The world’s leading scholar in artificial intelligence once described people as machines made of meat. This nicely captures the consensus in the fields of psychology and neuroscience, which tell us that our mental lives are the products of our physical brains, and that these brains are shaped not by a divine creator, but by the blind process of natural selection.
But, with the exception of a small minority of philosophers and scientists, nobody takes this view seriously. It is offensive. It violates the tenets of every religion, and it conflicts with common sense. We do not feel, after all, that we are just material bodies, mere flesh. Instead, we occupy our bodies. We own them. We are spontaneously drawn to the view defended by René Descartes: We are natural-born dualists, so we see bodies and souls as separate.
This dualism has significant consequences for how we think, act, and feel. The philosopher Peter Singer discusses the notion of a moral circle – the circle of things that matter to us, that have moral significance. This circle can be very small, including just your kin and those with whom you interact on a daily basis, or it can be extremely broad, including all humans, but also fetuses, animals, plants, and even the earth itself. For most of us, the circle is mid-sized, and working out its precise boundaries – does it include stem cells, for instance? – can be a source of anguish and conflict.