When debating the permissibility of abortion, conservatives tend to argue that killing innocent humans is wrong, fetuses are innocent human beings, and therefore killing fetuses is wrong. In response, liberals tend to attack the premise that fetuses are human beings. The focus of the abortion debate thus tends to be on the location of the line between a fetus as a bundle of cells and a fetus as an unborn human child.
I’ve been reading through Peter Singer’s Practical Ethics, and he offers an interesting take on the abortion debate that sidesteps the usual abortion debate sticking point. Singer’s position on abortion follows fairly straightforwardly from his well known argument about the ethical treatment of animals. There is no intelligible distinction, Singer claims, that justifies allowing a being’s species to determine the being’s moral standing. Most attempts to draw this distinction run into trouble when it comes to children and the mentally disabled. For example, Aristotle argued that what distinguishes humans from animals is the unique human capacity to reason. However, children and some mentally disabled people have reasoning abilities that are similar to those of some animals. Therefore, this distinction, and others like it, fail, because they judge that (counter to our intuitions) some children and mentally disabled people do not qualify as fully human.
So if there is no intelligible morally significant distinction between human and non-human, then the dividing line between a fetus as a bundle of cells versus a fetus as a full human in the abortion debate loses its importance. Instead, Singer proposes giving fetuses, depending on how developed they are, the same moral standing that we would give to animals with similar capacities to experience pain.
This seems closer to being right to me than any other stance on abortion that I’m aware of.