Following my last post, I want to explore the claim that substance dualism — the view that we’re made of two separate substances (a nonphysical “soul” and a physical body) — can avoid the problems raised against determinism.

Some religious apologists claim that because the soul is not made of physical stuff, it is not determined in what it believes, wills, or chooses to do. The soul is said to animate the body, store our memories, and causes our actions. But because it is not physically determined, it escapes the problems raised against the materialist and physicalist views of brains and minds. The soul, it is argued, allows each of us to act as a “prime movers unmoved”; we can cause certain events to happen, and nothing — or no one — causes us to cause those events to happen.[1]

But how sensible is such a claim? It seems to me that even if we posit an immaterial soul that uses the brain and sense organs as its point of contact with the world, any reliably produced information it obtains will still be causally determined. The only alternative to determinism is indeterminism. That is, rejecting the idea that the soul’s input information and output commands are causally determined leaves one only to say that both lack any sort of antecedent causes. But it seems this would cut a person off from having informed beliefs, memories, and actions — the soul would be blind to the world.

Let us consider that we have a soul; an immaterial substance that interacts with the body. How could we infer things about the world? How could we come to form the belief that, say, throwing a rock at a window will break it? Imagine that a curious child picks up a rock and hurls it at a glass window — *SMASH* the window shatters. Certain images will form on the child’s retinas, and certain sound waves will penetrate the child’s ears — these are physically determined effects caused by the shattering glass. It seems to me that the soul theory would go as follows: the sensory information is taken in and transferred through the brain into the soul, where it is stored and made sense of (these are the inputs). And it is from this conduit of stored information that the child can react, recall, and regret doing what he did in an informed way (these are the outputs).

However, when the child recalls his memory, which is stored in his soul, he will be pulling from information that was causally determined to be representative of the event; namely, photons of light hitting his retinas and sound waves penetrating his ear drums. The inputs into his soul and the outputs to his body would be causally generated and determined. Otherwise, if they boy’s memory and beliefs were not informed and determined by antecedent physical causes, then there would be no reason to think that his memory would be accurate to the event.

On what basis can one form beliefs, recall memories, or make informed decisions other than evidence?

So it seems the substance dualist is faced with a dilemma: either the inputs do not causally determine the subsequent beliefs formed in the soul and the outputs are not causally determined by those inputs, leaving the person completely detached from the world, or the soul is just a middleman in an otherwise completely deterministic process, leaving the substance dualist in no better position than the materialist or monist with respect to the problem of determinism.

End Notes

  1. Roderick Chisholm, from The Informed Philosopher, “Excerpt from Freedom and Action,”