it also has three possible “colors,” and one times two times three is six. Pho-
30
tons have an electric charge fixed at zero, but they do have two possible spin
31
states, so they have two degrees of freedom just like electrons do.
32
We could interpret the supposed existence of mental properties in the
33
most direct way possible, as introducing new degrees of freedom for each
34
elementary particle. In addition to spinning clockwise or counterclockwise,
35S
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
01
of the most basic things we know about the Core Theory is exactly how
02
many degrees of freedom each particle has. Recall the Feynman diagrams
03
from chapter 23, describing particles scattering off of one another by ex-
04
changing other particles. Each diagram corresponds to a number that we
05
can compute, the total contribution of that particular process to the end
06
result, such as two electrons scattering off of each other by exchanging pho-
07
tons. Those numbers have been experimentally tested to exquisite precision,
08
and the Core Theory has passed with flying colors.
09
A crucial ingredient in calculating these processes is the number of de-
10
grees of freedom associated with each particle. If photons had some hidden
11
degrees of freedom that we didn’t know about, they would alter all of the
12
predictions we make for any scattering experiment that involves such pho-
13
tons, and all of our predictions would be contradicted by the data. That
14
doesn’t happen. So we can state unambiguously that photons do not come
15
in “happy” and “sad” varieties, or any other manner of mental properties
16
that act like physical degrees of freedom.
17
Advocates of panpsychism would probably not go as far as to imagine
18
that mental properties play roles similar to true physical degrees of freedom,
19
so that the preceding argument wouldn’t dissuade them. Otherwise these
20
new properties would just be ordinary physical properties.
21
That leaves us in a position very similar to the zombie discussion: we
22
posit new mental properties, and then insist that they have no observable
23
physical effects. What would the world be like if we replaced “protocon-
24
scious photons” with “zombie photons” lacking such mental properties? As
25
far as the behavior of physical matter is concerned, including what you say
26
when you talk or write or communicate nonverbally with your romantic
27
partner, the zombie- photon world would be exactly the same as the world
28
where photons have mental properties.
29
A good Bayesian can therefore conclude that the zombie- photon world
30
is the one we actually live in. We simply don’t gain anything by attributing
31
the features of consciousness to individual particles. Doing so is not a useful
32
way of talking about the world; it buys us no new insight or predictive
33
power. All it does is add a layer of metaphysical complication onto a descrip-
34
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
02
representing themselves and the world within their inner states. Just be-
03
cause it is here full- blown in our contemporary universe doesn’t mean that
04
there was always some trace of it from the very start. Some things just come
05
into being as the universe evolves and entropy and complexity grow: galax-
06
ies, planets, organisms, consciousness.
07
•
08
09
Regardless of whether individual particles possess a form of protoconscious
10
awareness, there is a long history of attempts to link the mystery of con-
11
sciousness to another famous mystery, that of quantum mechanics. In part
12
these efforts can be attributed to what Chalmers has jokingly called the
13
“Law of Minimization of Mystery”: consciousness is confusing, and quan-
14
tum mechanics is confusing, so maybe they’re somehow related.
15
There is no doubt that there are real mysteries associated with quantum
16
mechanics, especially what precisely happens when an observer measures a
17
quantum system. In Everett’s Many- Worlds Interpretation, the answer is
18
simple: nothing special. Everything continues to smoothly evolve according
19
to a deterministic set of equations, but the interaction of the macroscopic
20
observer with a vast environment around them causes the way we talk
21
about the system to evolve from “one universe in a quantum superposition”
22
to “two separate universes.” The fact that observers happen to be con-
23
scious plays precisely zero role; measurements can be easily carried out by
24
nematodes, video cameras, or rocks.
25
Sadly, not everyone accepts the advantages of this approach. In the text-
26
book version of quantum mechanics, there is a moment during the observa-
27
tion process at which wave functions “collapse.” Before collapse, a particle
28
might have been in a superposition of two different states, like spinning
29
clockwise and spinning counterclockwise; after collapse, only one alterna-
30
tive remains. So what precisely leads to the collapse event? It is not com-
31
pletely crazy to speculate that it might have something to do with the
32
presence of a conscious observer, and a number of respectable physicists
33
have done so over the years.
34
The possibility that consciousness plays a role in understanding quan-
35S
tum mechanics has lost almost all of whatever support it may have on
ce
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enjoyed. These days we understand quantum mechanics a lot better than
01
the pioneers did; we have very specific and quantitative theories that can
02
plausibly explain exactly what happens during the process of measurement,
03
without any need to invoke consciousness. We don’t know which if any of
04
these theories is right, so mysteries remain— but even without having the
05
final answer, the very existence of respectable alternatives tends to make the
06
way- out ones seem less attractive.
07
Some people have an inordinate fondness for way- out possibilities, and
08
will grab on to their associated buzzwords and use them for their own ends.
09
Such is the situation with most of what goes by the label of “quantum con-
10
sciousness” in popular conversation. Quantum mechanics says that super-
11
positions evolve into definite outcomes during the process of measurement,
12
at least for any one observer; it’s not hard to twist that into the claim that
13
conscious observation literally brings reality into existence.
14
It’s the ultimate anti- Copernican move, a way of restoring the central
15
importance of humanity to our picture of the universe. Sure, you might feel
16
insignificant in the vastness of the cosmos, and perhaps you become alien-
17
ated by thinking that your atoms obey impersonal laws of physics, but hey,
18
don’t worry: you are personally creating the world at every moment, just by
19
looking at it. Advocates of this approach will sometimes throw in some-
20
thing about “entanglement”— which isn’t even a mystery, just an interesting
21
feature of quantum mechanics— to make you feel like you are connected to
22
everything else in the universe. As a final flourish, they might suggest that
23
quantum mechanics has discarded the physical world entirely, leaving us
24
with idealism, where everything is a projection of the mind.
25
There is nothing in anything we know about physics that suggests any
26
of that is true. Quantum mechanics may be mysterious, but it is still— in all
27
of its suggested formulations— an ordinary physical theory, governed by
28
impersonal laws expressed in the form of equations. In particular, even in
29
interpretations where wave functions really do collapse when systems are
30
observed, the person doing the observing has no influence whatsoever on
31
what the measurement outcome turns out to be. That just follows a rule, the
32
Born rule for quantum probabilities, which says the probability of each
33
outcome is given by the value of the wave function squared. Nothing
34
spooky, nothing personal, nothing intrinsically human. Just physics.
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01
•
02
03
“Quantum consciousness” in this disreputable formulation is distinct from
04
an idea that is speculative, but at least physically sensible: that quantum
05
processes play an important role in the actual workings of the brain. At
06
some level this is trivially true. The brain is made of particles, which are
07
vibrations of quantum fields, which obey the rules of quantum mechanics.
08
But most neuroscience starts with the assumption that important processes
09
in the brain are well described by the approximation of classical physics. We
10
don’t need wave functions or entanglement to get a rocket to the moon, and
11
it seems reasonable to imagine that we don’t need them to understand the
12
brain either.
13
The brain is a warm, wet environment, not a cold, precise laboratory
14
setup. Every particle in your head is constantly being jostled by other par-
15
ticles, leading to an ongoing process of “collapse” (or branching of the wave
16
function, for fearless Everettians like me). There’s not much time for par-
17
ticles to linger in a superposition, become entangled with other particles,
18
and so on. Maintaining quantum coherence inside the brain would seem to
19
be analogous to building a house of cards outside during a hurricane.
20
Nevertheless, recent discoveries in biology have indicated that living
21
organisms do seem to take advantage of certain quantum effects that go
22
beyond what classical physics could do. Photosynthesis, in particular, in-
23
volves transfers of energy by particles in quantum superposition. (Darwin-
24
ian evolution stumbled across quantum mechanics long before human
25
beings discovered it.) So we can’t discard the possibility that quantum ef-
26
fects are important in the brain simply on the basis of pure thought— we
27
have to do the usual empiricist Bayesian procedure of inventing hypotheses
28
and testing them against the data.
29
Physicist Matthew Fisher has identified one very specific set of quantum
30
objects in the brain that could become entangled with one another, and
31
remain so for a relatively long time: the nuclei of certain phosphorous atoms
32
that are found in subgroups of ATP molecules and elsewhere. In Fisher’s
33
model, the rate at which chemical reactions involving these atoms will oc-
34
cur depends on whether their nuclei share quantum entanglement with
35S
other nearby phosphorous nuclei. As a result, quantum mechanics could
36N
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
01
ideas. They do remind us not to jump to conclusions when we’re talking
02
about a system as subtle and complicated as a brain.
03
When most people think of quantum effects in the brain, however,
04
they’re not imagining something as prosaic as accounting for how the brain
05
performs computations. They want to invoke new physics to help us explain
06
consciousness.
07
The most famous proponent of this approach is Roger Penrose, the Brit-
08
ish physicist and mathematician renowned for his contributions to our
09
modern understanding of Einstein’s general relativity. Penrose is one of
10
those scientists who rattles off brilliant ideas like most of us brush bread
11
crumbs from our shirts. And he is convinced that human brains do things
12
that computers can’t do. But computers can simulate anything that could
13
happen according to the known laws of physics. So we need some genuinely
14
new physical phenomena at work in the brain— in particular, something
15
special about the collapse of the wave function.
16
Penrose’s argument is elaborate and ingenious, but ultimately uncon-
17
vincing to the vast majority of researchers studying physics, neuroscience,
18
or consciousness. He starts with Gödel’s Incompleteness Theorem, a cele-
19
brated result by Austrian logician Kurt Gödel. At the risk of dramatic over-
20
simplification, the gist of the Incompleteness Theorem is that within any
21
consistent mathematical formal system— a set of axioms, and rules for de-
22
riving consequences from them— there will be statements that are true but
23
cannot be proven within that system. (Gödel’s basic trick was to invent a
24
way of expressing “This statement cannot be proven” within any sufficiently
25
powerful formal system. Either you can prove it and it is therefore false,
26
showing that your system is inconsistent, or you can’t prove it and it’s true.)
27
A computer working with the appropriate set of formal rules wouldn’t be
28
able to prove such a statement.
29
But, Penrose says, human mathematicians have no trouble perceiving
30
the truth of statements like that. Therefore, what’s going on inside the brain
31
of a human mathematician must be something over and above a formal
32
mathematical system. The known laws of physics don’t grant us such
33
powers.
34
As we discussed in chapter 24, if there is going to be a loophole in the
S35
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
The Big Picture Page 62