Why Science Will Never Explain Consciousness

This post was co-authored with Ralph Weir, Senior Lecturer in Philosophy at the University of Lincoln. He is the author of The Mind-Body Problem and Metaphysics: An Argument from Consciousness to Mental Substance as well as academic articles on philosophy of mind, AI and human enhancement, metaphysics, and religion.

According to the standard model of physics, 61 elementary particles make up everything that exists: stars and planets, rocks and clocks, and even human beings. All of these objects are just different arrangements of the same basic particles.

In the case of human beings, though, something odd happens. Arrange the particles to form a rock or a clock, and all you get is a rock or a clock—an object with physical properties like shape, weight, and movement. But arrange the particles to form a human being, and you don’t just get an organism with a brain. You get one with a mind: a first-person perspective on the world, an internal space ablaze with colors, sounds, sensations, and emotions.

Philosophers call this internal world “phenomenal consciousness”—the inner qualities we experience when we enjoy the taste of coffee, watch sunlight glisten on a lake, or think about the Roman Empire. Scientists and philosophers have spent a lot of time and effort trying to figure out how an arrangement of unconscious particles could produce a conscious mind.

Phenomenal Consciousness versus Functional Consciousness

To see why this is such a conundrum, it’s important to realize that phenomenal consciousness is different from functional consciousness. The term “functional consciousness” refers to an organism’s ability to behave (that is, function) in certain ways—in particular, to respond appropriately to its environment or its own internal states.

It’s relatively easy to explain how an arrangement of particles could be functionally conscious. That’s because a “function” can be defined in wholly physical terms. It’s just about particles moving in particular ways in response to stimuli. It involves nothing more experiential than, say, an automatic door. For this reason, the term “functional consciousness” is a bit of a misnomer.

But, if a physical explanation of functional consciousness seems entirely possible, a physical explanation of phenomenal consciousness will be far more difficult. There is good reason to think it’s impossible.

Why would that be? Because it seems as though any physical system—any toing and froing of elementary particles—could go on perfectly well “in the dark,” without there being any conscious experience associated with it. After all, if an automatic door, a plant, or a computer can respond to its environment without experiencing anything, then why not a brain?

Theories About the Physical Correlates of Consciousness

Non-philosophers often assume that the task of explaining consciousness is just a really difficult brainteaser and that, after working on the problem long enough, it will finally become clear why certain arrangements of particles are conscious.

Specialists, however, know the matter is more complicated. To be sure, there are influential theories regarding the physical properties that correlate with consciousness. One theory identifies conscious processes as the ones that occur in a “global workspace” exchanging signals with regions throughout the brain. Another has it that consciousness occurs in systems that meet a mathematical measure of “integrated information.” Robert Lawrence Kuhn, the polymath creator of the PBS show Closer to Truth, has published an impressive survey of such theories (Kuhn, 2024).

However, theories about the physical correlates of consciousness do nothing to explain why these systems don’t just operate “in the dark.” The theories stop at the empirical observation that for some unknown reason certain physical systems and phenomenal consciousness go together.

Why a Physical Explanation of Consciousness Is Impossible

If we’re looking for physical science to explain phenomenal consciousness rather than just observe the physical properties with which it’s correlated, we’re necessarily going to be disappointed. And here’s why.

If we want to explain why water is a liquid at room temperature, we can say it’s because of the strength of the hydrogen bonds between H₂O molecules. The bonds are too weak to fix the molecules in place like in a solid, but strong enough to keep the molecules from spreading out as in a gas. This explanation works because there’s a conceptual connection between the weakness of the hydrogen bonds and the macroscopic properties of liquidity, such as the way a liquid takes the shape of its container.

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A physical explanation of phenomenal consciousness would require the same kind of conceptual connection between phenomenal consciousness and some physical activity. There would have to be some kind of particle movement that clearly could not happen without conscious experience. But no such conceptual connection exists.

That’s why, for example, a colorblind person can’t learn what it’s like to see color just by studying a textbook on the mechanisms of visual perception. And it’s why you can’t be certain from the physiology and behavior of other people whether colors look the same to them as to you.

There’s an essential logical link missing between the kinds of processes investigated by physical science and the conscious experience that sometimes accompanies them. And this makes a physical explanation of consciousness impossible.

Practical Implications

This conceptual impasse between physical processes and phenomenal consciousness has serious consequences. Researchers are being forced to explore surprising new avenues. These range from the theory that phenomenal consciousness is some kind of illusion to the theory that it is a fundamental part of reality in its own right, one that physics leaves out.

Our conclusions about consciousness bear on deep existential questions about human self-understanding. Should we think of ourselves as wet robots? Incarnate souls? Pieces of a fundamentally conscious universe, as advocated by the increasingly popular philosophy of panpsychism (Goff, 2019)?

As technology advances, the importance of understanding consciousness will grow. Could an AI become conscious, as former Google employee Blake Lemoine suggested? Might it be possible to radically extend human life by uploading our minds onto computers?

Recognizing the impossibility of explaining phenomenal consciousness in physical terms is the first step toward answering these questions.