Thursday, February 3, 2022

Does the Brain Cause Consciousness? Part 2

Is there an afterlife?  Can a computer be conscious?  In Part 1, I pointed out that the popular science answers to these questions depend on an often unstated assumption:

Assumption: The brain causes consciousness.

I am going to show in this and subsequent posts why there is very good reason to doubt this assumption, and why it’s almost certainly false.  To do that, I’m going to try to convince you of two statements [1] which, taken together, imply that the brain does not cause consciousness:

1)     A brain can be copied.  (Even if it cannot be done today due to technological limitations, there is no physical law preventing the physical state of a brain from being copied.)

2)     A person’s conscious state cannot be copied.

In today’s post, I’ll address Statement 1.  First of all, I think most people, particularly scientists, would already agree with it.  And since my goal is to convince you, the reader, then if you already agree with it, there’s no need to read further.  Instead, just move on to the next post in this series, where I’ll address Statement 2.

Of course, no one thinks that a brain can be copied today.  But what physical law prevents copying a brain in the future?  The only known physical principle of which I’m aware is the quantum no-cloning theorem, which says that a quantum state cannot be copied.  And a brain, like all things in the universe, is presumably in a quantum state, so in that sense it can never be perfectly copied.  But that doesn’t matter as long as quantum effects are not relevant to the brain and its functions.  In other words, the only thing that would prevent a brain from being copied adequately to replicate consciousness is if consciousness depends on quantum effects. 

For example, if a conscious state depended on quantum entanglements with objects outside the brain, then there is inadequate information in the brain to specify a conscious state.  Quantum entanglement is “nonlocal,” which means that Object A can affect entangled Object B instantaneously, even if they are separated by a large distance, and the effect is not limited by the speed of light.  So if my current conscious state depends at least in part on an event in another galaxy (which we cannot detect until we receive light from the event), then consciousness is nonlocal.  This recent paper argues that consciousness is nonlocal, but I doubt many in the scientific community have taken notice.

Another way that consciousness may depend on quantum effects is if, to copy the brain, you’d have to measure the state of objects in the brain (like neurons) so precisely that the Heisenberg Uncertainty Principle kicks in, and the measurement itself starts changing the brain’s physical state.  For example, Scott Aaronson suggests in this paper that if a brain is “unclonable for fundamental physical reasons,” then that unclonability could be a consequence of quantum no-cloning if the granularity a brain would need to be simulated at in order to duplicate someone’s subjective identity was down to the quantum level. 

In general, though, few scientists believe that consciousness or brain function depend on quantum effects, and most who discuss the possibility are quickly dismissed as mystics or pseudoscientists.[2]  As long as consciousness does not depend on quantum effects, then we don’t need to worry about quantum no-cloning, and there is nothing that would prevent a future engineer from scanning a person’s brain and then reproducing a functional duplicate with the same conscious state.

Are you convinced of Statement 1 yet?… that a brain can be copied in principle?  Maybe you’re still concerned about possible quantum effects.  OK, here’s another argument.

The amount of information that can be contained in a volume of space is limited.  This is called the Bekenstein bound.  It’s a ridiculously large number but it’s still finite.  For example, the Bekenstein bound Wikipedia page calculates that the maximum information necessary to recreate a human brain, including its entire quantum state, is on the order of 10^42 bits (where a single “bit” of information is either a 0 or 1).  That’s a huge number… it looks like 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000, but it’s still much, much smaller than the number of particles in the universe.  Also, the Bekenstein bound for the brain is an upper physical limit that’s based on a brain so dense with information that it’s right on the verge of collapsing into a black hole!  I think it’s reasonable to surmise that we aren’t walking around with potential black holes in our skulls, so the actual information necessary to specify the quantum state of a brain is probably much, much, much, much smaller than 10^42 bits.  But it doesn’t actually matter.  Here’s why.

Even if we can’t in practice copy a human brain, the universe should be able to.  I’m referring to a Boltzmann Brain.  Physicists currently believe that essentially any physical state can be created by randomness (i.e., accident).  So even though it’s extremely unlikely, a physicist will say that there is some chance that atoms and particles will accidentally come together somewhere in the universe to create your brain.  And even if we include quantum effects, and even if that accidental collection of atoms has to specify the 10^42 bits that could potentially be specified in the physical state of your brain, there is some nonzero probability that it will occur. 

In other words, there is no known physical law that will prevent the exact recreation of your brain elsewhere.  The universe can copy your brain, even if your brain’s function depends on quantum effects.  Therefore, a brain can be copied.  Statement 1 is true.

In my next post, I’ll address Statement 2.  As for now, do you have any questions or concerns about Statement 1?

[1] As I mentioned previously, I would ordinarily try to be more precise with my words, arguments, and proofs.  But the purpose of this and subsequent posts is to write more colloquially without alienating lay readers.  Better precision can be found, e.g., in my papers.

[2] Don’t forget that consensus does not equal truth.  There is, and perhaps always has been, a bully culture in science, which is why scientific paradigms tend to be changed only by independent mavericks.


  1. Agreed! In principle, it appears that a brain can be copied. But couldn't the brain be copied, and as you describe above, consciousness be non-local, dependent on quantum entanglements outside of the brain... in some distant galaxy or perhaps in your neighbors house?

    1. No. For example, let's say the state of a neuron in your brain was entangled with the state of an object outside your brain. There is no way to "read" the information in that entanglement simply by looking at the neuron... no matter how good your microscope is. If it turns out that consciousness depends on quantum entanglements with particles and objects beyond the brain, then there is just no way to copy the brain adequately to produce consciousness. This might be made more clear in Part 3 of the blog series...


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