Identity Isn't In Specific Atoms

by Eliezer Yudkowsky6 min read19th Apr 200874 comments


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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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