Abortion is thought of as a contest between the rights of the mother and the rights of the unborn child. This is a mistake. The actual contest is between the mother and the father or whoever is advocating that the child be carried to term. It is just as much aggression to force a woman to bear a child she would rather not have inside of her body as it is against the child to abort it assuming that, ex post, it would not have wanted to be aborted were it allowed to live to the age where it could have a say in the matter.
After a certain point in the pregnancy, abortion only results in the death of the fetus as a matter of choice. This is where viability comes in. If the child is viable - meaning it would more likely live than die were it extracted in a non-destructive manner - then the choice of whether the child will be removed destructively or not may constitute aggression on the part of the mother against the interests of the father in the survival of his offspring. In this case, the father’s right to petition that the child be removed in a non-destructive manner ought to be acknowledged (assuming he was aware of the pregnancy… another separate issue altogether). However, prior to the point of viability, there doesn’t seem to be any way to balance the father’s interests in his potential offspring’s survival against the mother’s interest in controlling her own body without violating the interests of one or the other. Since a mother’s interest in materially controlling her own body clearly takes precedence over a father’s interest in the survival of his offspring which she is carrying, the mother should have plenary power to decide to abort.
Similarly, issues of child rearing and abuse should be analyzed as disputes between the potential guardians of the child, not necessarily as disputes between the child itself and its custodian/guardian. This will permit social/legal norms regarding what is permissible treatment of children to emerge in a way that preserves the natural interests of parents and other biological relatives of children in the health and welfare of those children.
There is no contest between the rights of the mother and the fetus because the fetus is simply incapable of asserting its rights. The root problem is that the fetus cannot speak for itself, so we cannot know its wishes or desires. Instead, the fetus has advocates - its father or grandparents, etc. In the case of disputed abortion, these advocates are in a dispute with the mother, it is the mother who will be coerced if a ruling is in favor of the advocates of the fetus and it is these advocates who will be restrained - by force, if necessary - from coercing the mother to continue the pregnancy if a ruling is in her favor. In this regard, a fetus is in the same position as any other entity on behalf of which people want to advocate, such as an animal. Rothbard says of animal rights (Ethics of Liberty):
“There is, in fact, rough justice in the common quip that “we will recognize the rights of animals whenever they petition for them.” The fact that animals can obviously not petition for their “rights” is part of their nature, and part of the reason why they are clearly not equivalent to, and do not possess the rights of, human being. And if it be protested that babies can’t petition either, the reply of course is that babies are future human adults, whereas animals obviously are not.”
Where I differ with Rothbard is that I think that animals likely would, in fact, have rights in a real natural order legal system for the same reasons that children and, to an extent, unborn fetuses would have rights - people are willing to fight for those rights. If you kick your dog, you are likely to end up in a dispute with someone who thinks you oughtn’t be mistreating the animal that way. The purpose of the law is to resolve disputes without martial contest and, unless this dispute is resolved by violence, it may have to be resolved through the legal system. That is, I may file suit against you for your treatment of your dog, seeking to seize the dog from you. Unlike human offspring, no one has any better claim to advocate for the dog than anyone else so there are no natural limitations on who may sue.
Fetuses and animals are in the same logical category, they are both mute entities. They are, therefore, incapable of participating in legal disputes and their rights, therefore, extend only so far as those who advocate on their behalf are willing to fight for them. To paraphrase Rothbard, “We will recognize the rights of unborn fetuses whenever they petition for them.” But fetuses would likely have rights in a real natural order legal system for precisely the same reason animals would likely have rights. That is, if you go to abort your fetus, you are likely to end up in a dispute with someone who believes you oughtn’t abort the fetus. Unlike in the case of a dog, however, there is a natural division between who has higher and lower claims to advocate for the well-being of the fetus, so not everyone may sue. I believe the point of viability would be a crucial dividing line in a natural order legal system.
To specifically answer your question, a mother drinking is not aggression against the fetus but it may be actionable by other family members who have an interest in the welfare of the child. Now, you might say that if the mother can abort the pregnancy without contest at any time before viability, then it is a moot point whether she drinks before viability but it’s not that simple. At each point in time, either the mother is intending to bring the child to term or she is not. If she is intending to bring the child to term, then abusive actions toward the fetus (such as drinking) are actionable. The mother can’t both claim that she intends to bring the child to term and that she doesn’t have to be concerned with the welfare of the fetus. So, if she chooses to abort, let her abort. If she will not abort it, then she can’t abuse the fetus without consequence. Other relatives of the fetus should have standing to sue the mother (of course, non-legal measures may be preferable/more effective).
Clayton -