Why your brain is not like a computer

Materialism is a branch of metaphysics which argues that everything that exists is ultimately physical. In this view, consciousness (your thoughts, sensations, and inner experiences) is emergent from the complex network of neurons that compose the brain. The most common way this idea is explained is through the brain-computer analogy: the brain is like a computer, neurons are like bits or transistors, neural firing patterns are computations, and conscious experiences are the outputs of those computations.

At first glance, this analogy seems compelling. Modern computers are made of nothing but physical components and yet they can display images, play music, and simulate entire virtual worlds. If these can "emerge" from a network of transistors on a screen, why can't our felt experiences also emerge from a network of neurons in the mind? The problem is that this analogy quietly assumes the very thing it is trying to explain.

Consider a triangle displayed on a computer screen. Physically, what's present are voltages in circuits and photons emitted from pixels at specific wavelengths. However, none of that is intrinsically a triangle. It only becomes a triangle because a conscious observer interprets those photons as one.

If no one were looking, nothing about the physical description would change, but the triangle would no longer exist as a triangle. There would be no shapes, no colors, no images; only electromagnetic radiation and electrical activity. In other words, the "emergent" property here is not a new physical object. It is a conscious experience.

This turns out to be true of nearly every standard example of emergence used to explain consciousness. Temperature is said to emerge from atomic motion, but experiences of "hot" and "cold" are not just atomic vibration, but ways things feel. Wetness emerges from collections of water molecules, but wetness itself is a tactile experience. In each case, what is supposedly explained depends on a conscious subject already being there. So using these examples to explain consciousness is circular. They don't show how experience emerges from matter; they rely on experience to make sense in the first place.

Now compare this to what happens when you close your eyes and imagine a triangle.

There is no screen. There are no photons. There is no external display and no separate observer interpreting a signal. And yet the triangle is immediately present. It has definite properties (three sides, color) even though it has no physical size, weight, or location in space.

Neuroscience can tell us a great deal about what is happening in the brain during this experience. We can identify correlated neural activity, track information flow, and even stimulate regions of the brain to reliably induce certain experiences. But correlation is not identity. Neurons firing are not the same thing as the triangle you experience, just as clapping hands is not the same thing as the sound that follows.^[1] Explaining every physical process involved still leaves a gap: why any of it is accompanied by experience at all.

A common objection points to people with aphantasia, who report an inability to form mental images. However, this does not remove the problem, but shifts it. People with aphantasia still report conscious experiences: inner speech, abstract thought, emotions, intentions, and a sense of understanding. The question simply changes from "Where is the triangle?" to "Where is the feeling of grasping an idea?" or "Where is the experience of deciding?" The puzzle is about subjective presence itself. Why is there anything it is like to think, feel, or understand, whether visually or not?

This is why the brain-computer analogy breaks down. It treats consciousness as if it were just another output of computation, when in fact consciousness is the very thing that makes outputs intelligible at all. You can explain every voltage, every spike train, and every algorithm, and still not explain why there is something it is like to be the system doing the explaining. That does not mean neuroscience is wrong. It means neuroscience describes the conditions under which consciousness appears, not consciousness itself. The triangle in your mind is real, but not in the way physical objects are real. It has properties, but not physical ones.

And that is at least a strong reason to think that consciousness is not just another thing the brain does, but something fundamentally different in kind.