One common approach to restricting abortion is to push the time limit ever closer to conception.  One moral argument for this is based on the claim that at a specific time the fetus has qualities that grant it a moral status such that killing it is immoral. While some claim this moment is conception, most find this implausible since a single cell lacks qualities that could confer a suitable moral status.

From a moral and pragmatic standpoint, it makes more sense to select a time when the fetus has qualities that are intuitively relevant to its moral status. These include such qualities as being able to feel pain, the ability to respond to stimuli and presenting other evidence of mental activity. While political opponents of abortion rarely advance philosophically rigorous arguments, the case is easy enough to make. One obvious approach is utilitarian: the fetus’ capacity to suffer means it counts in the moral calculation of abortion. The o problem with this approach is that the fetus has far less capacity than the mother and thus her interests would always seem to outweigh those of the fetus. This is analogous to similar arguments about the treatment of animals: if the woman’s interests outweigh those of a fetus that can feel pain, then the same would hold true when the interest of a human conflicts with that of an animal. If the utilitarian approach is adopted to argue in defense of fetuses, then moral consistency would require that the same argument be applied to animals with qualities equal to (or greater than) those possessed by a fetus. This would include many animals that are used for food, such as chickens, cows and pigs. As such, if abortion should be restricted based on the qualities of the fetus, then the killing of animals also be restricted. If abortion should be legally restricted on these moral grounds, then vegetarianism should also be imposed by law. That said, consistency seems to be of n concern in politics. While utilitarianism does have considerable appeal, there are alternatives.

A common alternative to utilitarianism is deontology, the view that actions are inherently right or wrong regardless of the consequences. On this view, killing a being that has the right sort of moral status would always be wrong and utilitarian calculations are irrelevant. So, if the fetus has the right sort of status at a specific stage of development, then it would be wrong to kill the fetus. As with the utilitarian argument, this would seem to open the moral door for animals as well. For example, if the capacity to feel pain grants the fetus a moral status that forbids killing it and justifies legally restricting abortion, then animals that feel pain must also be granted the same status and legal protection. Put roughly, if abortion should be restricted because fetuses feel pain, then meat consumption should be restricted because animals feel pain. Any arguments advanced involving painless killing of animals to morally justify meat consumption would also justify painless abortion. Obviously enough, moral arguments that contend that it is acceptable to kill animals because they are inferior to us would also apply to developing fetuses.

It must be noted that the above discussion is focused on moral arguments involving the claim that the fetus has moral status because it has certain empirically testable qualities, such as the capacity to feel pain. While arguments based on non-empirical qualities (such arguments based on the soul) can be advanced, they would take the discussion beyond ethics and into metaphysics. That said, there does seem to be an obvious way to restrict abortion based on empirical qualities while consistently avoiding extending the same legal protection to animals.

Fetuses are, obviously enough, biologically human. Thus, it could be argued that this is the key moral difference between humans and animals that would justify restricting abortion while still allowing animals to be used as food. One problem with this approach is that if being human is what matters, then appeals to other qualities are irrelevant. So, the argument should simply be that killing humans is wrong, fetuses are human, so killing them is wrong. While this is an option, it does abandon the appeal to qualities argument. This is an approach that some anti-abortion people use; although they also use the qualities argument as a persuasive device (even when they would not apply it to animals).

It could be argued that it is a combination of being human and the other relevant qualities that give the fetus its special status—this would allow for abortion before the fetus has those qualities while also denying animals with those qualities an analogous moral status. The challenge is showing what it is about being human that makes the moral difference. While humans are humans, it can also be said that cows are cows and the question remains as to what it is about being human that makes the moral difference. If it is a quality, then that quality can be pointed to. If it is mere species membership, then that seems utterly arbitrary and unprincipled—mere speciesism. As such, it would seem that any arguments designed to restrict abortion based on the empirical qualities of fetuses would also apply to animals possessing equal or greater qualities. If the legal restriction of abortion based on the appeal to qualities is justified, the same justification would require legal restrictions on killing animals. Roughly put, legally restricting abortion in a consistent way would effectively require legally mandating vegetarianism.