In his paper "Why Abortion is Immoral", Don Marquis urges a reorientation of the abortion debate. Metaphysical issues concerning the personhood of fetuses, which previously held center stage in philosophical discussions of the morality of abortion, have proven to be intractable, he says. As long as the debate is left to rest on such issues, it will be at an impasse. In his view, we would do better to focus on a different question: does abortion cause harm, in particular, harm to the fetus? Once the debate is framed in these terms, he argues, it is clear that abortion is prima facie morally wrong, since abortion surely does harm the fetus, at least in the "standard" case.
But Marquis commits a crucial error. Although Marquis does not say so explicitly, he must assume that the question of harm is independent of the issue of personhood; otherwise, he could not hold that the latter was any more tractable than the former. As I shall argue here, however, that assumption is mistaken. We cannot get away from metaphysics so easily. My aim here is to show that, given certain widely held metaphysical views, including views about personal identity, his argument for the immorality of abortion rests on highly implausible premises. Marquis could, of course, reject the metaphysics. But that would be to concede that issues of personhood are of central importance, after all.