In a recent issue of this journal, Kevin Corcoran has argued that the metaphysical theory one holds to about the nature of human persons is irrelevant to the sort of ethical questions that occupy bioethicists as well as the general public. Specifically, he argues that whether one holds a constitution view of human persons, an animalist view, or a substance dualist view, the real work in one’s ethical reasoning is done by certain moral principles rather than by metaphysical ones. I (...) raise objections to his analysis and propose that it is a combination of ethical principles and metaphysical principles that does the work in our judgements about the morality of abortion and other actions. (shrink)