Which came first, the neuron or the feeling?

let's talk about consciousness again

In 1998, cognitive scientists Christof Koch and David Chalmers made a bet. Koch believed that within 25 years, we would have clear evidence about where in the brain consciousness resides—the “neural correlates of consciousness.” Chalmers believed consciousness is a much harder problem than that, such that we would still be far from a neuroscientific explanation of it after a quarter-century. In 2023, Chalmers won the bet.

The pair then renewed the bet for another 25 years: Koch believes that by 2048 we will actually have the neural correlates of consciousness pinned down. Chalmers still believes we won’t.

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In 1873, Camillo Golgi invented his eponymously named staining technique to create the first ever images of individual neurons. Neurons had been impossible to image until then because they were too densely entangled; Golgi’s method picks out a limited number of neurons at random to build a more comprehensible, albeit simplified, picture. A few years later Ramon y Cajal—widely described as the father of neuroscience—improved upon this method to create the first detailed wiring diagrams of small parts of the human brain. The two of them shared a Nobel prize in 1906.

An 1899 drawing of human neurons in the cerebellum, by Cajal (source).

In the hundred-plus years since, we’ve made enormous progress. Just a few months ago we mapped out the fruit fly connectome—the first map of every single neuron and synapse of the adult fly’s brain. That’s 139,255 neurons and 50 million connections.

A 3D rendering of all 139,255 neurons in the adult fruit fly brain (source).

But in one respect we are still woefully ignorant: we have no way of mapping from neurons to feelings. Sure, we have dozens of theories about consciousness (see this paper and this one)—but none of them have clearly won out over the others. As Donald Hoffman puts it, no theory of consciousness today can explain a single specific conscious experience, like the taste of mint or the smell of garlic.

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Maybe the search was flawed to begin with. You see, for most people contemplating this question, there is an overriding belief in materialism. We talk about the brain as generating our experience. Depression is a chemical imbalance and motivation is just dopamine. You could blame the Huberman stans for unthinkingly propagating this caricature of neuroscience, but it’s not really their fault. Even among thoughtful neuroscientists it’s taken for granted that experiential states are fully reducible to, and derivative of, physical processes in the brain. What else could they possibly be?

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Our widespread belief in materialism is an anomaly from a historical perspective. For most of history the standard view was idealism—the philosophical position that consciousness is primary. You could say that materialism began with Descartes’ attempt to separate the universe into res cogitans (mental stuff) and res extensa (physical stuff), a dichotomy he originally coined to separate the domain of religion (which cared about the mental) from the domain of science (which focused on the physical). In the centuries after Descartes, the success of science led many philosophers to conclude that the physical stuff is the fundamental substance of the universe, upstream of and causally dominant over the mental. For some philosophers, like the late Dan Dennett and the eliminative materialists, the physical stuff is all there is. Subjective experience is merely an illusion.

I’ve never been able to make much sense of the eliminative view—it seems to deny the existence of the very thing that is most obvious and present to us at all times. But then again, I have had the “obvious” fall out from under my feet many times before.

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Maybe it would help to reconsider our metaphors here. It’s clearly true that there is a tight coupling between physical brain states and subjective experience—ask anyone who’s just had a concussion or a dose of LSD—but it’s not as obvious which one is “causally dominant” over the other—which one comes first. Our brain states change our thoughts and feelings; but our thoughts and feelings also change our brain.

You could imagine that the brain is a projector and your experience is the contents projected on the screen. Or, you could say that the brain is a radio receiver and your conscious experience is the audio that’s read out. It’s not that the brain is creating the experience; it’s merely a receptacle for it. Or, you could flip the whole thing upside down: call your subjective experience the projector, and your brain is the contents projected on the screen. This isn’t as implausible as it sounds at first. Remember that the physical properties of the brain—that pink gooey squishy substance—is our own mind’s best attempt at drawing itself, at making sense of itself. On some level, the gooey squishy substance is just a construct of experience; the underlying reality is out of reach.

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There are lots of people taking seriously the possibility that consciousness could be primary, and building new theories of reality around it. Donald Hoffman claims that consciousness is fundamental to the universe—that underneath atoms and protons what we’ll ultimately find is extremely primitive conscious experiences which combine to give us the rest of physics. Bernardo Kastrup takes the same view but from the other side—the whole universe is one unified field of consciousness, which he calls “mind-at-large”, and this mind “dissociates” (think: multiple personality disorder) into individual minds which believe they’re distinct selves. Andres Gomez Emilsson talks about being a dual-aspect monist—he believes that consciousness and matter are basically two different angles on the same thing.

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Could atoms be conscious? It might sound absurd. But also, protons are the most complicated thing you could possibly imagine, so maybe they contain some absurdities. Also keep in mind that very concept of spacetime is doomed. Nothing should be taken for granted.

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Erik Hoel claims that consciousness is a Gödel sentence in the language of science. Godel was the one who came up with a number of incompleteness theorems—logical paradoxes that point to the hole at the bottom of math. Likewise, Hoel believes that consciousness could turn out to be the hole at the bottom of science—a fundamental barrier to science ever being “complete.”

Hoel writes:

Imagine a perfect map of an island. And I do mean perfect—even though it need not be as large as the island, it is exactly to scale, such that every rock, tree, and even grain of sand is represented on the map, in incredibly fine detail. Astounding, but still, at first, conceivable. Now imagine that the map is on the island itself. What happens? The observer is now in the observed. For if we think on that perfectly detailed map, we see that it must contain, within it, a map of the map. And that map must also be perfectly detailed, and contain a further map of the map. An infinite recursion. And what is a brain if not a map of the world? Like maps, brains represent the world around them, creating a world model. But the brain is a part of the world.

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Which came first, the neuron or the feeling? What was the universe like before there were any living beings around to observe it? Does it feel like anything to be a mushroom, or a bee, or a rock? What happens to your subjectivity when you die?

I’m not sure we’ll ever know. But I do know that life gets richer when you contemplate that either one of these—the neuron and the feeling—could be the true underlying reality. That your feelings might not just be the deterministic shadow of chemicals bouncing around in your brain like billiard balls. That perhaps all self-organizing entities could have a consciousness of their own. That the universe as a whole might not be as dark and cold and empty as it seems when we look at the night sky. That underneath that darkness might be the faintest glimmer of light. Of sentience. A glimmer of light which turns back on itself, in the form of you, asking the question of whether the neuron comes first or the feeling.