I find it strange that so many of my fellow libertarians and anarchists oppose and ridicule animal rights with such passion. For one thing, an animal right is perfectly libertarian in that it is a negative right. Unlike incoherent positive rights, such as the 'right' to education or health care, the animal right is, at bottom, a right to be left alone. It does not call for government to tax us in order to provide animals with food, shelter, and veterinary care. It only requires us to stop killing them and making them suffer. I can think of no other issue where the libertarian is arguing for a positive right'his right to make animals submit to any use he sees'and the other side is arguing for a negative right!

Nor is libertarianism inconsistent with animal rights, unless one is an exponent of contractarianism, an ethical theory riddled with problems. The nonaggression principle states that it is morally wrong to initiate force against others (or their property), except in self-defense. The question is whether this principle applies to animals. Are animals part of the 'moral community' that is covered by the nonaggression principle? In his recent essay 'Why Animal Rights Don't Exist,' Tibor Machan argues that animals cannot have rights, which is to say that the nonaggression principle cannot apply to animals. Does his argument succeed?

The Argument from Marginal Cases

For the rest of this essay, I will use 'animal rights' as a shorthand to denote the simple claim that animals have a single right: The right not to be made to die and suffer by humans except in self-defense. If you have problems with the concept of a 'right,' you can also think of this position as being equivalent to the following proposition: 'It is morally wrong to kill animals and make them suffer except in self-defense.' The most powerful argument for this conclusion is the Argument from Marginal Cases.

So-called 'marginal cases' are humans who lack the ability to reason or be held accountable for their actions but who are still considered part of the moral community and have a right not to be killed or made to suffer except in self-defense. (Philosophers also call such people moral patients.) This argument is so crucial to the animal rights debate that one philosopher, Daniel A. Dombrowski, has written a whole book about it called Babies and Beasts: The Argument from Marginal Cases.

I have never heard a satisfactory response to this stunning argument. It has convinced me'on a rational level'that it's morally wrong to kill animals or make them suffer except in self-defense. Pure Aristotelian logic powers the Argument from Marginal Cases. It demands simply that we treat like cases alike'or else cite a relevant difference between the cases. Here's how the Argument might work out in the course of a casual debate.

Opponent of animal rights: How can you say that animals have rights? It's impossible.

Proponent of animal rights: Why?

Opponent: For one thing, animals can't reason. They can't be held responsible for their actions. To have rights, you must have these capacities.

Proponent: Wait a minute. Infants can't reason. Does that mean it's open season on babies?

Opponent: Of course not. Infants will be able to reason someday. We must treat them as prospective rights-holders.

Proponent: But what if the infant is terminally ill and has only six months to live? What about a person who was born with part of his brain missing and has the mental capacity of a pig? What about a senile person? Is it OK to kill, eat, and otherwise use these people for our own ends, just as we now use pigs?

Opponent: Well . . . let me think about that.

Welcome to the Argument from Marginal Cases.

Given the revolutionary importance of this argument, I am shocked by the number of libertarians who ignore it when ridiculing animal rights. Maybe I shouldn't be surprised. It's a tough argument to deal with. Many times I have read an essay ridiculing animal rights and e-mailed the author to ask what his response is to the argument. Some of them respond, lamely, that being human is sufficient to have rights, period. Some dodge the issue. One or two authors admitted that they could not answer the argument, but they would not go so far as to agree flat-out that animals have the same rights as marginal humans.

Objectivists get especially excited when faced with the Argument from Marginal Cases. One time I e-mailed Edwin Locke, an Objectivist writer, in response to an essay he wrote ridiculing the notion of animal rights. Naturally, his essay made no mention of the Argument. When I explained it to him, Locke assured me that he had totally demolished the argument'in a recorded speech he gave several years earlier. If I wanted to hear it, he said, I should go to a Web site that sells Objectivist merchandise (he generously provided the link) and buy an audio tape of one of his talks. When I demanded to know why he couldn't just e-mail me his answer, he declared that he had no desire to talk with me further, that I had 'misrepresented' his views, and he was 'ending communication.' As you can see, the Argument from Marginal Cases has the power to really rattle people.

The Argument from Species Normality

That's why I respect Professor Machan. Not only does he bring up the Argument from Marginal Cases; he also tries to address it, however briefly. He even has the intellectual honesty to admit that it is 'the most telling point against' him. Does his rebuttal succeed? Here is the passage:

The most telling point against me goes as follows: "But there are people like very young kids, those in a coma, those with minimal mental powers, who also cannot be blamed, held responsible, etc., yet they have rights. Doesn't that show that other than human beings can have rights?"

This response doesn't recognize that classifications and ascriptions of capacities rely on the good sense of making certain generalizations. One way to show this is to recall that broken chairs, while they aren't any good to sit on, are still chairs, not monkeys or palm trees. Classifications are not something rigid but something reasonable. While there are some people who either for a little or longer while ' say when they're asleep or in a coma ' lack moral agency, in general people possess that capacity, whereas non-people don't. So it makes sense to understand them having rights so their capacity is respected and may be protected. This just doesn't work for other animals.

Machan seems to equivocate here. He starts out with the objection that includes people with 'minimal mental powers,' which includes people who are permanently deprived. But in his answer, he seems to shift to people who only temporarily lose their moral agency ('say when they're asleep or in a coma') and argues that we should 'understand them as having rights so their capacity is respected and may be protected.' But people who are permanently without moral agency have no such 'capacity.' Think of the senile, the congenitally retarded, the brain-damaged. These are the ones to whom the Argument from Marginal Cases applies. It does not apply to people who are asleep or in a coma from which they might someday awaken. Let us be clear about that.

How should we read Machan's broken-chair analogy? There is only one coherent way to interpret it. He is arguing that, just as a broken chair still belongs in the category of chairs, a marginal human still belongs in the category of humans. And because marginal humans belong to a species whose normal members can reason, have guilt, be held responsible for their actions'which Machan previously argued is a necessary condition for having any rights'the marginal members, too, deserve the same moral protections as those normal members. Here an implied premise lurks: Any member of a species most of whose members are moral agents has the same rights and protections as the normal members of that species. To put it more concisely: The moral status of an individual depends on what is normal for that individual's species. I will call this the Argument from Species Normality.

Why the Argument from Species Normality Fails

Does the Argument from Species Normality hold water? Does it destroy the Argument from Marginal Cases? The philosopher James Rachels addressed this argument in his essay ' Darwin , Species, and Morality':

This idea'that how individuals should be treated is determined by what is normal for their species'has a certain appeal, because it does seem to express our moral intuition about defective humans. 'We should not treat a person worse merely because he has been so unfortunate,' we might say about someone who has suffered brain damage. But the idea will not bear close inspection. Suppose (what is probably impossible) that a chimpanzee learned to read and speak English. And suppose he eventually was able to converse about science, literature, and morals. Finally he wants to attend university classes. Now there might be various arguments about whether to permit this, but suppose someone argued as follows: Only humans should be allowed to attend these classes. Humans can read, talk, and understand science. Chimps cannot.' But this chimp can do those things. 'Yes, but normal chimps cannot, and that is what matters.' Is this a good argument? Regardless of what other arguments might be persuasive, this one is weak. It assumes that we should determine how an individual is to be treated, not on the basis of its qualities, but on the basis of other individuals' qualities. This chimp is not permitted to do something that requires reading, despite the fact that he can read, because other chimps cannot. That seems not only unfair, but irrational. (p. 100, Animal Rights and Human Obligations, Tom Regan and Peter Singer, eds.).

Rachels's choice of a positive right'the 'right' to attend a university'is unfortunate, but his point applies to any kind of right. He gives us a straight reductio ad absurdum. The denial of rights for our super-smart chimp follows logically from Machan's implied premise that we should treat individuals according to what is normal for their species. If you think the outcome of Rachels's thought experiment is unacceptable or irrational, then you must also reject the claim that led you to it'that the moral status of a marginal human depends on what is normal for her species. Logically, you have no choice.

And why stop at rights? If an individual's moral status depends on what is normal for her species, why not impose the same moral duties on marginal cases? As Machan points out, an essential part of being a moral agent is that other people may hold you responsible for your actions. On the other hand, we do not hold those who lack moral agency responsible for their actions, for they do not know what they are doing. They are unable to have evil intent, or what lawyers call mens rea. But normal humans know what they are doing. Therefore, according to the Argument from Species Normality, we should punish even marginal humans for their bad actions. If, for example, a man suffering from the advanced stages of Alzheimer's escapes from a nursing home, steals a car, and runs over a child, we should convict him of manslaughter and throw him in the clink.

Are you willing to bite the bullet and accept these implications? Most people would say, 'Of course you shouldn't punish an insane man for his actions. You have to take into account his individual shortcomings. You can't treat him like a normal human.' Exactly. And that is why the Argument from Species Normality fails.

If you think about it, the Argument from Species Normality is very un-libertarian. It demands that we judge a being not as an individual, but as a member of a group, in this case her species. This is no different from the 'identity politics' we hear from the left. If it's senseless to decide a person's value or moral status solely on the basis of his race, it's equally senseless to decide a person's value or moral status solely on the basis of his species. Species, by itself, is simply not morally relevant. What matters is the nature of the individual, viewed under the light of objective moral principles.

It's easy to grasp this fact if you do some introspection and ask yourself why it is morally wrong to inflict suffering on a human who can't reason. Why is it morally wrong to torture an infant? Is it because she has the 'potential to become a moral agent'? Be honest about this. Isn't it really because the infant can suffer and has an interest in not suffering? Isn't it because forcing the infant to suffer against his will violates the nonaggression principle? Why is it immoral to use a victim of Alzheimer's for target practice? It is because he is 'a member of a species whose normal members can think conceptually and can be held responsible for their actions'? Surely not. It's because he can suffer, he has an interest in not suffering, and to treat him this way against his will goes against the nonaggression principle.

But all of this also holds true for a monkey. Like a 'marginal' human, the monkey can suffer. He has an interest in not suffering. To force him to die and suffer, except in self-defense, violates the nonaggression principle. It's a simple matter of treating like cases alike. Pure categorical logic.

Two Common Objections

Sometimes skeptics, including some libertarians, make the following objection to animal rights: 'If animals have a right not to be made to suffer, doesn't it follow that we should police the wilderness and prevent predatory animals from attacking their prey?' No, this does not follow. Animals should be allowed to defend themselves, of course, but they do not have a 'positive right' to protection any more than humans do. What the Argument from Marginal Cases proves, based on the logical requirement of treating like cases alike, is that it is immoral for moral agents to treat animals in ways we would not treat human marginal cases except in self-defense. Because animals are not moral agents, what they do is outside the purview of ethics. We might as well ask whether a zebra has a 'right' not to be crushed by a falling rock. As moral agents, we can only concern ourselves with what we should do and not do. Animals in the wild are on their own. At least an animal who is preyed upon in the wild has a fighting chance. It is not locked in a cage.

Another popular objection goes like this: 'But animals kill and eat each other in nature, so why shouldn't we be able to do the same thing?' In other words: 'If animals do it, then we can do it.' Surely it would be silly to base our moral principles on the actions of animals who can't even engage in moral reasoning! Some animals eat their offspring. Does that mean I am morally entitled to eat my offspring?

A valid question from an anarchist is, 'How would an animal's right be protected in an anarcho-capitalist world? Unlike a person, an animal can't pay a protection agency to protect it from aggression.' I plan to address this issue in a future essay. At any rate, before we worry about the practical matter of how to protect a right, we first have to settle the philosophical matter of whether that right exists in the first place.

Giving Animal Rights a Fair Shake

At the beginning of this essay I said I was surprised by the number of libertarians who ridicule animal rights while ignoring or evading the Argument from Marginal Cases. Not all libertarians fall into this category. At the FEE (Foundation for Economic Education) convention in 2002, I attended a talk by the great libertarian psychologist Nathaniel Branden. During the question and answer session, a young man told Branden that he maintained an Objectivist Web site. He had posted an essay ridiculing animal rights on the site. A woman had e-mailed him recently and challenged him with the Argument from Marginal Cases. He confessed that he could not think of a good retort.

Dr. Branden cut him off: 'I'm afraid I won't be able to help you on this.' Dr. Branden explained that he himself had 'struggled' with the question of the moral status animals. He said even Ayn Rand (a confirmed cat lover, by the way) had felt there must be something morally wrong with mistreating animals, but, unable to make it fit her Objectivist philosophy, she shelved the issue. As for him, he could not deny the pure Aristotelian logic of the Argument from Marginal Cases. He was stuck.

Other libertarians should follow Dr. Branden's example and face up to the merits of a reasoned animal rights position. Animal rights is not ridiculous. Animal rights is not inherently leftist. Just because the animal rights movement has been associated with the left does not make it inherently leftist like social security or socialized medicine. Leftists are also antiwar and against the Drug War. Does that mean we libertarians can't hold those positions without succumbing to leftist ideology? Of course not. Being for animal rights does not put you in the same category as a screaming animal rights protestor any more than being against the War in Iraq puts you in the same category as Michael Moore or the hyperemotional 'peace protesters' of San Francisco.

Someone once asked the anarchist Dr. Mary Ruwart whether libertarianism would allow for natural rights for animals. She gave this answer:

"The libertarian philosophy addresses relationships between human beings, not humans and other species. Many people are looking for a coherent way to address this issue, so please give some thought to developing one."

We libertarians are supposed to be the party of principle, the sticklers for logical consistency. It's time to put aside ad hominems and straw men. Let's take up Dr. Ruwart's challenge to address this issue with coherence and honesty. As a starting point, I encourage you to read Introduction to Animal Rights: Your Child or the Dog by Gary Francione. He offers a philosophy of animal rights that any libertarian can coherently endorse.