We argued in Chapter I that human beings are bodily beings, animal organisms, and that therefore they come to be when the human physical organism comes to be, do not cease to be until the human physical organism ceases to be, and so we cannot accurately regard our bodies as mere extrinsic tools. It may seem from this, however, that we are committed to physicalism – the view that human beings are purely physical entities (in the sense that there is no aspect of them that is not, or does not supervene upon, physical, material entities). It may seem that we are committed to the view that human beings are not different in kind from other animals, and that all animals, humans included, are simply the by-products of the blind shuffling of the simpler physical entities and forces.

But if this were true – that is, if human beings were only different in degree and not in kind from other animals, plants, molecules, and so on – then it would be hard to see any justification for holding that they are the kind of beings to whom we have any serious moral obligation to treat with full moral respect, for example, to treat as ends and never as mere means.

Moreover, some theists, in particular some philosophers of the Jewish, Christian, or Muslim heritages, may worry that the position defended in Chapter I closes the door to accepting such theologically based key propositions: man is created in the image of God, the human soul is immortal, and there is a resurrection of the body at the end of the world.