This is the 48th post in my Theories of Knowledge and Reality series. The last post looked at some arguments roughly based on Rene Descartes' arguments for dualism. This post considers a very different sort of argument for dualism from Gottfried Leibniz.
Leibniz asks us to imagine walking around inside a large mill or factory. If we are merely physical, then a tiny person walking around inside your brain would be seeing the same sorts of things you see when walking around the mill. There are physical things going on, things we understand through science. We know exactly what those things involve, and they don't involve thinking. Why, then, should we think a physical organ like a brain involves thinking? So dualism must be true. The main intuition behind this is that physical processes don't seem to explain how thinking can come about. It seems too mysterious for a physical brain to explain.
If the simplest theory explaining the evidence is probably the best, then a theory without all that extra mind stuff is better than one without it, given that they both assume the physical world exists. Leibniz thinks he avoids this, since he claims materialism doesn't explain thinking. He says you need to go beyond the physical world to explain thinking. If so, then dualism is necessary to explain something. The principle of simplicity applies only if you've got two theories that equally explain the evidence, but if dualism explains it better, then go with that.
Materialists reply that he hasn't explained anything. He's said physical things don't explain thinking, but he hasn't said how immaterial minds do any better. What is this immaterial mind thing supposed to be, and how does it explain thinking any better than physical processes? The physical processes may lead to thinking. It's sort of mysterious how they'd do that, but that doesn't mean they don't. Dualism hasn't added anything like an explanation, just the claim that something else is needed. So has the dualist really explained anything? If not, the materialist says, then the simplicity principle tells us to be materialists. Materialism hasn't explained all the evidence, but dualism doesn't do any better, so they're on equal footing in terms of explanations. Then we go with the one without the extra souls, and we hold to the materialist view.
(Keep in mind that the story gets complicated if you include George Berkeley's idealist view, which denies the existence of anything beyond our minds. According to his view, the world is also simpler than dualism, since only minds exist and not external physical objects. In terms of simplicity, this view is as good as physicalism/materialism.)objects. In terms of simplicity, this view is as good as physicalism/materialism.)
So far it looks as if the traditional arguments for dualism from such noted figures as Descartes and Leibniz are good at expressing intuitions that dualists have but not as helpful in offering reasons for materialists to abandon materialism.In the next post, I'll start looking at one of the strongest arguments against dualism to see if the arguments for materialism are any better.