Quantum Mechanics and Personal Identity

post by Eliezer Yudkowsky (Eliezer_Yudkowsky) · 2008-06-12T07:13:49.000Z · score: 5 (6 votes) · LW · GW · Legacy · 29 comments

This is one of several shortened indices into the Quantum Physics Sequence.

Suppose that someone built an exact duplicate of you on Mars, quark by quark - to the maximum level of resolution that quantum physics permits, which is considerably higher resolution than ordinary thermal uncertainty.  Would the duplicate be really you, or just a copy?

It may seem unlikely a priori that physics, or any experimental science, could have something to say about this issue.

But it's amazing, the things that science can tell you.

In this case, it turns out, science can rule out a notion of personal identity that depends on your being composed of the same atoms - because modern physics has taken the concept of "same atom" and thrown it out the window.  There are no tiny billiard balls with individual identities.  It's experimentally ruled out.

"Huh?  What do you mean, physics has gotten rid of the concept of 'same atom'?"

No one can be told this, alas, because it involves replacing the concept of little billiard balls with a different kind of math.  If you read through the introduction that follows to basic quantum mechanics, you will be able to see that the naive concept of personal identity - the notion that you are made up of tiny pieces with individual identities that persist through time, and that your identity follows the "same" tiny pieces - is physical nonsense.  The universe just doesn't work in a way which would let that idea be meaningful.

There are more abstract and philosophical arguments that you could use to rule out atom-following theories of personal identity.  But in our case, it so happens that we live in a universe where the issue is flatly settled by standard physics.  It's like proposing that personal identity follows phlogiston.  You could argue against it on philosophical grounds - but we happen to live in a universe where "phlogiston" itself is just a mistaken theory to be discarded, which settles the issue much more abruptly.

And no, this does not rely on a woo-woo mysterian interpretation of quantum mechanics.  The other purpose of this series of posts, was to demystify quantum mechanics and reveal it as non-mysterious.  It just happens to be a fact that once you get to the non-mysterious version of quantum mechanics, you find that the reason why physics once looked mysterious, has to do with reality being made up of different stuff than little billiard balls.  Complex amplitudes in configuration spaces, to be exact, though here I jump ahead of myself.

If you read all the way to the end, you will, I hope, gain an entirely new perspective on where your "identity" is located... once the little billiard balls are ruled out.

You will even be able to see, I hope, that if your brain were non-destructively frozen (e.g. by vitrification in liquid nitrogen); and a computer model of the synapses, neural states, and other brain behaviors were constructed a hundred years later; then it would preserve exactly everything about you that was preserved by going to sleep one night and waking up the next morning.

Mind you, my audacious claim is not that uploading preserves identity - this audacious claim has been made many times before.  I am claiming that once you grasp modern physics, you can actually see this as obvious, even if it would not be obvious to someone thinking in terms of Newtonian billiard balls in classical physics.  This is much more audacious, and I am well aware of how unlikely that sounds; but if you read all the way to the end, it is fully supported.

29 comments

Comments sorted by oldest first, as this post is from before comment nesting was available (around 2009-02-27).

comment by Christopher_Gateley · 2008-06-12T09:30:39.000Z · score: -2 (2 votes) · LW(p) · GW(p)

What's the point of these duplicate posts?

comment by pure-awesome · 2012-07-19T22:37:12.887Z · score: 0 (2 votes) · LW(p) · GW(p)

Oops, interference.

comment by Christopher_Gateley · 2008-06-12T09:31:02.000Z · score: -1 (3 votes) · LW(p) · GW(p)

What's the point of these duplicate posts?

comment by Dmitriy_Kropivnitskiy · 2008-06-12T15:41:44.000Z · score: 2 (2 votes) · LW(p) · GW(p)

What's the point of these duplicate posts?

comment by Z._M._Davis · 2008-06-12T16:10:58.000Z · score: 1 (1 votes) · LW(p) · GW(p)

"What's the point of these duplicate posts?"

As far as Eliezer's apparently redundant posts go: the QM indicies aren't exact duplicates of each other: they have different introductions, include or exclude some posts, have different posts bolded or not, &c. One reason for the multiple indicies seems to be to have somewhere to link to when making some seemingly percarious claim about QM elsewhere on the internet--cf. especially the intoduction to the "nonmysterious" index.

As far as the duplicate comments above go: it looks like Christopher double-posted by mistake, and Dmitriy is making a joke.

comment by Joseph_Hertzlinger · 2008-06-12T16:48:57.000Z · score: 1 (1 votes) · LW(p) · GW(p)

On the other hand, the "no-cloning" theorem might imply that exact duplicates cannot be created.

comment by Silas · 2008-06-12T17:46:38.000Z · score: 2 (2 votes) · LW(p) · GW(p)

Whoa whoa whoa, I'm not disputing any of your physics. I'm just questioning how certain you can be that you'll never find a difference between Christopher Gateley's posts! ;-)

comment by MichaelAnissimov · 2008-06-13T02:40:36.000Z · score: 1 (1 votes) · LW(p) · GW(p)

I strongly advise against Lulu, btw. You can find a real publisher, even if it's a smallish one.

Unfortunately, it might be difficult to find a publisher that accepts that the book is already online in blog form, or that allows you to release it in e-book form.

It might be necessary to get 500 or so people to sign some sort of petition to convince the publisher that your book is really worth publishing, under those circumstances.

comment by mitchell_porter2 · 2008-06-13T03:47:58.000Z · score: 1 (1 votes) · LW(p) · GW(p)

Blogs have been turned into books before, e.g. Iraqi bloggers Salam Pax and Riverbend.

comment by Christopher_Gateley · 2008-06-13T10:32:29.000Z · score: 0 (0 votes) · LW(p) · GW(p)

Yeah, sorry about the double posting. I should no better than to use the browser 'back' button after using a form.

It is rather ironic, though.

comment by TimFreeman · 2011-05-16T17:33:52.532Z · score: 0 (0 votes) · LW(p) · GW(p)

In this case, it turns out, science can rule out a notion of personal identity that depends on your being composed of the same atoms - because modern physics has taken the concept of "same atom" and thrown it out the window. There are no tiny billiard balls with individual identities. It's experimentally ruled out.

Science does not rule out a notion of personal identity that requires the location of an individual to be a continuous function, which would imply that the copy of me on Mars isn't me, assuming I started on Earth.

My point isn't that I advocate such a notion of personal identity. My point is that the boundaries of the "self" are a choice that can't be justified rationally.

comment by nshepperd · 2011-05-17T01:37:31.867Z · score: 0 (0 votes) · LW(p) · GW(p)

A choice? Not quite... You don't get to choose whether you experience life or death when you teleport by copying-and-destruction.

comment by TimFreeman · 2011-05-17T02:32:57.498Z · score: 3 (3 votes) · LW(p) · GW(p)

A choice? Not quite... You don't get to choose whether you experience life or death when you teleport by copying-and-destruction.

Something happens when you teleport by copying-and-destruction. We probably agree about what actually happens. Whether you call it life or death is a choice, just as any other decision to use one word or another to describe a situation is a choice. If we take the definitions of "life" and "death" as fixed, you don't get to choose whether copy-and-destruction fits the definition or not.

It's best not to confuse choosing what happens with choosing what to call it.

The boundary of the self is in the second category.

comment by nshepperd · 2011-05-17T02:57:35.936Z · score: 1 (1 votes) · LW(p) · GW(p)

It doesn't seem to you that the subjective experience of life or death (continuing to have subjective experience or not) is something fixed by the physical process that has nothing to do with definitions? Sure, you can "define 'self' however you like", but then it might not capture what you care about, which for most people is continuation of subjective experience.

comment by [deleted] · 2011-05-17T03:17:33.653Z · score: 0 (0 votes) · LW(p) · GW(p)

Sure, you can "define 'self' however you like", but then it might not capture what you care about, which for most people is continuation of subjective experience.

The claim that you can define it is actually a statement about the nature of the supposed continuation of subjective existence. That is not being ignored. It is precisely what is being commented on.

comment by [deleted] · 2013-09-27T16:25:11.604Z · score: -1 (1 votes) · LW(p) · GW(p)

Whether you call it life or death is a choice, just as any other decision to use one word or another to describe a situation is a choice.

OTOH, some such choices are worse than others.

comment by TimFreeman · 2013-10-21T15:44:03.887Z · score: 1 (1 votes) · LW(p) · GW(p)

OTOH, some such choices are worse than others.

If you have an argument, please make it. Pointing off to a page with a laundry list of 37 things isn't an argument.

One way to find useful concepts is to use evolutionary arguments. Imagine a world in which it is useful and possible to commute back and forth to Mars by copy-and-destroy. Some people do it and endure arguments about whether they are still the "same" person when they got back, some people don't do it because of philosophical reservations about being the "same" person. Since we hypothesized that visiting Mars this way is useful, the ones without the philosophical reservation will be better off, in the sense that if visiting Mars is useful enough they will be able to out-compete the people who won't visit Mars that way.

So if you want to say that going places by copy-and-destroy is a bad thing for the person taking the trip, you should be able to describe the important way in which this hypothetical world where copy-and-destroy is useful is different from our own. I can't do that, and I would be very interested if you can.

Freezing followed by destructive upload seems moderately likely to be useful in the next few decades, so this hypothetical situation with commuting to Mars is not irrelevant.

comment by Jiro · 2013-10-21T18:15:17.089Z · score: 0 (4 votes) · LW(p) · GW(p)

This reasoning can be used to justify almost any form of "what you don't know won't hurt you". For instance, a world where people cheated on their spouse but it was never discovered would function, from the point of view of everyone, as well as or better than the similar world where they remained faithful.

Most of us think the former world is bad and, if pressed, would explain it by saying that blissful ignorance is not a good thing. Even though "my spouse cheats on me but I don't know it" and "my spouse doesn't cheat on me" are indistinguishable, I have been harmed in the former situation.

comment by shminux · 2013-10-21T18:40:06.303Z · score: 1 (1 votes) · LW(p) · GW(p)

How have you been harmed, exactly?

comment by TimFreeman · 2013-10-25T05:50:46.383Z · score: 1 (1 votes) · LW(p) · GW(p)

This reasoning can be used to justify almost any form of "what you don't know won't hurt you". For instance, a world where people cheated on their spouse but it was never discovered would function, from the point of view of everyone, as well as or better than the similar world where they remained faithful.

Your example is too vague for me to want to talk about. Does this world have children that are conceived by sex, children that are expensive to raise, and property rights? Does it have sexually transmitted diseases? Does it have paternity tests? Does it have perfect contraception? You stipulated that affairs are never discovered, so liberal use of paternity tests imply no children from the affairs.

I'm also leery of the example because I'm not sure it's relevant. If you turn off the children, in some scenarios you turn off the evolution so my idea of looking at evolution to decide what concepts are useful doesn't work. If you leave the children in the story, then for some values of the other unknowns jealousy is part of the evolutionarily stable strategy, so your example maybe doesn't work.

Can you argue your point without relying so much on the example? "Most of us think X is bad" is perhaps true for the person-copying scheme and if that's the entire content of your argument then we can't address the question of whether most of us should think X is bad.

comment by Jiro · 2013-10-25T14:51:45.486Z · score: 1 (1 votes) · LW(p) · GW(p)

"Most of us think X is bad" is perhaps true for the person-copying scheme

I'm not saying that most people think this scheme is bad, I'm saying that most people don't have the definition of harm that you do. Your idea that all harm must be knowing is not one commonly shared.

And the example has nothing to do with paternity. Most people would think that a world where people are cheated on but it is not discovered is one where the other partner is being harmed, simply because cheating on someone harms them and harm does not have to be knowing in order to be harm. Or, as I summarized, most people don't think blissful ignorance is a good thing.

comment by TimFreeman · 2013-10-26T05:52:47.433Z · score: 0 (0 votes) · LW(p) · GW(p)

Nothing I have said in this conversation presupposed ignorance, blissful or otherwise.

I give up, feel free to disagree with what you imagine I said.

Check out Argumentum ad Populum. With all the references to "most people", you seem to be committing that fallacy so often that I am unable to identify anything else in what you say.

comment by Jiro · 2013-10-26T18:14:03.890Z · score: -2 (4 votes) · LW(p) · GW(p)

The argument you made was that copy-and-destroy is not bad because a world where that is done is not worse than our own. In turn, your belief that it is not worse than our own is, as far as I can tell, based on the belief that you can compare that world to our own by comparing whether it is good for the people who remain alive, and ignoring whether it is good for the people who are killed. This implies that the fact that the person is killed doesn't count towards making the world worse because being dead, he can't know that he has been harmed, and because the other people don't feel the loss they would feel that goes with a normal death. This amounts to blissful ignorance (although I suppose the dead person can be more accurately described as having 'uncaring ignorance', since dead people aren't very blissful).

Check out Argumentum ad Populum. With all the references to "most people", you seem to be committing that fallacy so often that I am unable to identify anything else in what you say.

Pointing out that your definition of something, like harm, is shared by few people is not argumentum ad populum, it's pointing out that you are trying to sound like you're talking about something people care about but you're really not.

comment by TimFreeman · 2013-10-27T19:39:51.998Z · score: -1 (3 votes) · LW(p) · GW(p)

Well, I suppose it's an improvement that you've identified what you're arguing against.

Unfortunately the statements you disagree with don't much resemble what I said. Specifically:

The argument you made was that copy-and-destroy is not bad because a world where that is done is not worse than our own.

I did not compare one world to another.

Pointing out that your definition of something, like harm, is shared by few people is not argumentum ad populum, it's pointing out that you are trying to sound like you're talking about something people care about but you're really not.

I did not define "harm".

The disconnect between what I said and what you heard is big enough that saying more doesn't seem likely to make things better.

The intent to make a website for the purpose of fostering rational conversation is good, and this one is the best I know, but it's still so cringe-inducing that I ignore it for months at a time. This dialogue was typical. There has to be a better way but I don't know what it is.

comment by Jiro · 2013-10-28T00:45:52.807Z · score: 1 (1 votes) · LW(p) · GW(p)

I did not compare one world to another.

Um.

you should be able to describe the important way in which this hypothetical world where copy-and-destroy is useful is different from our own.

(I suppose you could quibble that you didn't say it was not worse, but "not different" is a subset of "not worse"; you certainly did compare one world to another.)

comment by EphemeralNight · 2013-03-31T23:40:25.342Z · score: 0 (0 votes) · LW(p) · GW(p)

Science does not rule out a notion of personal identity that requires the location of an individual to be a continuous function, which would imply that the copy of me on Mars isn't me, assuming I started on Earth.

You know, the first time I read this sequence post, I thought something similar. But then something clicked.

Yes, if you create a duplicate of me on mars, and then disintegrate the me that's still on earth at some point afterward, that's murder. But I realized that asking if that was killing me was a Wrong Question.

When the process that is me is duplicated, neither copy takes precedence. Both are me in every sense. The me that walks into the transporter has an equal chance of experiencing me-on-earth and me-on-mars after the machine does its thing.

This is counterintuitive, since it seems like the me-on-earth is the original me, but if there's no such thing as "the same atoms" then the very idea that one of the identical mes is the original is physical nonsense. There being no "same atoms" explicitly disallows the me-process that continues in the earth-me-brain to be any more me than the me-process that continues in the mars-me-brain.

This doesn't make it okay to kill earth-me after I step off the transporter pad. Until we know more about how consciousness works, I would suggest that allowing even one neuron to fire post-replication would make destroying earth-me murder. Better to err on the side of caution about something like that.

Fun fact, this applies equally to Uploading as it does to transporter replication. It was actually uploading that I was pondering when this clicked for me.

comment by BobTheBob · 2011-05-22T17:35:30.755Z · score: 0 (0 votes) · LW(p) · GW(p)

''test''