I will conclude with some remarks about the rights of animals. When it is asked whether animals have rights, and whether human beings have duties to them, the question, I think, is partly moral and partly verbal. Let us consider the moral question first. This is the question whether the wrongness of cruelty to animals depends in part upon the animals' suffering, or whether it does not depend upon that at all, but only upon the bad effects upon human beings of cruelty to animals, and upon the badness of the human states of mind that such cruelty involves. (Hominum causa omne ius constitutum.) It is this latter view, I believe, that is in the minds of some of those who deny that animals have rights. Now most people would grant that it is wrong to bring about what is bad except in order to prevent worse. If this be so, then to say that the wrongness of cruelty to animals depends solely upon the human aspects of it, is to assume that the pain of animals is not bad. This could be either because no pain is bad, or because no animal pain is bad. This is not the place to discuss these propositions, but it is important to notice that the more inclusive or the less inclusive of them must be true if the wrongness of cruelty to animals depends entirely upon human beings or human society.
The question of words is whether to talk about the rights of animals is likely to mislead. If a legal right is an interest or expectation protected by law, then it follows that, under the Protection of Animals Act (1911), domestic and captive animals in England have rights, in that they are protected against being cruelly beaten, kicked, ill-treated, over-ridden, over-driven, over-loaded, tortured, infuriated, or terrified. Yet writers on jurisprudence say that animals do not have legal rights. Their main reason, I think, for not following their own logic, is that by saying that animals have legal rights they are putting them into a class all the other members of which are persons of one sort or another. Persons are beings with rights and duties, whereas no one supposes that animals have duties. Perhaps it is feared that the association of animals with this class in one respect will lead to suggestions that they share the other characteristics of its other members. Perhaps it is feared that the admission that animals have rights will be followed by claims that animals should be treated like persons in other ways also. Similar considerations, I suggest, apply when we ask whether it is proper to say that animals have moral rights. If we say they have, we class them with beings the rest of whom are capable of duties. Even congenital idiots look like men. Furthermore, although we say that animals have rights, we also think we are justified in hunting and eating them. This puts them into such a different category from other right-owning creatures, that we hesitate to apply the same word to the immunities we consider they are morally entitled to. Here, as elsewhere, the influence of what is nuclear and typical is unduly constraining.
(H. B. Acton, "Rights," The Aristotelian Society, supplementary volume 24 : 95-110, at 108-10 [italics in original; footnotes omitted])