The Big Picture
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it also has three possible “colors,” and one times two times three is six. Pho-
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tons have an electric charge fixed at zero, but they do have two possible spin
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states, so they have two degrees of freedom just like electrons do.
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We could interpret the supposed existence of mental properties in the
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most direct way possible, as introducing new degrees of freedom for each
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elementary particle. In addition to spinning clockwise or counterclockwise,
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a photon could be in one of (let’s say) two mental states. Call them “happy”
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and “sad,” although the labels are more poetic than authentic.
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This overly literal version of panpsychism cannot possibly be true. One
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of the most basic things we know about the Core Theory is exactly how
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many degrees of freedom each particle has. Recall the Feynman diagrams
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from chapter 23, describing particles scattering off of one another by ex-
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changing other particles. Each diagram corresponds to a number that we
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can compute, the total contribution of that particular process to the end
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result, such as two electrons scattering off of each other by exchanging pho-
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tons. Those numbers have been experimentally tested to exquisite precision,
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and the Core Theory has passed with flying colors.
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A crucial ingredient in calculating these processes is the number of de-
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grees of freedom associated with each particle. If photons had some hidden
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degrees of freedom that we didn’t know about, they would alter all of the
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predictions we make for any scattering experiment that involves such pho-
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tons, and all of our predictions would be contradicted by the data. That
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doesn’t happen. So we can state unambiguously that photons do not come
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in “happy” and “sad” varieties, or any other manner of mental properties
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that act like physical degrees of freedom.
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Advocates of panpsychism would probably not go as far as to imagine
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that mental properties play roles similar to true physical degrees of freedom,
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so that the preceding argument wouldn’t dissuade them. Otherwise these
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new properties would just be ordinary physical properties.
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That leaves us in a position very similar to the zombie discussion: we
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posit new mental properties, and then insist that they have no observable
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physical effects. What would the world be like if we replaced “protocon-
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scious photons” with “zombie photons” lacking such mental properties? As
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far as the behavior of physical matter is concerned, including what you say
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when you talk or write or communicate nonverbally with your romantic
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partner, the zombie- photon world would be exactly the same as the world
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where photons have mental properties.
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A good Bayesian can therefore conclude that the zombie- photon world
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is the one we actually live in. We simply don’t gain anything by attributing
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the features of consciousness to individual particles. Doing so is not a useful
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way of talking about the world; it buys us no new insight or predictive
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power. All it does is add a layer of metaphysical complication onto a descrip-
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tion that is already perfectly successful.
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Consciousness seems to be an intrinsically collective phenomenon, a
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way of talking about the behavior of complex systems with the capacity for
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representing themselves and the world within their inner states. Just be-
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cause it is here full- blown in our contemporary universe doesn’t mean that
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there was always some trace of it from the very start. Some things just come
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into being as the universe evolves and entropy and complexity grow: galax-
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ies, planets, organisms, consciousness.
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Regardless of whether individual particles possess a form of protoconscious
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awareness, there is a long history of attempts to link the mystery of con-
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sciousness to another famous mystery, that of quantum mechanics. In part
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these efforts can be attributed to what Chalmers has jokingly called the
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“Law of Minimization of Mystery”: consciousness is confusing, and quan-
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tum mechanics is confusing, so maybe they’re somehow related.
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There is no doubt that there are real mysteries associated with quantum
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mechanics, especially what precisely happens when an observer measures a
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quantum system. In Everett’s Many- Worlds Interpretation, the answer is
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simple: nothing special. Everything continues to smoothly evolve according
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to a deterministic set of equations, but the interaction of the macroscopic
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observer with a vast environment around them causes the way we talk
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about the system to evolve from “one universe in a quantum superposition”
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to “two separate universes.” The fact that observers happen to be con-
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scious plays precisely zero role; measurements can be easily carried out by
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nematodes, video cameras, or rocks.
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Sadly, not everyone accepts the advantages of this approach. In the text-
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book version of quantum mechanics, there is a moment during the observa-
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tion process at which wave functions “collapse.” Before collapse, a particle
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might have been in a superposition of two different states, like spinning
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clockwise and spinning counterclockwise; after collapse, only one alterna-
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tive remains. So what precisely leads to the collapse event? It is not com-
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pletely crazy to speculate that it might have something to do with the
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presence of a conscious observer, and a number of respectable physicists
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have done so over the years.
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The possibility that consciousness plays a role in understanding quan-
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tum mechanics has lost almost all of whatever support it may have on
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enjoyed. These days we understand quantum mechanics a lot better than
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the pioneers did; we have very specific and quantitative theories that can
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plausibly explain exactly what happens during the process of measurement,
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without any need to invoke consciousness. We don’t know which if any of
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these theories is right, so mysteries remain— but even without having the
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final answer, the very existence of respectable alternatives tends to make the
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way- out ones seem less attractive.
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Some people have an inordinate fondness for way- out possibilities, and
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will grab on to their associated buzzwords and use them for their own ends.
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Such is the situation with most of what goes by the label of “quantum con-
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sciousness” in popular conversation. Quantum mechanics says that super-
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positions evolve into definite outcomes during the process of measurement,
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at least for any one observer; it’s not hard to twist that into the claim that
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conscious observation literally brings reality into existence.
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It’s the ultimate anti- Copernican move, a way of restoring the central
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importance of humanity to our picture of the universe. Sure, you might feel
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insignificant in the vastness of the cosmos, and perhaps you become alien-
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ated by thinking that your atoms obey impersonal laws of physics, but hey,
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don’t worry: you are personally creating the world at every moment, just by
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looking at it. Advocates of this approach will sometimes throw in some-
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thing about “entanglement”— which isn’t even a mystery, just an interesting
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feature of quantum mechanics— to make you feel like you are connected to
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everything else in the universe. As a final flourish, they might suggest that
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quantum mechanics has discarded the physical world entirely, leaving us
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with idealism, where everything is a projection of the mind.
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There is nothing in anything we know about physics that suggests any
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of that is true. Quantum mechanics may be mysterious, but it is still— in all
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of its suggested formulations— an ordinary physical theory, governed by
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impersonal laws expressed in the form of equations. In particular, even in
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interpretations where wave functions really do collapse when systems are
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observed, the person doing the observing has no influence whatsoever on
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what the measurement outcome turns out to be. That just follows a rule, the
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Born rule for quantum probabilities, which says the probability of each
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outcome is given by the value of the wave function squared. Nothing
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spooky, nothing personal, nothing intrinsically human. Just physics.
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“Quantum consciousness” in this disreputable formulation is distinct from
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an idea that is speculative, but at least physically sensible: that quantum
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processes play an important role in the actual workings of the brain. At
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some level this is trivially true. The brain is made of particles, which are
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vibrations of quantum fields, which obey the rules of quantum mechanics.
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But most neuroscience starts with the assumption that important processes
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in the brain are well described by the approximation of classical physics. We
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don’t need wave functions or entanglement to get a rocket to the moon, and
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it seems reasonable to imagine that we don’t need them to understand the
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brain either.
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The brain is a warm, wet environment, not a cold, precise laboratory
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setup. Every particle in your head is constantly being jostled by other par-
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ticles, leading to an ongoing process of “collapse” (or branching of the wave
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function, for fearless Everettians like me). There’s not much time for par-
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ticles to linger in a superposition, become entangled with other particles,
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and so on. Maintaining quantum coherence inside the brain would seem to
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be analogous to building a house of cards outside during a hurricane.
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Nevertheless, recent discoveries in biology have indicated that living
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organisms do seem to take advantage of certain quantum effects that go
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beyond what classical physics could do. Photosynthesis, in particular, in-
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volves transfers of energy by particles in quantum superposition. (Darwin-
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ian evolution stumbled across quantum mechanics long before human
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beings discovered it.) So we can’t discard the possibility that quantum ef-
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fects are important in the brain simply on the basis of pure thought— we
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have to do the usual empiricist Bayesian procedure of inventing hypotheses
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and testing them against the data.
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Physicist Matthew Fisher has identified one very specific set of quantum
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objects in the brain that could become entangled with one another, and
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remain so for a relatively long time: the nuclei of certain phosphorous atoms
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that are found in subgroups of ATP molecules and elsewhere. In Fisher’s
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model, the rate at which chemical reactions involving these atoms will oc-
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cur depends on whether their nuclei share quantum entanglement with
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other nearby phosphorous nuclei. As a result, quantum mechanics could
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play a very real role in brain processes, perhaps even allowing the brain to
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act as a “quantum computer.” Or not— these are all new and speculative
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ideas. They do remind us not to jump to conclusions when we’re talking
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about a system as subtle and complicated as a brain.
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When most people think of quantum effects in the brain, however,
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they’re not imagining something as prosaic as accounting for how the brain
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performs computations. They want to invoke new physics to help us explain
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consciousness.
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The most famous proponent of this approach is Roger Penrose, the Brit-
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ish physicist and mathematician renowned for his contributions to our
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modern understanding of Einstein’s general relativity. Penrose is one of
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those scientists who rattles off brilliant ideas like most of us brush bread
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crumbs from our shirts. And he is convinced that human brains do things
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that computers can’t do. But computers can simulate anything that could
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happen according to the known laws of physics. So we need some genuinely
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new physical phenomena at work in the brain— in particular, something
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special about the collapse of the wave function.
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Penrose’s argument is elaborate and ingenious, but ultimately uncon-
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vincing to the vast majority of researchers studying physics, neuroscience,
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or consciousness. He starts with Gödel’s Incompleteness Theorem, a cele-
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brated result by Austrian logician Kurt Gödel. At the risk of dramatic over-
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simplification, the gist of the Incompleteness Theorem is that within any
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consistent mathematical formal system— a set of axioms, and rules for de-
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riving consequences from them— there will be statements that are true but
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cannot be proven within that system. (Gödel’s basic trick was to invent a
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way of expressing “This statement cannot be proven” within any sufficiently
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powerful formal system. Either you can prove it and it is therefore false,
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showing that your system is inconsistent, or you can’t prove it and it’s true.)
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A computer working with the appropriate set of formal rules wouldn’t be
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able to prove such a statement.
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But, Penrose says, human mathematicians have no trouble perceiving
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the truth of statements like that. Therefore, what’s going on inside the brain
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of a human mathematician must be something over and above a formal
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mathematical system. The known laws of physics don’t grant us such
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powers.
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As we discussed in chapter 24, if there is going to be a loophole in the
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audacious claim that the laws of physics underlying everyday life are
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completely known, the leading candidate would be some alteration in how