According to a great many philosophers and jurisprudents, animals do not have rights for the simple reason that they are not the kinds of beings who can have rights. We can have duties concerning animals, these writers are often quick to add, but those duties are not owed to the animals as their due, and thus cannot be claimed against us as rights. Animals in this respect are like trees and rocks, automobiles and buildings, which are not the sorts of things of which it even makes sense to say they could have rights of their own. In respect to having rights, animals are more like pebbles and sunbeams than they are like full-fledged human beings. I believe that this view of the moral status of animals is radically mistaken, not because its distinguished proponents are somehow misinformed about the facts or insensitive in their attitudes, but rather because they misunderstand the basic terms of their own moral vocabulary even as applied to human beings.
(Joel Feinberg, "Human Duties and Animal Rights," chap. 9 in his Rights, Justice, and the Bounds of Liberty: Essays in Social Philosophy [Princeton: Princeton University Press, 1980], 185-206, at 186-7 [italics in original; endnotes omitted] [essay first published in 1978])
Note from KBJ: It may surprise you to learn that much of the debate about animal rights among philosophers has been about whether animals can have rights. If they do have rights, then obviously they can have rights; but it doesn't follow from the fact that they can have rights that they do have rights. Philosophers, as such, are equipped to answer logical or conceptual questions about animal rights, but not factual or normative questions. This is not to say that philosophers cannot answer factual and normative questions. It is to say that when they do answer such questions, they do so in a nonphilosophical capacity. Why does this matter? Because philosophical expertise, like any sort of expertise, is limited. Being expert in logic or conceptual analysis does not make one an expert on factual or normative matters.