Insight | Is consciousness fundamental? Physicists split on mind and matter

The Short Version

Four physicists give four answers to whether consciousness is fundamental. Thomas Campbell says yes, completely: consciousness is the base of reality, and the physical universe is a virtual reality it computes [1]. Adam Frank rejects that framing and also rejects its materialist opposite. He argues that science has a "blind spot": lived experience is the precondition for all science, yet science has written it out of its picture of the world [2]. Sean Carroll is a physicalist. For him, consciousness is as real as a table, but it is a way of talking about atoms and neurons, and he sees "no reason to change the laws of physics to account for it" [4]. Sara Walker is also a physicalist, but she says our idea of matter is incomplete. She resists treating consciousness as fundamental and suggests it comes from being an object stretched deep in time [3]. The positions range from mind-first to matter-first, with Frank's experience-first view cutting across both. Laying them side by side shows where the real disagreements are: what "fundamental" means, what role information plays, and whether a third-person view of reality is even possible.

What They Said

Thomas Campbell: consciousness first, the universe as a computed virtual reality

Campbell trained in low-energy experimental nuclear physics and is the author of the My Big TOE trilogy [1]. His path to his position started with experiences his materialist training couldn't explain. As a PhD student in the late 1960s, he learned meditation. One day, while thinking about a failed computer job, he saw his code scroll through his mind with the faulty punch cards highlighted in red. When he checked the actual cards, they had errors, including tiny mechanical misalignments nearly impossible to see. "It was always accurate," he says, and the experience hit his worldview like a sledgehammer [1]. In his words: "here I was, right in my face, there's another part to reality that consciousness centered" [1]. He then spent 15 to 20 hours a week at Robert Monroe's out-of-body research lab, and says 35 years of repeated experiments convinced him that causality runs from consciousness to the physical [1].

His model is plain: "we live in a virtual reality. This physical reality is computed. Now, it's been computed by consciousness" [1]. Individual consciousness is part of a larger system: "there's a system of consciousness. And we're just a piece of that system." The body is an avatar, not the self: "you are not a human. That's an avatar. You are a piece of consciousness" [1]. He compares it to World of Warcraft. The game's world "actually doesn't exist. It's just computer-generated eye candy for the players," yet from inside the game everything feels physical [1]. In the same way, "The overall thing is consciousness and it's sending you and I a data stream," which we interpret as rivers, houses and people [1].

Campbell defines consciousness simply: "It's an awareness with a choice" [1]. He builds the system up from nothing. It starts as a binary unit that can choose between states and make patterns, then patterns of patterns. It invents time by oscillating like a metronome, then splits off pieces of itself with free will, which he likens to virtual machines on a mainframe [1]. Its purpose is to evolve by lowering its entropy, which in human terms means becoming more loving and cooperative [1]. Our universe, he says, was built from initial conditions plus a rule set, run many times with the constants adjusted until it produced avatars capable of meaningful choices. That is his explanation of the anthropic principle, the observation that physical constants seem finely tuned for life [1]. He says the model rests on a single assumption, that consciousness exists [1].

The model makes strong claims about the brain. "There's no information stored in your brain. Your brain doesn't do any computations, doesn't process anything. All that's done in consciousness" [1]. It goes further: "You only render the stuff that other people can sense," so "neither one of us have a brain being rendered unless somebody cracks open our skull" [1]. A brain injury, on this view, doesn't damage consciousness. It changes what the player can do through the avatar [1]. He also offers explanations for physics. The speed of light is constant because space and time have smallest units (the Planck length and Planck time), so the top speed is one pixel per tick [1]. Entanglement, the "spooky action" linking distant particles, is simply "an if-then statement. This is code" [1]. Measurements are random draws from a probability distribution, and only what is observed gets rendered [1].

Joe Rogan pushes back: if we can send a rover to Mars and measure things, what makes reality virtual? Campbell's answer: "it's virtual because it's computed. It's a computed reality" [1]. Borrowing from physicist Edward Fredkin, he says the computer running it can't be inside the reality it computes: "virtual reality doesn't compute itself" [1]. He adds a comparison to dreams: "When you dream, that's a virtual reality," and it is "no more or less real than this reality." Ours looks physical only because it has "a tight rule set that defines every energetic exchange" [1].

Campbell's standard of evidence is personal: "if it's not your experience, then it can't be your truth" [1]. When Rogan asks why he doesn't record and publicize demonstrations, Campbell says "demonstration convinces nobody except the people who were there," which Rogan calls "a cynical perspective" [1]. Campbell's answer is his nonprofit, the Center for the Unification of Science and Consciousness (CUSAC). It is running quantum physics experiments proposed in a paper he published in a peer-reviewed journal, one of which he says is finished, along with video-game experiments testing whether players' intention can shift random outcomes [1]. On AI, he says there is no test for consciousness. In his model, an AI becomes conscious the same way a human does: a piece of consciousness logs on and plays it as an avatar once its choices matter [1].

Adam Frank: the blind spot is experience itself

Frank, an astrophysicist, wrote The Blind Spot with Marcelo Gleiser and Evan Thompson [2]. He deliberately doesn't take either side of the old debate. His target is a hidden set of assumptions: "It's a metaphysics that got glued on science." The blind spot, he says, is "experience, it is presence," the raw lived world that phenomenology calls the life world, "this sort of raw presence that you can't get away from until you die" [2]. The book's central claim is that "that is the precondition for the possibility of science" [2]. Science "purposely pushed that out, it pushed that out so it could make progress," which works for certain problems. But when we go deeper, into "the nature of consciousness, the nature of time, quantum mechanics," it "comes back to bite us," leaving paradoxes that require "this intellectual yoga" to escape [2].

He explains this with what he calls the parable of temperature. We now treat degrees Celsius as simply out there: "the molecular cloud in space is 10 degrees Kelvin." But science began with "the subjective experience of hot and cold." Thermometers extracted what philosopher Michel Bitbol calls structural invariants, the parts of that experience everyone could agree on, and from them science built thermodynamics [2]. Then it forgot where it started and began treating 60 degrees as more real than the feeling of being cold, an "amnesia of experience" [2]. In his words: "Part of the blind spot is substituting a formal system, a calculus of data for actual experience" [2].

The blind spot is a constellation, it's not just materialism. It includes reductionism ("you are nothing but your nerve cells, which are nothing but the chemistry, which is nothing but all the way down to quarks"), the God's-eye objective view, physicalism, and "the reification of mathematics, that mathematics is somehow more real than this" [2]. Together, "they end up pushing experience out and saying experience is an epiphenomena" (a mere side effect) [2].

Frank is careful about his words. "I tend not to use the word consciousness because it's, I think it leads us in the wrong direction. We should focus on experience," because experience is "verb like [2]. For him, experience is not a thing you have, it is a thing you do [2]. He also doubts the brain is the whole story: the brain is not the minimal, the minimal structure for consciousness, you know, like it's the whole body, it's embodied," and even "it's communities actually [2]. He favors the 4E" view of cognition: embodied, embedded, enacted and extended [2]. He illustrates it with a story. Gregory Bateson asked Jonas Salk where his mind was; Salk pointed to his head, and Bateson said no, out here [2].

When Lex Fridman suggests Frank might be saying experience sits "at the core of reality," Frank declines: "Yeah, but I wouldn't do it," pointing to panpsychism as the move he's avoiding [2]. He rejects both schools: "Physicalism says, all that exists is physical. Idealism says all that exists is mind." Taking either position, he argues, "is already to project out into that third person view," and that view "is a fiction. It's a useful fiction when you're doing science." For billiard balls on a pool table, fine. But for deeper questions, "I can't ignore the fact that there really is no third person view" [2]. Following Alfred North Whitehead, he wants to avoid "the bifurcation of nature," the split between scientific concepts on one side and lived qualities on the other [2].

He sees quantum mechanics pointing the same way. Its measurement rule (the Born rule) says measurements matter. The many-worlds interpretation avoids this by inventing infinite unobservable universes, while QBism (quantum Bayesianism), developed by Chris Fuchs and colleagues, puts the agent and information at the center [2]. On time, he recounts philosopher Henri Bergson's challenge to Einstein: relativity's block universe is a powerful map, but lived time, like hearing music, has a different structure. His summary advice: "don't confuse the map for the terrain" [2].

Frank argues the blind spot has real costs outside science. Science tells us we're insignificant machines, while cosmology and quantum mechanics put observers at the center, and the result is a crisis of meaning. People respond with scientific triumphalism, science rejection and pseudoscience [2]. He was surprised that Science, Nature Physics and the Wall Street Journal all reviewed the book positively, and reads that as a sign of "some dissatisfaction with this triumphalist view" among working scientists, who feel "stuck in a vortex" [2]. Meanwhile, experience fundamentally is weird, you know, mysterious... There is always more [2].

Sean Carroll: physicalist, but consciousness is real

Carroll, a theoretical physicist at Johns Hopkins, sets out the case he opposes clearly before rejecting it. Panpsychism, the idea that consciousness pervades all matter, is supported by Philip Goff, whom Carroll credits with being "almost single-handedly responsible for the upsurge of interest in panpsychism," and entertained by David Chalmers, who is "panpsychism curious" [4]. The argument is "that there is something fundamentally uncapturable about conscious awareness by physical behavior of atoms and molecules." Neuroscience might one day tell me which neurons fire, "What you can't tell me is what it is like to be me" [4]. From there, the panpsychist says, "I need something that is not contained within physics to account for that. And I'm just going to call it mind" [4]. That leaves two options. You can be a dualist, with mind and matter interacting somehow, which Carroll calls "a little bit complicated and sketchy as far as physics is going to go." Or you can say "that mind comes first and that consciousness is the fundamental aspect of reality and everything else, including matter and physics comes from it" [4]. That second option is essentially Campbell's view.

Carroll's reply: "the physicalist, such as myself, will say, I don't have any problem explaining what is like to be you or what you experience when you see red. It's a certain way of talking about the atoms and the neurons" [4]. His comparison is furniture: "Just like the hardness or the brownness of this table, these are words that we attach to certain underlying configurations of ordinary physical matter" [4]. He's modest about the details: "I do not claim to have any special insight on how consciousness works other than I see no reason to change the laws of physics to account for it" [4].

He refuses to call consciousness an illusion. "I almost never use the word illusion. Illusion means that there's something that you think you're perceiving that is actually not there" [4]. Consciousness and free will are as real as tables and chairs [4]. His philosophy, which he calls poetic naturalism, holds that only the natural world exists but that there are many valid ways to talk about it. "Even though you know that it's really a quantum field theory wave function, right, tables are still real" [4]. On mind and reality, he says "we're part of the physical world and the natural world" [4].

Carroll is also skeptical of the simulation idea behind Campbell's model. He sees no philosophical knockout argument against it, but says "there's absolutely no reason to take it seriously" [4]. He adds a practical point: "people will realize how much harder it is to simulate a realistic world than we naively believe" [4]. Interestingly, he cites David Chalmers' argument "that we should treat things that happen in virtual reality and in simulated realities as just as real as the reality that we experience" [4]. That echoes Campbell's claim that a computed world is still fully real from the inside [1].

On quantum mechanics, Carroll takes the opposite side from Frank. He defends many worlds: the Schrödinger equation says the observer becomes entangled with what is measured, so nothing collapses, and you simply find yourself in one branch [4]. He admits it requires new philosophy about identity and probability, but thinks cautious physicists are "wimping out" [4]. Where he looks for what's next is complexity. He thinks the key is information: subsystems of the universe learning to use information to survive and thrive [4]. Life doesn't fight the second law of thermodynamics: "We are surfers riding the wave of increasing entropy," sustaining ourselves by burning low-entropy fuel [4]. With a student he is sketching what he calls "complexogenesis," a sequence running from configurational complexity, to stars burning fuel, to life using information, to minds that imagine futures [4].

Sara Walker: physicalist, with an incomplete idea of matter

Walker, an astrobiologist and theoretical physicist, opens by reframing the old split between vitalists and materialists [3]. Vitalists think something beyond material properties animates living things; materialists think there is nothing special about the matter life is made of [3]. She says the universe is a giant mystery, but not magic, just the unknown, and that no long-lived tradition, vitalism included, is ever fully wrong [3]. Her key move is that our concept of matter is itself an invention, tied to the technologies of an era. Aristotle explained motion with earth-like, air-like and celestial properties until instruments that measured time and tracked the planets let mass and acceleration unify everything [3]. The problem with life, she says, is that we don't yet know how to think about information in a material way. If we did, we might find life is a material property that still has many of the features vitalists found mysterious [3].

Her definition of life comes from that view: "life is the process of how information structures matter over time and space" [3]. Living objects are huge in time: "The universe is far larger in time than it is in space" [3]. From this she offers a tentative account of consciousness. She resists assuming consciousness is fundamental or that it existed before life. We have conscious experience, she suggests, because we are temporally extended objects with a huge inner space. It is private because no one else occupies the same thread of time, and shared ancestry lets us partly share experience through language [3]. She describes intelligence as the ability of objects with a lot of selection embedded in them to select possible futures [3].

Walker also rejects the claim at the center of Campbell's model, that reality is a computation. Her view is that the world is not a computation, but computation is our best current language for understanding it [3]. Computation sits at the top of reality, not the base: our biosphere built it after billions of years of evolution, and it only happens in some physical objects [3]. She tells of a conversation with John Conway. String lights in a barn can be programmed as a cellular automaton capable of universal computation, but that property belongs to the programmer's theory, not to the lights [3]. When Stephen Wolfram argued that computation is fundamental, she replied that computation is simply his turtle, the thing he assumes everything else stands on. Everyone needs a turtle, she says, but it should follow from the question you are asking [3].

She is also skeptical that reality has a final ground. She doesn't believe in a theory of everything, quoting David Krakauer: "a theory of everything is a theory of everything except those things that theorize" [3]. What we call fundamental particles are really the limits of what our instruments can resolve. Atoms were once "indivisible" until better instruments showed their parts [3]. She flips the usual order: the truly fundamental things are constructed objects whose histories we can understand by taking them apart [3]. Like Frank, she isn't a many-worlds person. In her view, all those branches are bundled into the deterministic, macroscopic object that is you, carved out of a random quantum background [3]. She calls herself an avowed physicalist: nothing exists outside the universe, and even mathematics and the multiverse exist here, in human minds and the biosphere [3]. On AI consciousness, she says we need a testable theory of consciousness before the question can leave the gray area [3].

Where They Agree, and Where They Don't

The spectrum. Campbell is fully mind-first: consciousness is the only assumption, and matter is rendered [1]. Carroll is matter-first: consciousness is a real, higher-level way of describing physical processes, and physics needs no changes [4]. Walker is matter-first too, but insists we don't yet understand matter, especially how information lives in it [3]. Frank refuses the axis altogether, because both ends assume a third-person view he calls a fiction [2].

Is there a view from nowhere? This is the sharpest split. Carroll's physicalism depends on the idea that redness is "a certain way of talking about the atoms and the neurons," a description from outside [4]. Frank says "there really is no third person view" when you ask deep questions [2]. Campbell also denies a neutral outside view, but he replaces it with a larger consciousness system that computes everything, the very kind of God's-eye frame Frank would call projecting outward [1][2].

Illusion or not. Oddly, all four resist calling experience an illusion. Carroll says consciousness is as real as a table [4]. Frank makes experience the precondition of science [2]. Walker grounds it in temporal depth [3]. Campbell says dreams and waking life are equally real [1]. They disagree about what experience is, not whether it's real.

Computation. Campbell's universe is literally computed by consciousness, and "virtual reality doesn't compute itself" [1]. Walker says computation was built by life late in the story and can't be the base [3]. Carroll says the simulation hypothesis has "absolutely no reason" to be taken seriously [4]. Frank favors embodied, extended cognition over the idea of uploading minds into computers [2].

Entropy and information. Campbell and Carroll both put information and entropy at the center, but in opposite directions. For Campbell, consciousness evolves by lowering its entropy [1]. For Carroll, life rides rising entropy, using information to survive [4]. Walker says the hope that non-equilibrium physics and entropy will explain life is the wrong approach; the real question is how life generates so much order from randomness [3].

Quantum mechanics. Campbell reads measurement as random draws rendered on observation [1]. Frank prefers QBism, which puts the agent at the center, and criticizes many worlds [2]. Carroll defends many worlds and calls the cautious "wimping out" [4]. Walker rejects many worlds [3].

Evidence. Campbell relies on personal experience and his own experiments, and doubts that demonstrations persuade anyone [1]. Carroll's test is whether the laws of physics need to change, and he sees no sign they do [4]. Walker wants a testable theory of consciousness before any verdict [3]. Frank argues that the standards themselves were built on the experience they leave out [2].

Why It Works

The sources explain why the question is so stubborn.

The argument from what it is like. Carroll sets out why people are drawn to mind-first views. A complete neural account still seems to leave out "what it is like to be me," which pushes some toward a separate mind [4]. His answer is that "what it is like" is a higher-level description, like hardness [4].

The history of abstraction. Frank's temperature parable explains why the question feels unanswerable. Science reached precision by stripping experience out, so experience can't be found back inside its equations [2]. The paradoxes around consciousness, time and quantum mechanics are the price [2].

Moving the boundary. Walker shows that "fundamental" moves as instruments improve. Atoms were "indivisible" until they weren't, and motion was mysterious until the right measurements existed [3]. If information in matter becomes measurable, the mind-matter question may be reframed the same way [3].

Consistency with physics. Carroll's case rests on parsimony: where physics already works, adding mind as a new ingredient costs more than it explains [4]. Campbell turns that argument around. He claims one assumption, consciousness, explains more: the speed of light, entanglement, fine-tuning, and paranormal experience [1]. Which view is simpler depends on what you think needs explaining.

Where It Applies, and Where It Doesn't

• For everyday physics, every side agrees the third-person approach works. Frank accepts it for billiard balls [2], and Carroll's tables are real at every level [4].
• For consciousness, time and quantum measurement, Frank thinks the approach breaks down [2], while Carroll thinks its current tools suffice [4].
• For AI, the views give different tests. Campbell says a piece of consciousness logs on once choices matter [1]. Walker says we need a testable theory first [3]. Frank doubts current language models have agency, given his embodied view [2]. Carroll is a physicalist who sees no obstacle in principle to thinking machines, but warns that we project intentions onto anything humanlike [4].
• Campbell's claims about the paranormal (remote viewing, out-of-body travel, a brain that does no computation) go well beyond what the other three accept. He says his evidence is largely first-person, and his larger experiments are still under way [1]. Readers should treat them as his proposals, not settled findings.
• Walker's account of consciousness is explicitly tentative [3], and Carroll says plainly he has no special insight into how consciousness works [4]. Nobody here claims to have solved it.

What To Do With It

1. Pin down which "fundamental" is meant. Campbell means that consciousness computes matter [1]. Frank means experience is the precondition of any science [2]. Keep these separate.
2. Try Frank's temperature exercise. Take a scientific quantity like temperature and trace it back to the felt experience it was abstracted from, to see what the number leaves out [2].
3. Test the "illusion" word. Following Carroll, ask whether the thing you'd call an illusion is actually absent, or just described at a different level [4].
4. Ask whether a proposal changes physics. Carroll's filter is useful: if a theory of mind requires new laws, it needs evidence to match [4].
5. Treat computation as a language, not a verdict. Following Walker, ask whether a claim that "reality is computed" is about the world or about the theory describing it [3].
6. Watch for the third-person move. When any theory, materialist or idealist, describes reality from outside, notice that Frank calls that stance a useful fiction [2].
7. Weigh Campbell's experiments on their results. He points to CUSAC's quantum and intention experiments as the evidence to come [1]. Judge the model by what they show.
8. Hold out for a testable theory of consciousness. On AI and beyond, Walker's standard is that claims stay in the gray area until one exists [3].

Sources

1. Thomas Campbell · The Joe Rogan Experience
2. Alien Civilizations and the Search for Extraterrestrial Life · Lex Fridman Podcast
3. Sara Walker: Physics of Life, Time, Complexity, and Aliens · Lex Fridman Podcast
4. Sean Carroll: General Relativity, Quantum Mechanics, Black Holes & Aliens · Lex Fridman Podcast