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By Root 682 0

she comes into the room, you won’t know who she is; when she speaks, you will accuse the stranger before you of being an impostor imitating your mother’s voice. When she tells you her name and that she is your mother, it won’t help; you won’t recognize her. Otherwise, your responses to various stimulations will be perfectly normal. Once the neuroscientist turns off the magnetic field and thus reactivates the specialized neurons encoding the normal response to your mother’s face, you won’t have any trouble putting a name to it.

These neurons are just a clump of matter. They are not intrinsically about your mom. They don’t look like your mom. They are not like a picture of her. They can’t be interpreted or decoded by some other part of your brain into a picture or description of your mom. There is nothing that distinguishes them from any other reinforced synaptically connected neurons in your brain, except their history of being wired up as a result of early-childhood development and firing regularly under the same circumstances throughout your life.

None of these sets of circuits are about anything. And the combination of them can’t be either. The small sets of specialized input/output circuits that respond to your mom’s face, as well as the large set that responds to your mom, are no different from millions of other such sets in your brain, except in one way: they respond to a distinct electrical input with a distinct electrical output. That’s all packages of neural circuits do in the rat and the sea slug. That’s why they are not about anything. Piling up a lot of neural circuits that are not about anything at all can’t turn them into a thought about stuff out there in the world.

That was one lesson already learned by working through the Paris neurons: piling up more neurons, in the form of neural interpreters, for example, won’t turn any number of neurons already wired together into a circuit that is about anything else at all.

Go back to what’s going on in the sea slug neurons, whose molecular biology is just like our own neurons’ molecular biology. Sea slugs learn to do something when their neurons arrange themselves into a new input/output circuit. There’s no reason to suppose that once they learn to withdraw their siphons after they receive a mild shock, the sea slugs’ neurons start to constitute thoughts about mild electrical shocks or about siphon withdrawal or about anything at all. They have acquired some new circuit wiring, that’s all. There is no aboutness being produced in the sea slug neurons. When the rat acquires and stores information “about” the location of the life raft in the tank, that’s just the neurons in its hippocampus being reorganized into new input/output circuits. They have changed in the same way that the neurons in the sea slug have changed. Similarly, knowing what your mother looks like or that Paris is the capital of France is just having a set of neurons wired up into an input/output circuit.

The molecular biology of the sea slug conditioning, the rat hippocampus, and the human hippocampus are exactly the same—give or take a few amino acids and polynucleotides. When a human has learned something that introspection insists is a thought about something—like what your mother looks like—what’s really going on is something quite different. What’s really been “learned” is the exquisite coordination of so many packages of neural connections that the behavior it produces looks like it’s the result of thoughts about things in the world. That is especially how it looks to introspection. But looks are deceiving, as we so clearly saw in the last chapter.

Nevertheless, introspection is screaming at you that you do have thoughts about your mother. Scientism calmly insists that we will have to try to ignore this tantrum until the next chapter, when we have the tools to deal with it directly. Meanwhile, there is a third way of seeing that the brain can’t contain anything that is a thought about stuff. This way combines the first two reasons, the one from physics and the one from neuroscience.

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