There exists a remarkable (albeit rare) creature that one is liable to encounter in the murkier corridors of political and moral philosophy -- namely the "pro-life" libertarian. This peculiar hybrid is a staunch defender of the purportedly non-perfectionist libertarian scheme of social organization while simultaneously arguing that foetal abortion is immoral and should be prohibited. It seems clear to me that these two ethical stances are incompatible and mutually exclusive, irrespective of their individual merit, if one is commited to rational coherence and consistency within a single framework of moral philosophy.
The ethical backbone of libertarianism is typically based on the notion of rights. Nozick, an influential champion of the minimal state, begins his magnum opus Anarchy, State and Utopia with the claim that "individuals have rights... so strong and far-reaching that they raise the question of what, if anything, the state and its officials may do". Nozick, like many libertarians before him, builds a political philosophy on the Lockean conception of rights, and concludes that anything beyond a night-watchman state charged with the protection of life, liberty and property is unwarranted. I take his views to be fairly representative of mainstream libertarians, although there are some who support an even more radical approach (e.g. Murray Rothbard and his 'propertarianism'). The arguments I will advance apply equally to any variant of libertarianism which postulates absolute property rights -- which, incidentally, amounts to more or less all of them.
Let me begin by saying that I am not a great admirer of the philosophical foundations upon which libertarianism is typically made to rest. The notion of natural rights is not entirely clear. What is the status of these rights, where do they come from and what makes them 'natural'? None of these questions have been plausibly answered. I am inclined to agree with Bentham that "right ... is the child of law; ... A natural right is a son that never had a father" and, furthermore, with his celeberated phrase that natural rights are little more than "nonsense upon stilts". For the purposes of this paper, however, I will assume that the libertarian natural rights framework is broadly speaking coherent, and subsequently hope to demonstrate that within this framework it is impossible, or at least extremely difficult, to defend the view that abortion is immoral and that it should be prohibited.
Before proceeding, it is also worth explicating what I take to be a "pro-life" stance towards abortion. I take it to be a view to the effect that aborting a human foetus is morally wrong under some (or all) circumstances. I include here all versions ranging from the moderate view, which admits "special" circumstances under which it is permissible (e.g. when the host's life is in danger, or cases of rape), to the radical view, which argues that abortion is always wrong irrespective of circumstances. As we shall see, both these versions (and anything in between them) are equally susceptible to my criticism when conjoined with a rights-based libertarian framework of morality.
Arguments against abortion are typically based on the sanctity of human life. At some stage in the process of development, the foetus is no longer to be regarded as a mere cluster of cells. The exact stage at which this occurs varies between ideologies. The current official Catholic doctrine, I believe, states that life begins at conception, while some maintain that it begins with the development of cognitive faculties. We need not concern ourselves with the finer points of this distinction. What concerns us is the fact that the "pro-lifers", as a whole, maintain that the foetus at some stage becomes a human being, and that as such, it should not be removed from the host -- it has a right to life and removal constitutes murder since the foetus cannot survive outside the womb. Consequently, abortion should be made a punishable criminal offence, as it violates the rights of the foetus.
Following this rough and ready sketch of the "pro-life" stance, I can state my thesis, which is the following: libertarianism and the "pro-life" stance are mutually incompatible, whatever form these two ideologies may take. The only stance on abortion compatible with libertarianism is an entirely permissive one -- for the libertarian, abortion must be permitted under any and all circumstances, on any pretext whatsoever.
The reason for this is to be found in the libertarian notion of property rights. Although the absolute property rights postulated by libertarians have been aggressively challenged, there seems to be a fairly widespread respect for the notion of self-ownership. The idea that we own ourselves has powerful intuitive appeal. Self-ownership, in this case, constitutes ownership over one's body and mind, at the very least, and there are some who argue that ownership over whatever one produces using body and mind follows naturally from this. The latter is hotly contested and I shall not waste time discussing it. My point is that self-ownership, and thus ownership of one's body, is a central theme in the entire spectrum of libertarian ideologies and is indispensable to all of them. Therefore, while the foetus may have a right to life, the impregnated mother also has rights -- amongst them absolute property ownership rights over her body. If we regard the foetus as a human being (with the rights that this supposedly entails), its presence in the womb constitutes an invasion of the host's property, i.e. her body. In the case of an unwanted pregnancy, then, the foetus is akin to a tenant that is to be evicted -- with the notable exception that the host's ownership claims on her body are arguably stronger than those of a landlord on his housing.
As we can see, there is a clash here between the foetal right to life and the host's property rights (i.e. self-ownership). This clash is analogous to that of a frostbitten traveller begging for shelter when death awaits out in the cold. If the traveller is refused shelter, he will die, whereas forcing the owner of the shelter to provide it to the traveller is a violation of his absolute property rights. Now, it may here be argued that when the right to life clashes with property rights, the former should take precedence. But this route is impossible for the libertarian. If he agrees with this, we may press him further. Do the starving and the dying then have a claim on other people's property? Is it legitimate to violate one person's property rights to help another? And if so, do we not have strong moral grounds for the much-despised and allegedly unjust welfare state? These are difficult questions to answer once the precedence of the right to life has been conceded. The pro-life libertarian must justify his opposition to abortion in some other way.
A second avenue is immediately open to him. He may maintain that the foetal right to life is a different sort of right -- the claim of the foetus on its host must differ from that of a starving man's claim on his fellow man. But wherein lies the difference? The only viable option is to maintain that the moral claims of the foetus on its host are greater and more extensive than those owed by any given human being to another. How can we defend this within the libertarian framework? Since obligations aside from those of non-interference can only arise contractually, we can do so only by arguing that the host has accepted certain contractual obligations by becoming pregnant. The act of becoming pregnant must therefore be understood as a contract to which the host is bound as a consequence of her actions. This solves our problem neatly -- the foetal right to life overrides the host's property rights because the host, by becoming pregnant, has agreed to suspend certain aspects of her rights of self-ownership throughout the course of foetal development.
The libertarian seems to have a solution here, but it is a costly one. For we may turn his own arguments against him. Just as the libertarian mocks and derides the "social contracts" of rival theories, we may look askance at his "foetal contract." What kind of contract can take place between a cluster of cells and its host? It is certainly not one to which the host or the foetus explicitly agree. Nor can the host be said to implicitly express consent -- the pregnancy may have been accidental and unwanted, or at the very least the host can make a plausible and irrefutable claim, after the fact, that this was indeed the case. And even if this were not the case, one cannot have a morally binding contract without the consent of all those which it immediately concerns. Plainly, the consent of the foetus is not forthcoming, and in the case of an unwanted pregnancy, the consent of the host is unlikely. To make matters worse, we cannot even defend this contract, in the style of Rawls, by arguing that it is one to which a rational human being would subscribe, for that is evidently not the case. Given the painfully unsubtle, skeletal moral framework of libertarianism, the whole notion can quickly be reduced to absurdity.
Since the property rights of the host cannot be made to give way without what the libertarian must concede is illegitimate coercion, the combination of libertarianism and a pro-life stance is bound to be paradoxical and indefensible. For just as granting the right to life precedence over property rights radically undermines a lodestone of libertarian ideology, so the postulation of an unspoken, unwritten and unhistorical contract opens the libertarian to charges of perfectionism -- i.e. the morally value-laden political conceptions supposedly anathema to him -- and thus lends credence to the arguments of his opponents.
It should be fairly clear that any composite variants of libertarianism and the "pro-life" stance are susceptible to the problems I have outlined. There remain few, if any, avenues open to the pro-life libertarian. If he wishes to be coherent, he must either give up his libertarianism or concede that abortion is always permissible.
05/02/2007 UPDATE: It has been pointed out to me that the critique above does not apply to utilitarian libertarians -- i.e. those who argue for libertarianism on the grounds of utility, as opposed to rights. I take it to be self-evident that libertarianism is incompatible with naive utilitarianism since there will obviously be individual cases where rights violation maximises utility. Rule utilitarianism is more accomodating, but as far as I know, no serious libertarian bases his beliefs on rule utilitarian foundation -- it is always supplemented by the notion of rights.