Identity Isn't In Specific Atoms

by Eliezer Yudkowsky6 min read19th Apr 200874 comments

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Physics
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Continuation ofNo Individual Particles
Followup toThe Generalized Anti-Zombie Principle

Suppose I take two atoms of helium-4 in a balloon, and swap their locations via teleportation.  I don't move them through the intervening space; I just click my fingers and cause them to swap places.  Afterward, the balloon looks just the same, but two of the helium atoms have exchanged positions.

Now, did that scenario seem to make sense?  Can you imagine it happening?

If you looked at that and said, "The operation of swapping two helium-4 atoms produces an identical configuration—not a similar configuration, an identical configuration, the same mathematical object—and particles have no individual identities per se—so what you just said is physical nonsense," then you're starting to get quantum mechanics.

If you furthermore had any thoughts about a particular "helium atom" being a factor in a subspace of an amplitude distribution that happens to factorize that way, so that it makes no sense to talk about swapping two identical multiplicative factors, when only the combined amplitude distribution is real, then you're seriously starting to get quantum mechanics.

If you thought about two similar billiard balls changing places inside a balloon, but nobody on the outside being able to notice a difference, then... oh, hell, I don't know, go back to the beginning of the series and try rereading the whole thing over the course of one day.  If that still doesn't work, read an actual book on quantum mechanics.  Feynman's QED is a great place to start—though not a good place to finish, and it's not written from a pure realist perspective.

But if you did "get" quantum physics, then, as promised, we have now come to the connection between the truth of quantum mechanics, the lies of human intuitions, and the Generalized Anti-Zombie Principle.

Stirling Westrup previously commented, on the GAZP post:

I found the previous articles on Zombies somewhat tedious... Still, now I'm glad I read through it all as I can see why you were so careful to lay down the foundations you did.

The question of what changes one can make to the brain while maintaining 'identity' has been been discussed many times on the Extropians list, and seldom with any sort of constructive results.

Today's article has already far exceeded the signal to noise ratio of any other discussion on the same topic that I've ever seen...

The Extropians email list that Westrup refers to, is the oldest online gathering place of transhumanists.  It is where I made my debut as a writer, and it is where the cofounders of the Singularity Institute met.  Though the list is not what it once was...

There are certain topics, on the Extropians list, that have been discussed over and over again, for years and years, without making any progress.  Just the same arguments and counterarguments, over and over again.

The worst of those infinite loops concerns the question of personal identity.  For example, if you build an exact physical replica of a human, using different atoms, but atoms of the same kind in the same places, is it the same person or just a copy? 

This question has flared up at least once a year, always with the same arguments and counterarguments, every year since I joined the Extropians mailing list in 1996.  And I expect the Personal Identity Wars started well before then.

I did try remarking, "Quantum mechanics says there isn't any such thing as a 'different particle of the same kind', so wherever your personal identity is, it sure isn't in particular atoms, because there isn't any such thing as a 'particular atom'."

It didn't work, of course.  I didn't really expect it to.  Without a long extended explanation, a remark like that doesn't actually mean anything.

The concept of reality as a sum of independent individual billiard balls, seems to be built into the human parietal cortex—the parietal cortex being the part of our brain that does spatial modeling: navigating rooms, grasping objects, throwing rocks.

Even very young children, infants, look longer at a scene that violates expectations—for example, a scene where a ball rolls behind a screen, and then two balls roll out.

People try to think of a person, an identity, an awareness, as though it's an awareness-ball located inside someone's skull.  Even nonsophisticated materialists tend to think that, since the consciousness ball is made up of lots of little billiard balls called "atoms", if you swap the atoms, why, you must have swapped the consciousness.

Now even without knowing any quantum physics—even in a purely classical universe—it is possible to refute this idea by applying the Generalized Anti-Zombie Principle.  There are many possible formulations of the GAZP, but one of the simpler ones says that, if alleged gigantic changes are occurring in your consciousness, you really ought to notice something happening, and be able to say so.

The equivalent of the Zombie World, for questions of identity/continuity, is the Soul Swap World.  The allegation is that the Soul Swap World is microphysically identical to our own; but every five minutes, each thread of consciousness jumps to a random new brain, without the brains changing in any third-party experimentally detectable way.  One second you're yourself, the next second you're Britney Spears.  And neither of you say that you've noticed anything happening—by hypothesis, since you're microphysically identical down to the motion of your lips.

(Let me know if the Soul Swap World has been previously invented in philosophy, and has a standard name—so far as I presently know, this is my own idea.)

We can proceed to demolish the Soul Swap World by an argument exactly analogous to the one that demolished the Zombie World:  Whatever-it-is which makes me feel that I have a consciousness that continues through time, that whatever-it-is was physically potent enough to make me type this sentence.  Should I try to make the phrase "consciousness continuing through time" refer to something that has nothing to do with the cause of my typing those selfsame words, I will have problems with the meaning of my arguments, not just their plausibility.

Whatever it is that makes me say, aloud, that I have a personal identity, a causally closed world physically identical to our own, has captured that source—if there is any source at all.

And we can proceed, again by an exactly analogous argument, to a Generalized Anti-Swapping Principle:  Flicking a disconnected light switch shouldn't switch your personal identity, even though the motion of the switch has an in-principle detectable gravitational effect on your brain, because the switch flick can't disturb the true cause of your talking about "the experience of subjective continuity".

So even in a classical universe, if you snap your fingers and swap an atom in the brain for a physically similar atom outside; and the brain is not disturbed, or not disturbed any more than the level of thermal noise; then whatever causes the experience of subjective continuity, should also not have been disturbed.  Even if you swap all the classical atoms in a brain at the same time, if the person doesn't notice anything happen, why, it probably didn't.

And of course there's the classic (and classical) argument, "Well, your body's turnover time for atoms is seven years on average."

But it's a moot argument.

We don't live in a classical universe.

We live in a quantum universe where the notion of "same hydrogen atom vs. different hydrogen atom" is physical nonsense.

We live in a universe where the whole notion of billiard balls bopping around is fundamentally wrong.

This can be a disorienting realization, if you formerly thought of yourself as an awareness ball that moves around.

Sorry.  Your parietal cortex is fooling you on this one.

But wait!  It gets even worse!

The brain doesn't exactly repeat itself; the state of your brain one second from now is not the state of your brain one second ago.  The neural connections don't all change every second, of course.  But there are enough changes every second that the brain's state is not cyclic, not over the course of a human lifetime.  With every fragment of memory you lay down—and every thought that pops in and out of short-term memory—and every glance of your eyes that changes the visual field of your visual cortex—you ensure that you never repeat yourself exactly.

Over the course of a single second—not seven years, but one second—the joint position of all the atoms in your brain, will change far enough away from what it was before, that there is no overlap with the previous joint amplitude distribution.  The brain doesn't repeat itself.  Over the course of one second, you will end up being comprised of a completely different, nonoverlapping volume of configuration space.

And the quantum configuration space is the most fundamental known reality, according to our best current theory, remember.  Even if quantum theory turns out not to be really truly fundamental, it has already finished superseding the hallucination of individual particles.  We're never going back to billiard balls, any more than we're going back to Newtonian mechanics or phlogiston theory.  The ratchet of science turns, but it doesn't turn backward.

And actually, the time for you to be comprised of a completely different volume of configuration space, is way less than a second.  That time is the product of all the individual changes in your brain put together.  It'll be less than a millisecond, less than a femtosecond, less than the time it takes light to cross a neutron diameter.  It works out to less than the Planck time, if that turns out to make physical sense.

And then there's the point to consider that the physically real amplitude distribution is over a configuration space of all the particles in the universe.  "You" are just a factored subspace of that distribution.

Yes, that's right, I'm calling you a factored subspace.

None of this should be taken as saying that you are somehow independent of the quantum physics comprising you.  If an anvil falls on your head, you will stop talking about consciousness.  This is experimentally testable.  Don't try it at home.

But the notion that you can equate your personal continuity, with the identity of any physically real constituent of your existence, is absolutely and utterly hopeless.

You are not "the same you, because you are made of the same atoms".  You have zero overlap with the fundamental constituents of yourself from even one nanosecond ago.  There is continuity of information, but not equality of parts.

The new factor over the subspace looks a whole lot like the old you, and not by coincidence:  The flow of time is lawful, there are causes and effects and preserved commonalities.  Look to the regularity of physics, if you seek a source of continuity.  Do not ask to be composed of the same objects, for this is hopeless.

Whatever makes you feel that your present is connected to your past, it has nothing to do with an identity of physically fundamental constituents over time.

Which you could deduce a priori, even in a classical universe, using the Generalized Anti-Zombie Principle.  The imaginary identity-tags that read "This is electron #234,567..." don't affect particle motions or anything else; they can be swapped without making a difference because they're epiphenomenal.  But since this final conclusion happens to be counterintuitive to a human parietal cortex, it helps to have the brute fact of quantum mechanics to crush all opposition.

Damn, have I waited a long time to be able to say that.

And no, this isn't the only point I have to make on how counterintuitive physics rules out intuitive conceptions of personal identity.  I've got even stranger points to make.  But those will take more physics first.

 

Part of The Quantum Physics Sequence

Next post: "Three Dialogues on Identity"

Previous post: "No Individual Particles"

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Isn't each particle or amplitude configuration unique because only it has its exact relationship to every other amplitude configuration in the universe? Doesn't that sufficiently make each amplitude configuration at a specific spatial-temporal locality different from every other one, in that the universe can "tell" one from the other?

Wiseman, there's only one amplitude distribution. One. Not two. Not three. One, in all the physics we know.

Occasionally you can approximate interacting blobs of amplitude within that distribution, as the product of several almost-independent subspaces; but this is a mere convenience of computation, it is not the truth.

"Suppose I take two atoms of helium-4 in a balloon, and swap their locations via teleportation." Even a billiard ball-ist might complain you haven't swapped their momentums. You might also have to swap the excitation levels of the electrons, protons and gluons, to get a situation that is the same as far as our physics understands.

Over already? I thought we'd hear about many worlds, measure theory, decoherence, and Julian Barbour before we came to the end.

If this is the end, then it's time to evaluate the picture we've been given. Basically, it's nonsense. This is not particularly Eliezer's fault. As a sketch of how quantum mechanics works, it is accurate, and since quantum mechanics is generally not held to be in need of explanation itself, to some degree it has the imprimatur of orthodoxy as a sketch of reality itself. But that just means it is officially sanctioned nonsense.

Let's... (read more)

Over already? I thought we'd hear about many worlds, measure theory, decoherence, and Julian Barbour before we came to the end.

No, not over. Yes, the plan calls for Heisenberg, decoherence, many worlds, and Barbour.

I'll sit down and let the second act begin, then. :-)

"If you furthermore had any thoughts about a particular "helium atom" being a factor in a subspace of an amplitude distribution that happens to factorize that way,"

If a helium atom is just an accidential, temporary factorization of an amplitude distribution, then why does it keep appearing over and over again when we look at the universe? If you throw a thousand electrons together, let them interact, zap them with laser radiation, etc., etc., at the end of the day you will still see a bunch of electrons with 511 keV rest mass and -1 cha... (read more)

If that still doesn't work, read an actual book on quantum mechanics. Feynman's QED is a great place to start..

Since I was pretty much lost after the first few posts in this series, this is exactly what I am doing. I've gone through the first 2 chapters, and what has surprised me is that at least one part of it (explaining why light "bends" when it goes through a material with a different refractive index) has been MORE intuitive to me than the "classical" explanation. The explanation (or shall I say, analogy) I have always heard is th... (read more)

Wiseman, there's only one amplitude distribution. One. Not two. Not three. One, in all the physics we know.

I do understand this Eliezer. But my point is even though it's just one distribution, there is still a description of differentation within that one distribution, otherwise the universe would be just one electron, or something like that. So since there is differentation within the distribution, and since those differentations are tracked and consistent due to the non-random laws of this universe, isn't that really the same as "identity", in that the "differentations" are always 100% unique?

I don't know a standard name for it, but the soul-swap issue is quite old. Locke is interpreted as making some similar point in chapter XXVII, section 13 of the Essay Concerning Human Understanding; I know I always hear the point attributed to Locke, so he may be the first.

Eliezer has the same problem here as with the zombie argument. The point isn't that there are zombie worlds, or soul swap worlds. Saying that something is logically possible is nowhere near saying that something is actual. It is logically possible for someone to be kidnapped, have his brain placed in a vat, and information fed in producing the impression that his experiences are in precise continuity with his experiences the day before being kidnapped. Of course, he will have no way to notice this. In fact, it is logically possible that that this just happ... (read more)

I actually agree with the reductionist view about personal identity, though of course for very different reasons from Eliezer. (I think that identity-swapping is strictly inconceivable. There is no difference there in what the world is like, in stark contrast to the zombie or BIV case where we can understand the (albeit undetectable) difference in how things are.)

Likewise, the soul swap world, and the zombie world, are highly improbable. This is no reason at all to call them logically impossible.

That isn't why he's calling them logically impossible. It's the self-contradictions inherent in their definitions that causes him to reject those ideas.

Eliezer makes many errors. That is not one of them.

Suppose I take two atoms of helium-4 in a balloon, and swap their locations via teleportation.

For a book version, you will definitely want to be more precise here. I assumed they were in different quantum states (this seems a very reasonable assumption failing a specification to the contrary). Perhaps they had different spins, energies, momenta, etc. This means that the swapping did make sense.

Anonymous, you don't seem to understand the reductionist thesis: the claim is that there isn't any consciousness-stuff; it only seems like it because we're stupid—which is also a remarkable claim, in its own way, but it beats the alternatives.

Unknown: "[...] then he is infinitely certain about it [...]"

Really?—cf. "Infinite Certainty" and "0 and 1 Are Not [...]"

Thinking that something is logically impossible doesn't imply infinite certainty if we permit impossible possible worlds.

"Anonymous, you don't seem to understand the reductionist thesis: the claim is that there isn't any consciousness-stuff; it only seems like it because we're stupid—which is also a remarkable claim, in its own way, but it beats the alternatives."

It beats the alternative that "we don't know enough to make a claim right now"? For example, I think that's the leading claim about what preceded or sparked the big bang, beating out other 'remarkable' claims like that we're in an infinite cycle of big bangs, that our big bang resulted from a bla... (read more)

This has been a fascinating series of posts. You are suggesting a realistic interpretation of QM. Do you take the real universe to be the (single) point in the universal QM configuration space, along with the single complex value of the universal wavefunction? Or, since the wavefunction is a function of all possible configurations, are those other configurations somehow real as well (which would be some sort of multiverse theory)? Quantum mechanics certainly allows wavefunctions comprising superpositions of different configurations. Are these superposition states not fundamental?

0xrchz11yNo, the universe is an (evolving) amplitude distribution over configuration space. I'm not what "superposition state" means, but my guess is that the answer to "Are these superposition states not fundamental?" is "Yes they are".

And I expect the Personal Identity Wars started well before then.

No later than 1987.

I've a new post - 'Non-causal Talk' - which points out some problems with Eliezer's assumption that our words refer to whatever causes us to utter them.

No, Richard. Just... no.

How can you have missed the point that badly?

The equivalent of the Zombie World, for questions of identity/continuity, is the Soul Swap World. The allegation is that the Soul Swap World is microphysically identical to our own; but every five minutes, each thread of consciousness jumps to a random new brain, without the brains changing in any third-party experimentally detectable way. One second you're yourself, the next second you're Britney Spears.

This scenario strikes me as logically incoherent - for much the same reason as I don't buy "body swap" scenarios in science fiction.

There i... (read more)

3shokwave10yThat is the intended conclusion from the Soul Swap World thought-experiment.

The short answer is that while we know QM is incomplete, we equally know that it all has to add up to normality -- meaning among other things that QM results, including the weird ones, have to be explainable by the underlying mechanics.

This is not an answer. We need explanations for observed events, to be sure, but it's far from clear that we need QM explanations. After all, buying the QM explanations of the observed events means giving up all the GR explanations of the observed events.

We're not going to discover some result in the future that'll

... (read more)
[-][anonymous]9y -1

If an anvil falls on your head, you will stop talking about consciousness. This is experimentally testable. Don't try it at home.

Not experimentally testable. Where did all the anvils go?

[This comment is no longer endorsed by its author]Reply

Well I've finally gotten to this point in the series and I have to say how strange it is to have worked through a ton of very hairy quantum physics (which I still don't fully understand, not really, not by a long shot) ... only to have it utilized to bring down a hammer on a thoroughly stupid philosophical argument. Feels a little like using a car crusher to pop a balloon. But the ride has been enjoyable. Thanks.

7khafra9yThe way I look at this sequence is, after building the car crusher and using it to pop the balloon, you still own a brand new car crusher. That's pretty cool.

Before when I was still contemplating whether consciousness had a non-physical component, well before I discovered coherent philosophy or rationalism, I had a similar "soul swap world" idea. It eventually let me discard the idea of a soul, but I still favoured some kind of non-personal consciousness. This idea eventually became that there was a "consciousness field" permeating space which produced the phenomenon, through interaction with our brains through a physical yet unknown mechanism. I thought it some very subtle physical effect we hadn't noticed yet, not really supernatural.

It was progress.

It works out to less than the Planck time, if that turns out to make physical sense.

Is this true for all systems (rock, water, etc?) (ie.. is consciousness some singularity in configuration complexity for some given subset of space?)

I never seen anyone bragging about defeating strawmans so much. Hell, in one place he explicitly said about "Soul Swap World" that he made up on spot to happily destroy.

And I still do not know what I am supposed to think about personal identity. I happen to think ME is generated by brain. Brain that works so well it can generate mind despite all of those changes in atoms meticulously described by Yudkowsky.

[-][anonymous]1y 13

This "explanation" leaves lingering doubt. It doesn't dissolve all the questions that I have about personal identity. Ok, I'm a factor in a subspace of an amplitude distribution: I get that and I'm okay with that. But there are still unresolved issues of anticipation.

Let's say I record in sufficient fidelity the amplitude distribution factor which represents "me" at this point in time. Then after I am dead some machine is used to recreate this amplitude distribution to sufficient fidelity as to re-create me, as I exist now. That person will come into being with all my memories and with a subjective feeling of actually being me. Furthermore, there is nothing about this "new instance of me" which experimentally differentiates it from the "original me" which is typing these words. (This is the quantum replicator/teleport thought experiment.)

So far, I'm onboard.

Now the quantum realist typified by Eliezer would argue that there is no difference between "new instance of me" and "original me," and I'm stupid for thinking that there is. Furthermore, since personal identity is thus shown to be a phantom of our mind's inner workings, the "new instance of me" objectively is me. I've thus defe

... (read more)

I agree that this is a major unsolved problem. I started thinking about this problem more than 20 years ago which eventually led to UDT (in part as an attempt to sidestep it). At one point I thought maybe we can just give up anticipation and switch to using UDT which doesn't depend on a notion of anticipation, but I currently think that some of our values are likely expressed in terms of anticipation so we probably still have to solve the problem (or a version of it) before we can translate them into a UDT utility function.

1MichaelStJules6moI think this gets at psychological connectedness/continuity. There's a large gap between scanning and the creation of the copy, but actually, maybe there's a gap between your conscious states, too? Connectedness/continuity seems to be an illusion, and the copy could also be under the same illusion. I think you could think of yourself as continuing 100% in all of them (at the time of copying), not some fractional amount. Identity is not transitive or unique in this way; it's closer to something like inheritance/descendance. Your hypothetical biological children would each inherit about half of your genes, no matter how many there are. Your identity descendants could each inherit 100% of your identity, even if they aren't identical to each other.

Can't we distinguish between particles through their relationships with other objects or "themselves", including causal relationships? For example, the electrons in my body now have different (and stronger) causal effects on electrons in my body later than on electrons in your body, and by this we can distinguish them.

And can't we trace paths in spacetime for identity? Not particle-like paths, but by just relying on causality and the continuity of the wavefunction over spacetime? This could give you something like four-dimensionalism, w... (read more)

1Korz6moI think the meaning behind 'identical particles' is very hard to pin down without directly using mathematical definitions*. The analogy with (secretly numbered) billiard balls gives a strong intuition for non-identical particles. There are also intuitive examples that behave more like identical particles: For example, the intuition for symbols nicely matches identical symbol/particle behaviour: If I represent a Helium atom with the symbol "H" and no atom with "_", the balloons interior might be described by "H__H_H____H__H_____H_______H_H__HH____H". Here, it would still make sense to think 'the Helium atom at this position', but thinking 'what if I wrote "the fifth H" at the position of "the third H" and vice versa?' is not meaningful in the same way that the word "identical" remains "identical" even if I claim that I exchanged the two "i". I think this way of distinguishing particles makes sense, but does not rely on 'identity' in the sense of identical particles – your example could be realized both with identical and non-identical particles, as 'identifying' a particle by its state remains valid in both cases. A different, but consistent definition for individual particle-identity might be possible. But, as the experimental predictions** from identical particles are well-confirmed, it would still have to treat the way that two electrons have different identity in a different way than the different identity between an electron and, say, a photon. I do not see how one could get the qm-predictions without also using the identical-particle maths. *) One (simplified) way to write it for 2 particles would be: * For two non-identical particles the wave function is defined over the space of ordered tuples of positions, e.g. (r_1, r_2). Here it makes sense to think 'what happens if I exchanged the two particles?' as (r_2,r_1) is generally not (r_1,_2) and 'exchange particles' is a meaningful term. * For identical particles instead, the wave funct