Folks who believe in an immaterial soul (also known as ‘substance dualists’) face a daunting challenge. Why, if our mental and emotional functions are carried out by the immaterial soul, are they so completely affected by changes to the physical brain?

A common dualist response to this challenge is what I call the ‘brain as radio receiver’ model. In this model, the brain is something like a radio receiver, with the soul as the transmitter. The brain is constantly picking up signals from the soul and converting them into nervous impulses that are passed on to the rest of the brain and the body. When the brain is damaged or temporarily impaired, say by drinking, then the signals are no longer received clearly. The transmission isn’t affected, but the reception is.

This is a woefully inadequate model, for reasons that I’m sure we’ll discuss thoroughly in the comments. However, it’s understandable why someone who wants the soul to exist (particularly for religious reasons) would be attracted to it. What’s surprising is that David Eagleman, a neuroscientist who should know better, sees value in the model. At the end of his book Incognito, he writes the following:

As an example, I’ll mention what I’ll call the “radio theory” of brains. Imagine that you are a Kalahari Bushman and that you stumble upon a transistor radio in the sand. You might pick it up, twiddle the knobs, and suddenly, to your surprise, hear voices streaming out of this strange little box. If you’re curious and scientifically minded, you might try to understand what is going on. You might pry off the back cover to discover a little nest of wires. Now let’s say you begin a careful, scientific study of what causes the voices. You notice that each time you pull out the green wire, the voices stop. When you put the wire back on its contact, the voices begin again. The same goes for the red wire. Yanking out the black wire causes the voices to get garbled, and removing the yellow wire reduces the volume to a whisper. You step carefully through all the combinations, and you come to a clear conclusion: the voices depend entirely on the integrity of the circuitry. Change the circuitry and you damage the voices.

Proud of your new discoveries, you devote your life to developing a science of the way in which certain configurations of wires create the existence of magical voices. At some point, a young person asks you how some simple loops of electrical signals can engender music and conversations, and you admit that you don’t know — but you insist that your science is about to crack that problem at any moment.

Your conclusions are limited by the fact that you know absolutely nothing about radio waves and, more generally, electromagnetic radiation. The fact that there are structures in distant cities called radio towers — which send signals by perturbing invisible waves that travel at the speed of light — is so foreign to you that you could not even dream it up. You can’t taste radio waves, you can’t see them, you can’t smell them, and you don’t yet have any pressing reason to be creative enough to fantasize about them. And if you did dream of invisible radio waves that carry voices, who could you convince of your hypothesis? You have no technology to demonstrate the existence of the waves, and everyone justifiably points out that the onus is on you to convince them.

So you would become a radio materialist. You would conclude that somehow the right configuration of wires engenders classical music and intelligent conversation. You would not realize that you’re missing an enormous piece of the puzzle.

I’m not asserting that the brain is like a radio — that is, that we’re receptacles picking up signals from elsewhere, and that our neural circuitry needs to be in place to do so — but I am pointing out that it could be true. There is nothing in our current science that rules this out.

Eagleman is wrong about that. The ‘brain as radio receiver’ model isn’t scientifically viable. In the comments, let’s discuss all the reasons why. Any intrepid dualists who would like to defend the model are also welcome to participate, of course.