Our most human characteristic is also our least understood, and physicists remain divided on questions of mind and matter, writes science journalist Dan Falk.
Something remarkable happens inside our brains. Somehow, that gooey, three-pound lump of grey matter gives rise to a thinking, feeling mind.
From those billions of neurons and their assorted chemical and electrical interactions, consciousness emerges. And not just in humans; increasingly, scientists are acknowledging that some degree of consciousness is likely present in most mammal and bird species, and perhaps even in reptiles, amphibians, fishes, and many invertebrates such as mollusks and insects.
But how, exactly, do minds come about? The puzzle of consciousness is perhaps the most vexing in all of science.
Over the last few decades, neuroscientists have made great strides in identifying various brain states associated with specific mental states — like figuring out the neural underpinnings of vision, for example, or of language processing. Scientists who work on this are said to be studying the “neural correlates of consciousness.”
And while a tremendous amount of work remains to be done on this front, a much more difficult problem looms in the background – the question of how matter gives rise to minds in the first place (Why is it like something to be certain clumps of matter, and not like anything to be other clumps of matter?). The philosopher David Chalmers has dubbed this question the “hard problem” of consciousness.
The hard problem
Countless approaches to the puzzle of consciousness have been put forward over the years. Some 400 years ago, René Descartes argued that mind and matter are two distinct kinds of substances. But this dualist approach raises obvious problems — for starters, how might mind and matter interact? Claiming that they don’t interact is equally problematic — after all, what causes my hand to go up if not my conscious decision to raise it?
Alternatively, one might take a materialist or physicalist stance, and argue that the world we see around us is made up only of physical stuff; there is no “mind stuff.” Some scholars go further, making a leap from physicalism to illusionism, denying that consciousness exists in the first place. The argument goes something like this: Science can only concern itself with phenomena that are viewable “from the outside,” that is, from a third-person perspective.
But consciousness, as we usually imagine it, is inherently a first-person phenomenon. So whatever it is, it shouldn’t be treated as something objectively real, as something that scientists are obligated to try to explain.
Those who back illusionism appreciate how absurd the idea may seem at first glance. The philosopher Keith Frankish, one of illusionism’s most ardent proponents, writes:
“Most people find it incredible, even ludicrous, to suppose that phenomenal consciousness is illusory. But if the illusion has been hardwired into our psychology for good evolutionary reasons, then that is to be expected. The question is not whether illusionism is intuitively plausible, but whether it is rationally compelling.”
But illusionism doesn’t solve everything. Even if it seems to take the air out of the hard problem, it still leaves the question of how the illusion of consciousness comes about.
Not surprisingly, people like Chalmers see illusionism as wrong-headed; while we can be wrong about all sorts of things – the “lake” in the desert may be a mirage, and the stars that make up the Big Dipper have no actual dipper-like properties — we can hardly be wrong about our own consciousness, they would argue.
Indeed, some thinkers go further, arguing that it must be “consciousness all the way down.” This is the idea known as panpsychism, which posits that consciousness is a fundamental aspect of reality, something like mass or electrical charge.
The idea of mind as a fundamental constituent of the world goes back at least to the ancient Greeks, and has had many prominent supporters over the years, including the psychologist William James and the philosopher and mathematician Bertrand Russell.
Today that idea is seeing renewed interest, especially following the 2019 publication of Philip Goff’s Galileo’s Error, which argued forcefully that consciousness is fundamental to reality.
Panpsychism appears to provide a workaround to the question posed by Chalmers: we no longer have to wonder how matter gives rise to minds, because some degree of consciousness was there all along, residing in the fabric of the universe. Chalmers himself embraced a form of panpsychism in his 1996 book The Conscious Mind, even going so far as to suggest that individual particles may have some degree of consciousness. As he told a radio interviewer:
“The idea is not that photons are intelligent or thinking... it's not that a photon is wracked with angst because it's thinking, ‘Oh, I'm always buzzing around near the speed of light, I never get to slow down and smell the roses.’ No, not like that. But the thought is maybe photons might have some element of raw subjective feeling, some primitive precursor to consciousness.”
Neuroscientist Christof Koch has climbed on the panpsychism bandwagon as well, noting in his 2012 book Consciousness that if one accepts consciousness as a real phenomenon, and one that’s not dependent on any particular material — that it’s “substrate independent,” as philosophers put it — then “it is a simple step to conclude that the entire cosmos is infused with sentience.”
In the fall of 2023, I had the privilege of seeing the panpsychism debate unfold in real time when I attended a workshop at Maris College in Poughkeepsie, New York (and later wrote about it for Scientific American). At the meeting, some two dozen scholars debated the pros and cons of the theory. Presenters highlighted what they saw as physicalism’s shortcomings, while admitting that panpsychism has its own problems.
For starters, there’s the question of how small bits of consciousness come together to form more robust conscious entities. This is called the “combination problem,” which critics say amounts to panpsychism’s own version of the hard problem.
Others question panpsychism’s explanatory power. In his 2021 book Being You, neuroscientist Anil Seth wrote that accepting panpsychism “ushers the science of consciousness down an empirical dead end.” Others have been harsher. Science journalist John Horgan has called panpsychism “self-evidently foolish.”
A highlight of the meeting was a well-attended public debate between Goff and physicist Sean Carroll, a hard-core physicalist. In the debate, Goff pointed to physicalism’s failures; Carroll held up its successes.
Carroll is a supporter of what I call the “levels” argument: In the physical world, different phenomena manifest at different levels — and one has to be wary about mixing levels when one tries to explain things. An atomic-level explanation might be appropriate for a question in chemistry, for example, but it would likely be useless for tackling a question in economics.
Similarly, there is no such thing as “temperature” at the level of individual atoms, but with a conglomeration of billions of atoms, it’s a perfectly reasonable way of describing the amount of heat that’s present (Philosophers would say that temperature is an emergent property). Carroll admits that although it’s hard to explain consciousness at the microscopic level, it is nonetheless a real, emergent feature of the macroscopic world.
As the debate went on, Goff and Carroll turned to some of the famous thought experiments in the philosophy of mind, like the so-called “knowledge argument” (also known as “Mary in the black and white room”), as well as the “zombie” argument. Both arguments boil down to the same key question: Is there something about consciousness that cannot be accounted for by physical facts alone?
The zombie argument, for example, says that we can imagine a zombie-like creature that is physically identical to a conscious person, yet has no conscious experiences at all — suggesting that there’s something about consciousness that transcends physical reality. Opponents dispute that such an entity could exist; a creature that has those properties would necessarily be conscious, they would argue, just as a collection of H2O molecules in liquid form would automatically be water. Who won the debate? I encourage you to watch and decide for yourself:
While just about everyone agrees that the hard problem seems hard, many researchers — especially within the physicalist camp — believe it will eventually fade away. They draw an analogy with the debates that raged in the 19th century over the nature of life. What was it, people wondered, that made living things alive? Was there some kind of life force, an élan vital (as French philosophers called it)? Well, no. Instead, we came to recognize that “life” refers to a cluster of properties — metabolism, reproduction, homeostasis, and so on.
Anil Seth suspects that the puzzle of consciousness will one day “dissolve” in the same way. As he told me when I interviewed him recently for Quanta: “It’s going to be a case of saying consciousness is not this one big, scary mystery, for which we need to find a humdinger ‘eureka’ moment of a solution. Rather, being conscious, much like being alive, has many different properties that will express in different ways among different people, among different species, among different systems. And by accounting for each of these properties in terms of things happening in brains and bodies, the mystery of consciousness may dissolve too.”
My hunch (for what the hunch of a science journalist is worth) is that Seth is on the right track. Yes, consciousness is real and it’s emergent, just as temperature and many other qualities emerge when a system is complex enough.
It does us little good to label consciousness an illusion — but it is equally unhelpful to imagine that it permeates the cosmos like some invisible ether. Nor is there any reason to imagine consciousness to be so peculiar that it calls for a rethink of all of physics. (Physics is doing just fine — its “failure” to account for consciousness is no more disappointing than its “failure” to account for trickle-down economics, duck-billed platypuses, or any other emergent phenomenon. As Carroll put it in his 2016 book The Big Picture: “Consciousness isn’t an illusion — but it doesn’t point to any departure from the laws of physics as we currently understand them.”)
One day, perhaps quite soon, we will learn whether machines can be conscious, settling a question that has haunted debates over the nature of consciousness for the last 75 years or so.
Most physicalists would argue that there is nothing in principle that stands in the way. After all, we’re made of physical stuff, just as computers are; if we can be conscious, so can they. Interestingly, a panpsychist might very well reach the same conclusion — if everything is imbued with consciousness, then machines must be as well.
Perhaps the machines will one day tell us if they’re conscious, at which point it will be up to us to decide if we believe them. One might also wonder if they would believe us – a question dealt with humorously in a 1991 short story by American writer Terry Bisson called “They're Made Out of Meat.” In the story, two hyper-intelligent beings are crisscrossing the galaxy searching for life (What kind of beings they are is not specified, but it is implied that they are not biological). Eventually they stumble on what appear to be carbon-based life-forms “made up entirely of meat.” They ponder how such beings might exist, finally agreeing that such a thing is too bizarre to be believed, and mark our solar system as “unoccupied.”
And yet, here we are.
Dan Falk is a science journalist based in Toronto. His books include The Science of Shakespeare and In Search of Time. Follow him on X at @danfalk and on Instagram/Threads @danfalkscience.
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