Not all humans are rational, and not all humans are moral agents. The idea that a chimpanzee who is smarter than a mentally handicapped human should be treated worse than the human violates the thesis of moral individualism, which holds that individuals should be treated according to their own characteristics. I’m surprised that you, as an avowed libertarian, would reject moral individualism and opt for irrationally basing moral status on arbitrarily assigned group membership.
http://homepage.uab.edu/nnobis/papers/cohen-kind.html

Firstly, what criteria are you using to judge “sapience” with? The ability to reason? The ability to feel pain or to feel emotion? The ability to be self aware? The ability to make moral judgements? I have heard several definitions of sapience, and I can’t tell from the article which one you’re using when you claim that “sapience” is the one characteristic that determines whether a creature is assigned “natural rights”.

Secondly, as far as I can see, sapience (like intelligence) is not an all-or-nothing thing. No matter what definition of sapience you use, there must be different degrees of sapience. Some animals, such as the great apes, seem to display both intelligence and the first glimmerings of sapience (not surprising when you consider that they are our close evolutionary relatives). On the other hand, some reasonably intelligent humans are rather ammoral – as an extreme example, think of sociopaths. Does a sociopath have no “natural rights”? Do animals with some degree of “sapience” deserve more consideration than non-sapient animals? Do people with more “sapience” have more “natural rights” than less or non-sapient people? If not, why not?

Thirdly, how does your theory work for intellectually disabled people? Moderately mentally disabled humans are partially functioning humans – they are not vegetables, but they often have little or no concept of morality, and sometimes have no more intelligence or sapience than a chimpanzee. Why should we grant these people “natural rights” if they are non sapient?

Saying that these people get rights simply because they’re in the same species as the rest of us sapient humans seems more than a little circular. If we’re basing our assessment of whether a creature has natural rights on whether that creature is sapient, then it would seem to be rather irrelevant what species the creature is. All we should be assessing is whether the creature is sapient, and if so, to what degree. A non-sapient human surely shouldn’t be treated any differently to a non-sapient dog, horse or chicken, since like these animals, it is not a moral agent. According to your article, I should therefore be able to do whatever I please to a mentally disabled human, my only consideration being what the rest of society might think of me.

Alternatively, if you propose granting non-sapient creature natural rights simply because most of their con-specifics are “sapient”, then how do you defend this logically? The fact that a non-sapient creature belongs to the same species as a sapient creature does not make the first creature any more of a moral agent. Plus, how would you determine whether a partially sapient species deserves to have “natural rights”? If we ever discover an alien species that is on the evolutionary verge of sapience, then what percentage of that species would need to be “sapient” before you would accord them all “natural rights”?

Craig, I absolutely agree that families should never overrule the decisions of deceased/braindead family members. In the presence of a will or other statement, of course those wishes should be followed.

When I wrote this post, I actually had in mind an example where a person was born without any neurological function and so would never have been able to write such a will in the first place.

It is the persons wishes that are important, not the families.

While a person is alive, they possess rights over their own body. When they die, what makes these rights “transfer” to the persons’ family? This is the kind of thinking that allows families to overturn the decisions of people adamant on organ donation – what gives them this right?

I think it’s BS that a family might “own” their relatives’ bodies – There is no reason for a previously capable persons’ rights to transfer to anyone else, without their express consent (e.g. will, power of attorney).

You disbelieve in divinity, yet you believe in morality. You believe in the existence of moral agents, moral duties and moral rights (and, furthermore, “natural” rights as opposed to mere “socially constructed” rights). But there is no evidence for any of these, so it is foolish to postulate them.

Before you defend your claim that there really is a moral realm, consider what general kind of thing would count as evidence for the existence of a divine realm. In the light of those considerations, consider what general kind of thing would count as evidence for the existence of moral rights and responsibilities, etc. Then cite some actual evidence. I won’t hold my breath.

You believe that humans are categorically exceptional as compared to other animals, on the grounds of sapience. It’s instructive to read what Wikipedia says about Linnaeus, who named us homo sapiens.

Strangely, it seems that he did not consider the idea whether humans were just another kind of animal when choosing this name, instead basing his selection on contemperorarily [sic] deep religious convictions that man was a product of special creation. Thus, his chosen biological name was intended to emphasize man’s uniqueness and separation from the rest of the animal kingdom.

It seems that the very name of our species is question-begging! We may be exceptional, but we are not categorically exceptional. We’re not unique, just at one end of the spectrum.

The foundations of our belief that we are special were swept away in 1859. Yet our ignorance and arrogance are such that the belief that we are special has not crumbled. Evidence that we are still in the grip of theistic, pre-1859 belief systems is everywhere, including this blog post. For example, you ask, “Why are humans categorically exceptional as compared to animals?” when surely you mean to ask, “Why are humans categorically exceptional as compared to other (non-human) animals?”. The only thing we can be when compared to ourselves is the same. There are libertarians elsewhere who are happy to categorically deny even that we are animals, thereby denying one of the fundamental tenets of modern biology.

You haven’t said much about the foundations of morality, but what I glean from your post and your link to the Wikipedia article on moral agency is that you think that humans have moral rights and responsibilities on account of their membership of a group, some of whose members are sapient. You think that morality is based on our rationality, and our consequent ability to form self-interested judgments and enter into social contract type arrangements with other rational, self-interested beings.

A social contract is not worth the paper it’s not written on, and cannot be the basis of morality (even supposing morality has a basis). And if it was, it would not allow you to distinguish between the so-called natural rights of humans and the “socially constructed” rights of animals, since according to contractarianism, both types of rights arise in the same way – by being granted to the rights-holders by social convention.