"I will argue that animals have no basic rights to life, liberty, or property... the concept of “rights” is inapplicable to considerations of how animals ought to be treated... Rights and liberty are political concepts applicable to human beings because human beings are moral agents, in need of what philosopher Robert Nozick called “moral space,” that is, a definite sphere of moral jurisdiction where their authority to act is respected and protected so that it is they, not intruders, who govern themselves and either succeed or fail in their moral tasks...
Oddly, it is clearly admitted by most animal rights or liberation theorists that only human beings are moral agents—for example, they never urge animals to behave morally (by, for example, standing up for their rights by leading a polit-ical revolution). No animal rights theorist proposes that animals be tried for crimes and blamed for moral wrongs. If it is true that the moral nature of human beings gives rise to the conception of basic rights and liberties, then by this alone, animal rights and liberation theorists have made a fatal admission in their case...
I recall that when a young boy once tried out an air gun by shooting a pigeon sitting on a telephone wire before the apartment house in which he lived, there was no end of rebuke in response to this wanton callousness. Yet those who rebuked the boy were not implying that “we must view our entire history as well as all aspects of our daily lives from a new perspective.” Rather, they seemed to understand that reckless disregard for the life or well-being of animals shows a defect of character, lack of sensitivity, callousness—without denying, at the same time, that numerous human purposes justify our killing animals and using them in the various benign ways they have been used throughout human history...
One reason for the propriety of our use of animals is that we are more important or valuable than other animals and some of our projects may require the use, even killing, of animals so as to succeed. Notice that this is different from saying that human beings are “uniquely important”...
That there are things of different degree of value in nature is admitted by animal rights advocates, so there is no need to argue about that here. When they insist that we treat animals differently from the way we treat, say, rocks—so that we may use rocks in ways that we may not use animals—animal rights or liberation champions testify, at least by implication, that animals are more important than rocks...
There simply is evidence through the natural world of the existence of beings of greater complexity and of higher value. For example, while it makes no sense to evaluate as good or bad such things as planets or rocks or pebbles—except as they may relate to human purposes—when it comes to plants and animals, the process of evaluation commences very naturally indeed. We can speak of better or worse oaks, redwoods, zebras, foxes, or chimps... Indeed, none are more ready to testify to this than animal rights advocates, who, after all, do not demand any change of behavior on the part of nonhuman animals and yet insist that human beings conform to certain moral edicts as a matter of their own choice. This means that even animal rights advocates admit outright that to the best of our knowledge, it is with human beings that the idea of moral responsibility enters the universe...
Where do individual human rights come into this picture? The rights being talked of in connection with human beings have as their source, as noted earlier, the human capacity to make moral choices. We have the rights to life, liberty, and property—as well as more specialized rights connected with politics, the press, religion, and so forth—because we have as our central task in life to act morally...
We have seen that the most sensible and influential doctrine of human rights rests on the fact that human beings are indeed members of a discernibly different species, in which the members have a moral life to aspire to and must have principles upheld for them in communities that make their aspiration possible. Now, there is plainly no valid intellectual place for rights in the nonhuman world, the world in which moral responsibility is for all practical purposes absent...
In his book The Difference of Man and the Difference It Makes, Mortimer Adler undertakes the painstaking task of showing that even with the full acknowledgment of the merits of Darwinian and, especially, post-Darwinian evolutionary theory, there is ample reason to uphold the doctrine of species distinction—a distinction, incidentally, that is actually presupposed within Darwin’s own work. Adler shows that although the theistic doctrine of radical species differences is incompatible with current evolutionary theory, the more naturalistic view that species are superficially (but not negligibly) different is indeed necessary to the theory. The fact of occasional borderline cases is simply irrelevant—what is crucial is the generalization that human beings are basically different from other animals, by virtue of “a crucial threshold in a continuum of degrees.”...
The fact is that with the emergence of the human species, a new problem arose in nature—basic choices that other animals do not have to confront had to be confronted. The question “How should I live?” faces each human being. And that is what makes it unavoidable for human beings to dwell on moral issues and to see other human beings as having the same problem to solve, the same question to dwell on. For this reason we are very different from other animals—we do terrible, horrible, awful things to each other and to nature, but we can also do much, much better and achieve incredible feats nothing else in nature can come close to.
Indeed, then, the moral life is the exclusive province of human beings, so far as we can tell for now. Other—lower(!)—animals simply cannot be accorded the kind of treatment that such a moral life demands, namely, respect for and protection of basic rights to life, liberty, and property...
Humane treatment, compassion, lack of cruelty, and similar moral concepts will have to be developed for our adequate understanding of how animals ought to be treated by human beings. When enlisted to handle this area of our moral concerns, the concept of rights simply cannot be made use of smoothly enough without watering it down as a clear concept within politics and law...
As far as we can tell, no animal raises the question of whether animals are thinking beings. Animals, furthermore, appear to have no central, crucial need of thinking, whereas without thinking, human beings cannot begin to survive. Thinking for us is the mode of survival and flourishing—we cannot count on our instincts to get on with our lives. Other animals, in contrast, can handle their lives by means of their instincts, and for them their minimal abstract thinking is an aside, brought on usually by human beings, scientists who induce thinking in them while they are in captivity. From this we can conclude, sensibly, that it is valid to conclude that human beings are rational animals. That is what distinguishes us from other living things."
--- Classical Individualism: The Supreme Importance of Each Human Being / Tibor R. Machan
Of course, this raises the question on if humans who cannot think or make choices have rights