So far McCloskey is on solid ground, but one can quarrel with his denial that any animals but humans have interests. I should think that the trustee of funds willed to a dog or cat is more than a mere custodian of the animal he protects. Rather his job is to look out for the interests of the animal and make sure no one denies it its due. The animal itself is the beneficiary of his dutiful services. Many of the higher animals at least have appetites, conative urges, and rudimentary purposes, the integrated satisfaction of which constitutes their welfare or good. We can, of course, with consistency treat animals as mere pests and deny that they have any rights; for most animals, especially those of the lower orders, we have no choice but to do so. But it seems to me, nevertheless, that in general, animals are among the sorts of beings of whom rights can meaningfully be predicated and denied.
Now, if a person agrees with the conclusion of the argument thus far, that animals are the sorts of beings that can have rights, and further, if he accepts the moral judgment that we ought to be kind to animals, only one further premise is needed to yield the conclusion that some animals do in fact have rights. We must now ask ourselves for whose sake ought we to treat (some) animals with consideration and humaneness? If we conceive our duty to be one of obedience to authority, or to one's own conscience merely, or one of consideration for tender human sensibilities only, then we might still deny that animals have rights, even though we admit that they are the kinds of beings that can have rights. But if we hold not only that we ought to treat animals humanely but also that we should do so for the animals' own sake, that such treatment is something we owe animals as their due, something that can be claimed for them, something the withholding of which would be an injustice and a wrong, and not merely a harm, then it follows that we do ascribe rights to animals. I suspect that the moral judgments most of us make about animals do pass these phenomenological tests, so that most of us do believe that animals have rights, but are reluctant to say so because of the conceptual confusions about the notion of a right that I have attempted to dispel above.
(Joel Feinberg, "The Rights of Animals and Unborn Generations," chap. 8 in his Rights, Justice, and the Bounds of Liberty: Essays in Social Philosophy [Princeton: Princeton University Press, 1980], 159-84, at 166-7 [italics in original] [essay first published in 1974])