When does a person begin?

According to the Constitution View of persons, a human person is wholly constituted by (but not identical to) a human organism. This view does justice both to our similarities to other animals and to our uniqueness. As a proponent of the Constitution View, I defend the thesis that the coming-into-existence of a human person is not simply a matter of the coming-into-existence of an organism, even if that organism ultimately comes to constitute a person. Marshalling some support from developmental psychology, I give a broadly materialistic account of the coming-into-existence of a human person. I argue for the metaphysical superiority of the Constitution View to Biological Animalism, Thomistic Animalism, and other forms of Substance Dualism. I conclude by discussing the single implication of the Constitution View for thinking about abortion. Footnotesa Thanks to Gareth Matthews and Catherine E. Rudder for comments. I am also grateful to other contributors to this volume, especially Robert A. Wilson, Marya Schechtman, David Oderberg, Stephen Braude, and John Finnis.