you can no more hear the cries of an animal as mere noise than you can the words of a person. Another animal can obligate you in exactly the same way another person can. …So of course we have obligations to animals. (Korsgaard, 1996, 153)
When we encounter an animal in pain we recognize their claim on us, and thus beings who can suffer are morally considerable.