David Chalmers

• 1. Introduction

  ›

  David Chalmers was born in Sydney on the 20th of April 1966, and from a young age he seemed wired differently. At 10, he was writing code and playing computer games on a PDP-10 at a medical center. At 13, he picked up Douglas Hofstadter's 1979 book Godel, Escher, Bach, and something clicked. He won a bronze medal at the International Mathematical Olympiad. He also experienced synesthesia, a condition where senses blend into each other, hearing colors or seeing sounds.

  The question his life would come to orbit was not about mathematics or code, though. It was far older and stranger: why does experience exist at all? When you see red, you do not just process light at a certain wavelength. Something happens. There is something it feels like. Why? That question, which Chalmers would eventually name the hard problem of consciousness, has no easy answer. Physicists can tell you how the eye works. Neuroscientists can map the visual cortex. But none of that explains why there is any experience happening at all.

  Chalmers became the philosopher who put that question on the map of serious science, doing so at a lecture in 1994 that one publication described as having goosed a nascent field into greater prominence. He would go on to hold chairs at UC Santa Cruz, the University of Arizona, the Australian National University, and eventually New York University, where he now serves as professor of philosophy and neural science. How a mathematician-turned-hitchhiker became one of the most cited philosophers alive is itself a remarkable thread.

• 2. The Road to Philosophy

  ›

  Unley High School in Adelaide, South Australia, is where Chalmers attended secondary school, and by that stage he had already shown he was not an ordinary student. Mathematics came naturally enough to earn him recognition at the International Mathematical Olympiad. But it was a book, not a theorem, that redirected him.

  Hofstadter's Godel, Escher, Bach sat at the intersection of logic, music, art, and mind. Reading it at 13 planted a question Chalmers could not shake: what is the relationship between computation and consciousness? He pursued mathematics through to a pure mathematics degree at the University of Adelaide. Then, rather than heading straight to graduate school, he spent six months hitchhiking across Europe, reading philosophy books along the way. He was accepted to the University of Oxford as a Rhodes Scholar but eventually withdrew from the course.

  He found his way to Indiana University Bloomington, where the same Hofstadter who had sparked his curiosity at age 13 was now his doctoral supervisor. In 1993, Chalmers received his PhD in philosophy and cognitive science, with a thesis titled Toward a Theory of Consciousness. The following two years he spent as a postdoctoral fellow in the Philosophy-Neuroscience-Psychology program directed by Andy Clark at Washington University in St. Louis. Clark would later become a close collaborator on questions about the mind that reach well beyond the skull.

• 3. The Hard Problem

  ›

  In 1994, at the inaugural Toward a Science of Consciousness conference, Chalmers delivered a lecture that the Chronicle of Higher Education later said established him as a thinker to be reckoned with. He named a distinction that researchers had circled around without quite pinning down.

  The easy problems of consciousness, as Chalmers framed them, are things like explaining how the brain discriminates between objects or produces verbal reports about what it perceives. These are hard in the scientific sense, meaning they may take decades to solve. But they are tractable. Physicalism, the view that everything is ultimately physical, provides at least a theoretical path forward: map the mechanism, and you explain the function.

  The hard problem is different. It asks why any of that processing is accompanied by subjective experience. Why does awareness feel like anything at all? Chalmers argues there is an explanatory gap between the objective description of brain states and the subjective reality of experience, and that gap cannot be closed by more neuroscience alone. His 1995 paper Facing Up to the Problem of Consciousness and his 1996 book The Conscious Mind laid out this argument in full. After the paper appeared, more than twenty responses were published in the Journal of Consciousness Studies, from philosophers and scientists including Daniel Dennett, Colin McGinn, Francis Crick, Roger Penrose, and Francisco Varela. That collection was later published as the book Explaining Consciousness: The Hard Problem. John Searle offered his critique in The New York Review of Books.

• 4. Zombies and Qualia

  ›

  Philosophical zombies are not the undead of horror films. In Chalmers's thought experiment, a zombie is a being physically identical to a human in every respect, atom for atom, yet with no inner experience whatsoever. No feelings, no sensations, no subjective life. Lights on, nobody home.

  Chalmers argues that such creatures are conceivable. And if they are conceivable, then they are logically possible. If they are logically possible, then consciousness cannot be fully explained by physical properties alone. The facts about experience are, in this view, further facts, not reducible to any facts about neurons or computation. Chalmers traces a version of this line of thought back to Leibniz's 1714 mill argument; the first substantial use of philosophical zombie terminology, he notes, may be Robert Kirk's 1974 paper Zombies vs. Materialists.

  He calls his own position naturalistic dualism. He accepts that mental states depend naturally on physical systems like the brain. He denies that they are ontologically identical to them. He also entertains a further, more startling extension: if consciousness is a fundamental property, it might attach to any information-bearing system. This leads him toward what he calls panprotopsychism, a qualified version of panpsychism. He maintains formal agnosticism on the question but acknowledges it puts him at odds with most of his colleagues.

  Two thought experiments sharpen the picture. The fading qualia experiment, proposed in 1995, imagines replacing each neuron with a functional silicon equivalent, one by one. Because each replacement performs the same function, the subject notices no change. But if qualia were to fade with each swap, the brain's holder would notice, which would alter information processing and generate a contradiction. Chalmers concludes that fading qualia are impossible, and that a brain rebuilt neuron by neuron in silicon would be as conscious as the original. The dancing qualia variant extends this: such a brain would not just be conscious, but would have the same conscious experiences.

• 5. Language and Meaning

  ›

  Before Saul Kripke delivered his lecture series Naming and Necessity in 1970, the field of reference theory was dominated by descriptivism. As advocated by Gottlob Frege and Bertrand Russell, this view held that names are shorthand for descriptions, and that whichever object best fits a given set of properties is what the name refers to.

  Kripke dismantled that picture. Names, he argued, trace their reference through historical-causal chains, not descriptions. The name "water" refers to H2O not because H2O fits some description of water-like properties, but because there is a continuous chain linking back to the original act of naming. On Kripke's account, a name is a rigid designator: it picks out the same object across all possible worlds. Hilary Putnam extended a similar argument to natural kind terms.

  Chalmers disagrees, and with collaborators including Frank Jackson he developed a framework called two-dimensional semantics. His central move is to say that a word like "water" carries two distinct kinds of meaning, a primary intension and a secondary intension. The primary intension is the method by which we identify the referent, something like the substance with water-like properties. The secondary intension is what the word actually picks out in this world, namely H2O. In a twin Earth thought experiment, inhabitants might use the word water to describe a chemically different substance with the same surface properties. On the primary intension, their word refers to that substance, not H2O. On the secondary intension, water is still H2O across all possible worlds.

  This framework matters because it attempts to reconcile how reference can feel conceptually open while being metaphysically fixed, distinguishing between what is epistemically possible and what is metaphysically necessary.

• 6. Virtual Worlds and AI

  ›

  Chalmers's 2022 book Reality+ takes the philosophy of mind into territory that might seem speculative but follows directly from his core arguments. If consciousness depends on functional organization rather than biological substrate, then a virtual world could support genuine experience. Chalmers does not treat virtual reality as an illusion; he treats it as a genuine reality in its own right, potentially as meaningful as any non-virtual life.

  He also proposes that computers are forming what he calls an exo-cortex, a kind of extended cognitive organ, where portions of human thought are effectively outsourced to companies such as Apple and Google. This idea connects to the extended mind thesis he developed with Andy Clark, which argues that the boundaries of the mind are not fixed at the skull.

  Chalmers appeared in the 2012 documentary The Singularity by filmmaker Doug Wolens, which examined Ray Kurzweil's proposal for a point in time when computer intelligence exceeds human intelligence. In 2020, he was featured in the Daily Nous series on GPT-3, which he described as one of the most interesting and important AI systems ever produced. By 2023, he had turned his attention directly to the question of whether large language models could be conscious. His tentative answer was probably not, but he suggested they could become serious candidates for consciousness within a decade.

  That same year, a bet he had made in 1998 with neuroscientist Christof Koch came due. Chalmers had wagered a case of wine that the neural underpinnings of consciousness would not be resolved by 2023. Koch had bet that they would. Chalmers won.

• 7. Institutional Presence

  ›

  Chalmers co-founded PhilPapers with David Bourget, a database of journal articles used by philosophers across the discipline. He serves as an editor on philosophy of mind topics for the Stanford Encyclopedia of Philosophy, one of the field's primary reference works.

  He co-organizes what began as the Toward a Science of Consciousness conference with Stuart Hameroff, later renamed The Science of Consciousness, though he eventually stepped away when he felt it had moved too far from mainstream science. He is a founding member of the Association for the Scientific Study of Consciousness and a past president of that organization. In 2006, he was elected a fellow of the Australian Academy of the Humanities. In 2013, he joined the American Academy of Arts and Sciences. In May 2018, he was named to the jury for the Berggruen Prize.

  At NYU, where he accepted a part-time post in 2009 and became full-time in 2014, he serves alongside Ned Block as co-director of the Center for Mind, Brain and Consciousness. He also held the directorship of the Center for Consciousness at the Australian National University, where an ARC Federation Fellowship drew him back to Australia in 2004. For anyone tracking the long arc of his career, that fellowship brought him full circle to the continent where he grew up, coded on a PDP-10 as a child, and first read Hofstadter at 13.