Part of the extended series Evidence for the Faith
Ah, the interaction problem finally appears on the stage. I was expecting it to arise in the course of my discussions about humanness and evidence for the faith. I had decided not to include it until someone brought it up. The question is: if the physical brain is not the whole story, and if human mind is immaterial, how does that immaterial mind interact with the physical world?
Not Ruled Out By Science
1. There is increasing evidence that the brain acts as a quantum effects amplifier. Mind could influence the physical world at the quantum level without violating conservation of energy, Daniel Dennett has identified as the chief scientific objection to immaterial mind. I don’t know if that’s how mind interacts with the brain, but as long as it remains a possibility, science doesn’t rule out an immaterial mind.
Proving Too Much With the Interaction Problem
2. To make this the deal-killer for human immaterial minds is also, probably, to make it a deal-killer for theism, for theism posits God as immaterial mind who interacts with the physical world.
More specifically, if non-theists say the immaterial cannot affect the physical, they are in effect saying that God doesn’t exist or does not interact with his own creation, which by the way he probably couldn’t have created, either.
That should give the skeptic pause. If God could be disproven that easily, someone would have built that case a long time ago. There’s a reason that hasn’t been done, at least not very prominently: it begs the question of God. It practically asserts God out of existence: “There is no God, or there is no God who interacts with the physical world, because the immaterial cannot interact with the material.” The theistic answer to that is quick and easy. “Really? How did you come to know that much about what God could or couldn’t do, if there is a God?”
But suppose the non-theist were to say this:
This isn’t about God, it’s about humans. God is posited as wholly other, wholly transcendent, totally omnipotent. I won’t try to include him in this argument because I can’t pretend to understand what he could or couldn’t do, if he existed. Humans, on the other hand, are familiar territory. We’re in the physical world. To posit an immaterial soul that can interact with the physical world is to suggest that humans have a God-like supernatural ability to touch the physical world from an immaterial place.
My answer would be, Sure! Why not? The biblical account is clear: God created humans in his image. Like God, and unlike the animals, we are rational creatures with moral and spiritual dimensions. Why not also have an immaterial dimension with some limited ability to affect the physical world? To deny that possibility is, again, to assert the biblical view of humanity out of existence. It’s just as question-begging as the question above, concerning God himself.
The Evidence from Neuroscience
3. The non-theist will probably point to neuroscience as evidence that cognition and behavior depend on the brain, and of course we would agree. We only disagree on whether demonstrates that it is dependent on the brain alone, and nothing but the brain.
Look at it this way. I have a long-term foot injury. I’m recovering from tendon transplant surgery almost nine weeks ago, and I still cannot walk more than a few steps at a time. I have a problem expressing my will in the physical world. I’d like to walk to the next room and refill my coffee mug, but I can’t do it without an assistive mobility device (or at least, not without more pain than I care to experience).
Everyone knows that between the will and the act there is a physical interface, and that this interface can malfunction. I have a malfunction in my foot, with an obvious effect in the physical world. I could also have a malfunction in the part of my brain that controls that foot, which could likewise have an effect in the physical world. A brain issue would be upstream of an ankle tendon issue, but it would be in the same stream. A glitch in the physical stream can have a physical result. That’s not news to any theist.
It’s also well known that neural stimulation can produce behavioral effects. E-stim (electrical current through the foot) in the physical therapist’s office can make your toes curl. A high enough voltage with a pathway to ground can make you hold on to a wire and be unable to let go. Similarly, as Willard Penfield discovered some fifty years ago, electrical stimulation in the brain can produce behaviors and cognitions. Interestingly enough, though, patients always knew it wasn’t them doing it; they knew it was being done to them. Penfield decided this was best explained on the theory that the brain isn’t the sole seat of identity and behavior.
Explaining the Interaction
4. Finally, the non-theist will likely say, You can claim this interaction is real, but you could never show how it happens, so it’s no explanation at all. The theistic response (and now I’m speaking specifically of substance dualists; see below) is to ask what one means by explanation. Typically in today’s mindset, explanation means a description of how things interact physically: the conditions and causes that bring out a result according to physical laws. Applied in this context, the request becomes: Show us the physical manner in which non-physical mind touches the physical world; which is near neighbor to, Show us that non-physical mind is really physical after all.
It’s a question-begging request, in other words. It assumes that the working of that which is non-physical must be describable in physical terms, which is to say it assumes that the non-physical isn’t non-physical after all.
Admittedly that leaves the substance dualist still without an explanation for how immaterial mind interfaces with the material world. I’m okay with that. We don’t have mental categories for that kind of explanation, any more than we have categories to explain how nature’s physical laws came to be. Call it a mystery, call it a matter for continued research, call it what you will: the question is not whether we can or cannot explain the workings of this interface, the question is whether there’s evidence that it’s real.
The Hylemorphic Dualist Position
Some of this blog’s frequent commenters opt for hylemorphic dualism, which posits an immaterial soul, but not as a discrete immaterial substance. As I have already said in this series, I’m not fully settled on what I believe: I lean toward substance dualism but I could see myself being persuaded otherwise.
One advantage of hylemorphic dualism is that there is no interaction problem in it. Therefore if I’m wrong at this stage, and if hylemorphic dualism is a better description of human reality than substance dualism, I have at least defended the more potentially problematic position. A successful defense of interaction under substance dualism would mean that there is no real interaction problem under any prominent Christian position. If my points 1 through 4 are successful, then the skeptic’s challenge has been met, one way or the other.