Identity Isn't In Specific Atoms
post by Eliezer Yudkowsky (Eliezer_Yudkowsky) · 2008-04-19T04:55:50.000Z · LW · GW · Legacy · 73 commentsContents
73 comments
Continuation of: No Individual Particles
Followup to: The 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"
73 comments
Comments sorted by oldest first, as this post is from before comment nesting was available (around 2009-02-27).
comment by Wiseman · 2008-04-19T05:53:01.000Z · LW(p) · GW(p)
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?
comment by Eliezer Yudkowsky (Eliezer_Yudkowsky) · 2008-04-19T07:02:41.000Z · LW(p) · GW(p)
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.
comment by Will_Pearson · 2008-04-19T07:08:05.000Z · LW(p) · GW(p)
"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.
comment by mitchell_porter2 · 2008-04-19T08:00:36.000Z · LW(p) · GW(p)
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 consider some of what we've been told. Suppose a physical system starts in situation A, and ends in situation B. The probability of this happening can be found by summing the amplitudes for a number of "histories" which began with A and end with B. OK; but what do we think actually happened in between? If those amplitudes were probabilities, it would be reasonable to say that just one of those histories actually happened. Not so in quantum mechanics; in quantum mechanics, sometimes things never happen because all the ways that they can happen cancel each other out (the amplitudes sum to zero). That is nonsense, it is an obvious indication that we are conceptualizing things incorrectly.
In any case, Eliezer seems to be saying that between A and B, what happens is everything and nothing. We have amplitude flows in configuration space. Configurations themselves do not change, just the amplitudes associated with them. Well, in real life something definitely changed - A became B. The picture needs more detail, to expain what that involves. Eliezer clearly favors the many-worlds explanation, but I can't critique it unless he shows me the details. For now, we just have underspecified nonsense.
It also turns out that the point of this digression was to make an argument about personal identity and its continuity over time: whatever the reason is that I, now, am to be considered the same entity as I, five minutes ago, it can't have to do with persistence of my physical parts, because my physical parts don't "have identity". So, if I focus on the proton in a particular hydrogen atom in a particular nucleotide in a particular cell in my body, I don't have any grounds for thinking that the proton that's there now is the same proton that was there a millisecond ago; at least, it's not that proton to any greater degree than it is also any other proton in the universe.
This is clealy an odd view. There are at least two possible reactions to it. One is to say, well, it's odd, but it's what Authority tells me that Experiment is saying, so I'd better believe it. Or, one might want to look a little closer at the details, and see if the peculiar interpretation holds up. In this case, I think that proceeding to the perspective of field configurations might be called for. I'm not at all sure that this stuff about indistinguishability is anything more than an artefact of taking particle configurations to be fundamental, rather than field configurations. (And that, incidentally, is another aspect of the quantum problem that this exposition hasn't mentioned, the question of which "basis" to use.)
Just some preliminary thoughts.
comment by Eliezer Yudkowsky (Eliezer_Yudkowsky) · 2008-04-19T08:06:47.000Z · LW(p) · GW(p)
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.
comment by mitchell_porter2 · 2008-04-19T08:30:09.000Z · LW(p) · GW(p)
I'll sit down and let the second act begin, then. :-)
comment by Tom_McCabe2 · 2008-04-19T14:51:35.000Z · LW(p) · GW(p)
"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 charge. Why does the universe so carefully conserve these particular bundles of amplitude, with only one exception that I am aware of (annihilation by positrons), while other bundles of amplitude never exist at all (eg., a particle with 360 keV rest mass, or a particle with 7/2 charge).
comment by David_D · 2008-04-19T15:25:06.000Z · LW(p) · GW(p)
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 that light is like a bunch of soldiers that "want" to stay in line, so when they hit a patch of mud (i.e. when they have to move slower) they change direction. Another explanation I have been given (which is a bit closer to the QED one) is that light "wants" to get from point A to point B as fast as possible, so it "chooses" the path through the glass (or whatever) that will accomplish this.
The QED explanation (i.e. all of the fastest paths tend to have similar phases so they do not cancel each other out like the slower ones do) was much more satisfying.
FWIW, learning about amplitudes in terms of complex numbers before I started reading the book really helped me grok the arrows that Feynman uses. Otherwise, it would probably take my brain a few steps to keep the "amplitude arrows" and the "possible path of the photon arrows" separate.
Anyway, if anybody reading these posts are as lost as me, I would strongly recommend the QED book.
comment by Wiseman · 2008-04-19T15:26:42.000Z · LW(p) · GW(p)
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?
comment by anonymous7 · 2008-04-19T17:09:56.000Z · LW(p) · GW(p)
If you believe that p-zombies are logically impossible, you're claiming that when one does an atom simulation, and those atoms happen to form a human brain, then it creates a pathway to the consciousness-stuff, and not only that, but that consciousness-stuff has a precise, causal effect on your atom simulation. And not only that, but the effect amazingly changes the thought process using a protocol that evolution has just happened to choose! Pretty remarkable claim to me.
comment by Aaron_Boyden · 2008-04-19T17:26:56.000Z · LW(p) · GW(p)
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.
comment by Unknown · 2008-04-19T18:52:23.000Z · LW(p) · GW(p)
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 happened to you, the reader, in the middle of this sentence, with your vat experiences beginning with the words "the reader."
The fact that there is absolutely no way to prove or disprove this scenario does not make it logically impossible. It just makes it highly improbable. Likewise, the soul swap world, and the zombie world, are highly improbable. This is no reason at all to call them logically impossible.
This whole thing is simply another case of Eliezer's overconfidence: if there is something that one should be somewhat confident of, then he is extremely confident of it. If there is something that one should be extremely confident about, such as that there are no zombies in the world, then he is infinitely certain about it: he thinks it is logically impossible.
comment by Richard4 · 2008-04-19T20:23:47.000Z · LW(p) · GW(p)
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.)
comment by Caledonian2 · 2008-04-19T20:47:50.000Z · LW(p) · GW(p)
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.
comment by Toby_Ord2 · 2008-04-19T21:04:44.000Z · LW(p) · GW(p)
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.
comment by Z._M._Davis · 2008-04-19T23:56:35.000Z · LW(p) · GW(p)
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.
comment by Hopefully_Anonymous · 2008-04-20T01:44:10.000Z · LW(p) · GW(p)
"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 black hole forming in another universe, etc.
Here I'm defining 'consciousness-stuff' in what I think is the most reasonable and useful way for this discussion, that there may be something to subjective consciousness more than whatever can currently fool the best human observers in 2008 into thinking it's subjectively conscious. This is probably a higher bar than 40th percentile ability level human observers of 2008 BCE, but perhaps a significantly lower bar than the best human observers of 2038. If the best human observers of 2038 have singificantly improved knowledge and technology, they might be able to make more nuanced discernments between what is or is not likely subjective conscious than the best humans can in 2008. If so, in all practical respects, I think that those differences they'll be able to discern can be called "cosciousness-stuff" of which we're current unaware. Here I'm not specifically referring to a tagged electron, or a tagged factored subspace, but rather, when Eliezer writes:
"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."
I'm referring to consciousness-stuff as the minimal distinguishable elements of reality required for the maintainence of the subjective conscious experience which Eliezer implies in the above quote could be ended "if an anvil falls on your head".
In my opinion, this is a more interesting place to bring the discussion, than to look for easy dragons to slay such as (scare quotes) "These people think individual electrons are discrete entities. I can show that the best science disproves that and thus end any concern that post-cryonic reanimation or post-uploading I won't have an experience of being 'alive' or 'conscious'.
comment by Bob5 · 2008-04-21T20:06:58.000Z · LW(p) · GW(p)
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?
Replies from: ramana-kumar↑ comment by Ramana Kumar (ramana-kumar) · 2009-10-31T21:52:34.198Z · LW(p) · GW(p)
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?
No, 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".
comment by Nick_Tarleton · 2008-04-21T20:25:02.000Z · LW(p) · GW(p)
And I expect the Personal Identity Wars started well before then.
comment by Richard4 · 2008-04-22T00:08:54.000Z · LW(p) · GW(p)
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.
comment by Caledonian2 · 2008-04-22T00:43:35.000Z · LW(p) · GW(p)
No, Richard. Just... no.
How can you have missed the point that badly?
comment by lucidfox · 2010-12-14T10:36:53.372Z · LW(p) · GW(p)
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 is no such thing as a "me" that can jump between brains. If "jumping between brains" means something, then it could mean two things:
For me to subjectively experience "waking up as Britney Spears", I'll need to retain the memories of being the current me up to that point. That would mean that Britney Spears' brain would need to be physically altered to inscribe my memories, rather than hers, which contradicts our premise that no physical attributes are being altered.
If "I" end up in Britney Spears' body but lose "my" original memories, and likewise "Britney Spears" becomes me, then it no longer makes any sense to speak about preservation of personal identity, any more than it makes sense to ask "If we simultaneously yanked every plank composing the Ship of Theseus out of its space, and warped different planks into their space to make a ship of a completely different shape, would it still be the same ship"? If "being the same ship" or "being the same person" means anything at all, then it is a different ship, and likewise, the hypothetical "me in Britney Spears' body but with Britney Spears' memories instead of mine" is exactly the same person as Britney Spears. There is no incorporeal identity tag that we can attach to minds, any more than we can do so for electrons.
↑ comment by shokwave · 2010-12-14T10:47:43.616Z · LW(p) · GW(p)
If "I" end up in Britney Spears' body but lose "my" original memories, and likewise "Britney Spears" becomes me, then it no longer makes any sense to speak about preservation of personal identity
That is the intended conclusion from the Soul Swap World thought-experiment.
comment by PhilosophyFTW · 2011-05-28T02:11:29.704Z · LW(p) · GW(p)
Eliezer,
In another post you write: "Quantum mechanics has been around for billions of years before the Sun coalesced from interstellar hydrogen. Quantum mechanics was here before you were, and if you have a problem with that, you are the one who needs to change. QM sure won’t."
Where did you get this notion from? QM is inconsistent with GR. I could just as easily (and just as unreasonably) assert that GR has been around for billions of years... The problem with that assertion would be the same problem with your assertion. There is no evidence for it.
What makes you a QM-pusher instead of a GR-pusher? It's not evidence, and you can't push both. Is this your favorite flavor of the times? As another poster in this thread has noted, the degree of confidence you have in some of the statements you make is way, way off base.
Here's one more example of your radically misplaced confidence. You write: "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."
I'm glad it made you happy to say it. But you have no good argument for it. Nor do I think that on your views you could possibly have a reason to believe it.
You also write: "We live in a quantum universe where the notion of "same hydrogen atom vs. different hydrogen atom" is physical nonsense."
Let's suppose your misplaced faith in QM is rational (it isn't, but let's suppose it is). And let's suppose that the notion you describe is "physical nonsense". (Maybe it is. Maybe it isn't.) It doesn't follow that the notion you describe is nonsense unless you assume that something is nonsense if it is physical nonsense. And here, of course, you are hardly entitled to that assumption. It sounds just like the indefensible verificationist swill spewed by the rabid and wholly irrational logical positivists.
You're worshipping at the altar of science and you're picking and choosing the science you think will help you best defend your funny views, and then you're baldly asserting that this science constitutes a true description of reality EVEN WHEN IT CONTRADICTS other scientific theories (such as GR) that have just as good scientific credentials.
Unless you have some sexy response to this post, I will assume that you would get laughed out of a philosophy of science department.
Replies from: Nornagest, Dreaded_Anomaly, endoself↑ comment by Nornagest · 2011-05-28T02:31:03.457Z · LW(p) · GW(p)
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 tested QM results, including the weird ones, have to be explainable by the underlying mechanics.
We're not going to discover some result in the future that'll make quantum mechanics -- or general relativity, or any other well-established physical theory -- throw up its hands and disappear. We very likely will discover results that'll explain reality better than they do, but that reality includes everything they predict within the domains where they've been shown to work well. Science is not a race, nor a battle.
↑ comment by Dreaded_Anomaly · 2011-05-28T02:38:47.640Z · LW(p) · GW(p)
Quantum mechanics makes a multitude of predictions which have been experimentally verified. Yes, it's inconsistent with general relativity. Newtonian mechanics is inconsistent with Maxwell's equations, which led to the theory of special relativity. Special relativity contains those other theories, which are inconsistent by themselves. If there's a better theory which can describe both quantum and gravitational phenomena, it will contain quantum mechanics and general relativity. The experimentally confirmed results of quantum mechanics will still be relevant in their domain, just as F = ma is still a useful equation today for objects with velocities much less than the speed of light.
↑ comment by endoself · 2011-05-28T02:51:20.194Z · LW(p) · GW(p)
Quantum mechanics is not inconsistent with general relativity, the standard ways of quantizing a theory fail for general relativity. This is not a surprise; physicists knew that these standard methods were not complete, they just produced theories that worked well enough when applied in other areas. Based on your post, it is somewhat likely that you read popular material about loop quantum gravity. If that theory is consistent, has the right long distance limits, etc., then it is both a quantum mechanical and general relativistic theory.
Even if quantum mechanics is overthrown, whatever replaces it will have to be enough like it that we would not have noticed the difference, which is a very stringent requirement, especially given quantum computing experiments. Quantum mechanics is a very rigid structure, and it is difficult to make something only slightly different.
comment by PhilosophyFTW · 2011-05-28T02:45:48.092Z · LW(p) · GW(p)
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 make quantum mechanics -- or general relativity, or any other well-established physical theory -- throw up its hands and disappear.
If we discover that QM is true, we will give up GR. You can't have both. Sorry mate. You could have something like GR, perhaps, but it wouldn't be GR.
We very likely will discover results that'll explain reality better than they do, but that reality includes everything they predict within the domains where they've been shown to work well. Science is not a race, nor a battle.
If you want to make QM-domain specific, fine. QM is true in whatever domains saying QM is true doesn't result in a contradiction with GR. That's nice and ad-hoc, but you can have fun with that. And it'll render all the arguments from the truth of QM to broader claims about reality utterly moot. So again, fail.
comment by PhilosophyFTW · 2011-05-29T02:06:24.593Z · LW(p) · GW(p)
Quantum mechanics is not inconsistent with general relativity, the standard ways of quantizing a theory fail for general relativity. This is not a surprise; physicists knew that these standard methods were not complete, they just produced theories that worked well enough when applied in other areas. Based on your post, it is somewhat likely that you read popular material about loop quantum gravity. If that theory is consistent, has the right long distance limits, etc., then it is both a quantum mechanical and general relativistic theory.
GR and QM are generally agreed to indeed be inconsistent. There are various attempts to come up with theories of quantum gravity. One of these attempts follows particle based physics: string theory and extensions of string theory. The other attempt is GR based, and includes loop quantum gravity and canonical quantum gravity (along with extensions, such as fixed-foliation quantum gravity).
I'll give you that loop-quantum gravity is "quantum mechnical" and "general realtivistic". But it isn't QM or GR. This isn't a reasonable way of defending your claim that QM and GR are consistent.
And no, I don't read any popular literature. I hope the above helped explain my previous post a bit.
Replies from: endoself, Mitchell_Porter↑ comment by endoself · 2011-05-29T03:13:33.520Z · LW(p) · GW(p)
Why did you not write this as a reply to me?
GR and QM are generally agreed to indeed be inconsistent.
[Citation needed]
I'll give you that loop-quantum gravity is "quantum mechnical" and "general realtivistic". But it isn't QM or GR.
Quantum mechanics is the theory that reality is described by the Schrodinger equation; loop quantum gravity includes the Schrodinger equation. Its proponents claim that it includes the general relativity field equations as a long distance limit; that is what we mean when we say that one theory is a quantization of another, just like quantum and classical electrodynamics.
And no, I don't read any popular literature. I hope the above helped explain my previous post a bit.
95% probability less than 10% of the physics you read is from journals/arXiv.
Replies from: PhilosophyFTW, None↑ comment by PhilosophyFTW · 2011-05-29T06:29:24.743Z · LW(p) · GW(p)
Quantum mechanics is the theory that reality is described by the Schrodinger equation
You are insane.
95% probability less than 10% of the physics you read is from journals/arXiv.
Feel free to make further claims you have no evidence for. Here's an article from arXiv you might find interesting: http://arxiv.org/abs/0809.4144
I'm surprised that you put arXiv in the same class you put whatever it is you mean by journals. Maybe I should take the above article seriously? After all, arXiv makes it available. Get out of town.
Replies from: None, endoself↑ comment by [deleted] · 2011-05-29T06:32:10.432Z · LW(p) · GW(p)
You win two paper-machine points [1]: one for observing the true nature of arXiv, and the other for implicitly deriding those who argue the countability of the reals.
[1] Probably not redeemable for anything you'd want.
EDIT: Don't be too harsh on the mantra "QM says reality is described by Schrodinger". It's the noble lie they tell undergraduates -- or at least, what they told me when I was an undergraduate. In my opinion, it's slightly unfair to expect the average LW'er to have a better-than-undergraduate knowledge of QM.
Replies from: PhilosophyFTW, endoself↑ comment by PhilosophyFTW · 2011-05-29T06:40:51.861Z · LW(p) · GW(p)
Thanks for the points. Yes, ArXiv frequently sucks. And people who argue that the set of real numbers has the same cardinality as the set of natural numbers are morons.. =)
↑ comment by endoself · 2011-05-29T07:34:58.092Z · LW(p) · GW(p)
Don't be too harsh on the mantra "QM says reality is described by Schrodinger". It's the noble lie they tell undergraduates -- or at least, what they told me when I was an undergraduate.
Now I'm interested. In what way are "quantum mechanics" and "vector on a Hilbert space evolving according to Schrodinger's equation" not the same concept?
Replies from: None↑ comment by [deleted] · 2011-05-29T07:47:07.265Z · LW(p) · GW(p)
They are. I guess the mantra I quoted should have been, "It is true that QM describes reality." That's what I assume the grandparent thought you were saying, anyway. It's not worth calling someone insane over a definition.
Replies from: endoself↑ comment by endoself · 2011-05-29T07:30:52.427Z · LW(p) · GW(p)
I never stated that every paper on the arXiv was good.
You have neither confirmed nor denied my actual statement.
QM and GR, if you stick them together, entail everything.
I'm not sure what your point is here. If you stick quantum mechanics and Maxwell's equations together, everything is entailed, but quantum electrodynamics did not give identity back to specific particles. It would be very unlikely for quantum gravity to do that either; certain parts of nature fit perfectly into a very rigid structure and the basic framework of quantum mechanics can be explained but will probably not be eliminated. You can't point to a specific part of a theory and say "the theory is wrong, so that result is wrong"; theories get improved, but they still have to have enough of the same structure to derive the results already tested by experiment.
↑ comment by [deleted] · 2011-05-29T06:37:47.681Z · LW(p) · GW(p)
GR and QM are generally agreed to indeed be inconsistent
[Citation needed]
So I was somewhat surprised that Wikipedia claims that the above is a "popular claim", and goes on to cite some yoga involving the quantum mechanics of gravitons, whatever that means. I'm a mathematician, dammit Jim, not a theoretical physicist.
I think a more accurate version of what the grandparent meant is that one cannot merely take QM and GR, stick them together, and hope to get a coherent theory. One needs something more (for example, the above requires the existence of gravitons), and that's why people go hunting for unified theories.
Replies from: PhilosophyFTW↑ comment by PhilosophyFTW · 2011-05-29T07:05:09.293Z · LW(p) · GW(p)
Relying upon Wikipedia is not advised here. QM and GR, if you stick them together, entail everything. (On the assumption that from a contradiction one can derive anything. Paraconsistent logical systems deny this assumption.) For some proposition, sentence, statement or utterance that P, QM entails P. GR entails not-P. Absent abandoning classical logic (and moving to something like paraconsistent logic), GR and QM are inconsistent.
Let's assume that a theory is false if the theory entails P and not-P (that is, let's ignore paraconsistent logical sytstems). Then sticking GR and QM together entails P and not-P. Any theory that entails both P and not-P is false. So sticking them together fails.
Almost all physicists are happy with the above claims, and so there is an ongoing search for theories that preserve what's supposedly right about QM with what's supposedly right about GR. Enter theories of quantum gravity. These theories might be in some respects "quantum mechanical". That is, they preserve some aspects of QM. These theories aren't QM or GR, however. They're attempts to preserve what's right (let's suppose) about QM and make that compatible with what's right (let's suppose) about GR.
We're utterly in the dark about which such theories might be true. Sadly, that's the state of the game. If you appeal to QM in defense of some interesting claim, you are failing to appeal to a theory you ought, as an intelligent and well-educated person, place a high degree of credence in. Here our favorite blogger is is screwing up.
Replies from: None↑ comment by [deleted] · 2011-05-29T07:17:51.274Z · LW(p) · GW(p)
Relying upon Wikipedia is not advised here. QM and GR, if you stick them together, entail everything.
I'm confused how you got this out of the above -- I didn't mean to imply that QM+GR was consistent. They need fixing, and the article supports this viewpoint. Grandparent asked for citations; the relevant article has several. I didn't see the earlier comments between you and endoself, because they're not in this thread, but in another, for some reason. For what it's worth, I think you're misinterpreting statements intended for poetic effect.
So while endoself is wrong when he claims QM isn't inconsistent with GR, you're equally wrong for believing EY supports QM over GR, when in fact it's incredibly likely (based on everything we know about EY's stance on updating) that for now EY supports QM when it talks about small things and GR when it talks about big things, and that if some better theory would come along that explained the evidence better, EY would update to follow that.
Of course, I can't speak for him, but I claim the above is a more reasonable interpretation of the state of affairs.
EDIT: So there's a simpler litmus test to apply here -- has EY directly said anything about GR? If so, what evidence is leading you to believe he denies it?
Replies from: wedrifid, endoself↑ comment by wedrifid · 2011-05-29T08:36:51.061Z · LW(p) · GW(p)
Grandparent asked for citations; the relevant article has several.
The source of your confusion is the meaning of the phrase 'Citation Needed'. It seldom has anything to do with wanting citations. Actually giving them to him is like answering a (bad) rhetorical question with a literal answer that effectively refutes the rhetorical point of asking it.
Replies from: None↑ comment by [deleted] · 2011-05-29T08:40:21.309Z · LW(p) · GW(p)
What else does it mean?
Replies from: wedrifid↑ comment by wedrifid · 2011-05-29T10:42:47.008Z · LW(p) · GW(p)
What else does it mean?
- "My beliefs are the default and privileged. You have the burden of justifying your beliefs to me."
- "Get back in your place! Who do you think you are?"
- "Your momma is inconsistent with General Relativity! But I'm saying it using an intellectual meme rather than the low brow meme."
Basically, if someone told me 'Citation Needed!' in the same conversation that they out of the blue told me I was insane then I would expect them to do whatever they could to find a way to sneer at or dismiss the citations I proceed to give them. I would expect them to feel like their grasp for dominance backfired and try to dig themselves out of what feels like a hole.
This isn't to say that 'citation needed' is never used literally or never appropriate. But I usually find that anyone who is actually interested in whether there are citations available tends to use different language in their reply.
Replies from: None↑ comment by [deleted] · 2011-05-29T11:07:15.955Z · LW(p) · GW(p)
Ah, I see.
Basically, if someone told me 'Citation Needed!' in the same conversation that they out of the blue told me I was insane
Those two things weren't done by the same person. endoself used [Citation Needed]; PhilosophyFTW called him insane in the followup, for a different reason.
Replies from: wedrifid↑ comment by wedrifid · 2011-05-29T11:17:41.163Z · LW(p) · GW(p)
Those two things weren't done by the same person. endoself used [Citation Needed]; PhilosophyFTW called him insane in the followup, for a different reason.
Ahh. That changes the likely meaning somewhat (greater weight to the first bullet point, less to the last one).
↑ comment by endoself · 2011-05-29T08:50:30.069Z · LW(p) · GW(p)
endoself is wrong when he claims QM isn't inconsistent with GR
I interpreted "QM is inconsistent with GR" as stating that GR cannot be quantized. This is usually what is mentioned in such discussions, as GR is much harder, maybe even impossible, to quantize as compared to other theories. There are very large advantages to only using the word 'consistent' in its precise mathematical definition, so I will do that from now on.
Replies from: PhilosophyFTW↑ comment by PhilosophyFTW · 2011-06-05T01:30:58.178Z · LW(p) · GW(p)
In the simplest of terms, theory T is inconsistent with theory T if the conjunction of T and T entails everything in a classical logical system.
Since QM is inconsistent with GR, and since not every proposition is true, either QM or GR is, strictly speaking, false. Perhaps both are false.
The OP, Eliezer, must think that GR is false, since he's gone out and endorsed QM. This is not a good position to be in. More charitably, the OP has tried to endorse everything in QM that he thinks he needs for his argument, and he's asserted that all that requisite material will be retained in any future scientific theory.
The OP is then pleading that whatever physical theory turns out to be true will be sufficiently like QM that he's entitled to rely on QM in the ways he is. Call this quantum mechanical optimism or hopeful thinking. I don't see the argument here. Sorry.
He can conditionalize his claims. He can say things like, "If QM is true, then..." or "If the true physical theory preserves what there is in QM that I need for my argument, then..." But this isn't what he's doing.
And finally, even if the OP were to conditionalize, he'll still in hot water. Maybe the OP means by "physical nonsense" something like: contradicts claims that follow from QM. But he doesn't mean this. He's trotting in his own favorite little philosophical theory, without defense while pretending to rely upon good science (though he's in fact relying on very probably false science, since QM and GR can't both be true). This is evident when he writes: "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." Let's suppose that there are such particle-tags. Call them properties. And let's grant that they don't affect particle motion. Let's even grant that they're epiphenomenal. See how charitable I'm being to the OP?
Now obviously, it doesn't follow from QM that these epiphenomenal particle tags don't exist. The OP can beat his brain against the wall for the rest of his life and never manage to show it does so follow. Eliezer believes these particle tags don't exist, which is why he calls them imaginary, but he has not managed to produce one wit of evidence for that claim. I take it the OP would probably rely upon the following assumption: Nothing epiphenomenal exists. That's an interesting philosophical claim, and the OP can't pretend to defend it by giving us more very probably false physical theories. Nor does it follow from any physical theory the OP has mentioned so far.
When reading the OP, I am reminded of William Lane Craig's attempts to use The Big Bang to defend a central claim he needs for his Cosmological Argument: the universe had a beginning. Craig is in hot water here, for it does not follow from any of our best scientific theories, including all Big Bang Theories, that the universe had a beginning. Craig is using scientific dressing to peddle shoddy arguments that those unfamiliar with the science will be rhetorically overwhelmed by, and I don't see the difference between what he does and what the OP is doing.
Replies from: nshepperd↑ comment by nshepperd · 2011-06-05T05:20:36.142Z · LW(p) · GW(p)
Well, yes. Two theories that make different predictions are logically inconsistent. The standard model of QM is wrong. General relativity is wrong. No-one here disagrees with this. However, the true theory of the laws of physics, when we obtain it, will have to explain all the experimental observations we have so far, which are predicted by the standard model to within 1 part in a billion in some cases. "The wheel of science ratchets forward, but never back" etc etc.
But you're right, in that all this quantum mechanics stuff is really beside the point anyway. You can apply the generalized anti-zombie principle in a newtonian or any other world just as easily (eg. as done in the first half of the article). Whether or not epiphenomenal particle-tags exist, they can't affect the physical cause of you saying "yes, I have continuing subjective identity", so they can't affect subjective identity. You don't have to assume that epiphenomenal particle-tags don't exist to conclude that they are irrelevant by, er, definition.
The only difference QM makes is that it doesn't talk about "particles" as fundamental entities, and hence "swapping two identical particles" is explicitly a no-op, which is nice, but not much more than an intuition pump.
Replies from: steven0461↑ comment by steven0461 · 2011-06-05T19:26:36.383Z · LW(p) · GW(p)
Philosophers call these particle-tags "haecceities". The SEP has a good article on identity and individuality in quantum theory. From what I can tell, the parent comment is right except in that classical mechanics can be rephrased to not include particles as fundamental entities, and that quantum mechanics can be interpreted to include particles as fundamental entities (e.g. Bohm). Still, having particles be fundamental seems like a much clearer violation of Occam's razor in the quantum case than in the classical case.
Replies from: PhilosophyFTW↑ comment by PhilosophyFTW · 2011-06-07T02:50:44.355Z · LW(p) · GW(p)
I didn't want to come out and talk about haecceitistic properties, since that would have made me sound even weirder (and it is controversial whether there are such), and I was already presenting some arguments in a hostile environment. But I had such properties in mind when responding. Thanks for providing the SEP link.
↑ comment by Mitchell_Porter · 2011-06-05T02:09:35.101Z · LW(p) · GW(p)
Your rebuttal would be more meaningful if you gave us a reason to specifically question the assertion that "identity isn't in specific atoms". Something about QM might have to change, OK; but would it be a part of QM which materially affects Eliezer's argument?
Replies from: PhilosophyFTW↑ comment by PhilosophyFTW · 2011-06-07T02:37:32.372Z · LW(p) · GW(p)
I can't predict what will have to change to get a scientific theory that is correct. Sorry. I'm also not interested in arguing for a theory of identity here. I'm just pointing out that Eliezer's argument against a particular theory of identity fails at being less wrong. I don't have to defend a theory in order to provide a perfectly coherent rebuttal.
Replies from: PhilosophyFTW, Mitchell_Porter↑ comment by PhilosophyFTW · 2011-06-07T03:06:51.828Z · LW(p) · GW(p)
Eliezer might well benefit by thinking about the above-linked SEP article in which this claim is broached: "We now appear to have an interesting situation. Quantum mechanics is compatible with two distinct metaphysical ‘packages’, one in which the particles are regarded as individuals and one in which they are not. Thus, we have a form of ‘underdetermination’ of the metaphysics by the physics (see van Fraassen 1985 and 1991; French 1989a; Huggett 1997). This has implications for the broader issue of realism within the philosophy of science. If asked to spell out her beliefs, the realist will point to currently accepted fundamental physics, such as quantum mechanics, and insist that the world is, at least approximately, however the physics says it is. Of course, there are the well-known problems of ontological change (giving rise to the so-called pessimistic meta-induction) and underdetermination of theories by the data. However, the above underdetermination of metaphysical packages seems to pose an even more fundamental problem, as the physics involved is well entrenched and the difference in the metaphysics seemingly as wide as it could be. These packages support dramatically different world-views: one in which quantal particles are individuals and one in which they are not. The realist must then face the question: which package corresponds to the world? The physics itself can offer no help whatsoever and any justification for choosing one package over the other which appeals to metaphysical considerations, for example, runs the risk of drastically watering down the science in scientific realism."
↑ comment by Mitchell_Porter · 2011-06-07T03:42:19.413Z · LW(p) · GW(p)
In that case, why bring up GR, or even QM? You may as well just say, "Physics might be wrong, ergo, your argument is not deductively valid."
On the other hand, if empirical evidence does count for something in your epistemology, then you need to be addressing the aspect of QM to which he is appealing.
Replies from: PhilosophyFTW↑ comment by PhilosophyFTW · 2011-06-09T03:57:37.814Z · LW(p) · GW(p)
As I have pointed out, the theory to which he is appealing is very probably false. If he wants to appeal to it in defense of his claims (and even then there are several other reasons why his claims almost certainly don't follow from the theory), he needs to do so with much more humility. You don't get to infer P from Q which is probably false, and then assert P with conviction. This is irrational and more wrong (if you know that Q is probably false, which he should), not less wrong. My inference is "The physical theories to which he is appealing are very probably false. This is fact which is widely known. Therefore, his argument is very probably unsound." And that inference goes through. His argument is very probably a load of garbage since it very probably contains a false premise.
I can truthfully say all of that without even beginning to raise problems for his inferences. Of course, I have done this too. His inferences are deeply problematic for numerous reasons, some of which I have mentioned, some of which are raised in the above-linked SEP article, and others of which can be found by taking a look at some of David Chalmer's and Galen Strawson's work.
The post I am commenting on is radically misleading and wildly wrong. Anybody unfamiliar with these issues will be led into error and falsehood by reading it.
Replies from: AlephNeil, Mitchell_Porter↑ comment by AlephNeil · 2011-06-09T07:12:19.981Z · LW(p) · GW(p)
You don't get to infer P from Q which is probably false, and then assert P with conviction.
What if I were to put P = "there is no such thing as absolute simultaneity" and Q = "special relativity"?
Or P = "the earth orbits the sun" and Q = "Newton's theory of gravity"?
Replies from: PhilosophyFTW↑ comment by PhilosophyFTW · 2011-06-10T02:24:22.755Z · LW(p) · GW(p)
What you put in for P and Q is irrelevant, for a simple reason. If you're appealing to Q as your only evidence for P, and Q is probably false, then you don't have good evidence for for P. If Eliezer wants to appeal to some Q as his only evidence for P, and Q is probably false, then he has failed.
Of course, if you have independent evidence for P, then you don't need to appeal to P as your evidence for Q (and you shouldn't, since P is very probably false). Here you can appeal to the independent evidence. For example, there is evidence that the earth orbits the sun that is independent of Newton's theory of gravity. It's for that reason that you find your toy examples plausible.
This doesn't work when we're talking about QM. QM is a package deal that makes predictions. Evidence for the truth of many parts of the package come from the accurate predictions the package makes.
Where there is independent evidence for the parts of the QM package Eliezer wants to appeal to, he should be appealing to those parts of the package and rely upon the independent evidence for them. Appealing to QM is just not rationally acceptable behavior for any reasonably informed persons.
↑ comment by Mitchell_Porter · 2011-06-09T08:34:00.606Z · LW(p) · GW(p)
As AlephNeil points out, theory unification in physics doesn't invalidate everything that came before; quite the contrary. In the passage from classical to relativistic mechanics, you lose absolute simultaneity but you retain conservation laws. In that case, it may also be said that the feature of classical physics that was retained - conservation principles - was something for which there was ample empirical evidence, whereas the feature which was lost - the existence of absolute time - was an ontological presupposition which proved to be dispensable.
I consider your argument from the supposed incompatibility of QM and GR to be a bad argument precisely because it has no evident connection to the aspect of QM which is at stake here. In other posts, Eliezer advocates for Julian Barbour's approach to quantum gravity. There is a small change in the nature of QM here: in Barbour's theory, there is no time evolution. So the conflict is resolved in a way which does not touch Eliezer's argument in this post.
You also mention string theory as a unification of QM and GR from the particle physics side, implying, I suppose, that it is GR which has been modified. That would be a very debatable assertion. It is a commonplace of the string versus loop debate to present strings as an outgrowth of particle physics culture, and loop quantum gravity as an outgrowth of the culture of gravitational physics (relativists), and to say that the string theorists neglect general covariance (or "background independence" as it is usually termed in such discussions). This appears to be a historical contingency; it is now a common belief in string theory that the real observables all exist only on the boundary, precisely because the bulk has diffeomorphism invariance; and meanwhile, for practical purposes, diffeomorphism invariance is just another symmetry, which you break by gauge-fixing for the purposes of calculation, but which will still be there in the predictions (i.e. the effects of gauge-fixing must disappear by the end of the calculation).
It would be very unusual to argue that the unification of QM and GR requires a change in how we think about particle statistics. If you actually had such an argument, it would be worth hearing, but you don't; you just have an argument which bundles the whole of quantum mechanics into one proposition, and the whole of general relativity into another proposition, an argument which claims that the conjunction of these propositions is a contradiction, and that therefore one or the other is false.
Incidentally, how do you get from that to QM is "very probably false"? "The conjunction of A and B is false" does not imply "A is very probably false"! It seems clear that your problem with QM has nothing to do with the alleged incompatibility with GR - this incompatibility (which perhaps you only believe in because of what various authorities say) merely gives you leverage in debate against quantum dogmatists, or hope for a concrete alternative.
Unless you actually have an argument which makes a connection between particle statistics and quantum gravity, you should just stick to particle statistics, and not bring gravity into the picture.
Replies from: PhilosophyFTW↑ comment by PhilosophyFTW · 2011-06-10T02:54:34.015Z · LW(p) · GW(p)
I'm hardly claiming that if we find some true future unified theory of physics, every physical proposition we current believe is false. To assert that would be absurd. The interesting question is which of the propositions that are part of the current packages (at least one of which is false) are in fact false.
If you want to pick some of those propositions and rely upon them, you'd better have independent evidence for their truth (the accurate predictions made by the package isn't going to count). So rely on that as your evidence, and not on the false package. This is what less wrong people would do.
Barbour is engage more in philosophy than in hard science, and his work is published in either published in poor journals or book form. I could care less whether Eliezer endorse Barbour's views, if he does. And if he does, then maybe he'd do better to rely upon them than upon QM. If Eliezer does advocate for Barbour's views, one must wonder why. On the basis of some nice hard scientific evidence? Or on the basis of lots of wishful thinking?
I'm not very interested in getting into a debate about how to properly taxonomize physical theories. That's irrelevant to any of the points I've made, and the debate would be even more irrelevant. Two paragraphs of your response are on this irrelevant subject matter.
It is perfectly acceptable for me to bundle the whole of QM into one proposition, if Eliezer is baselessly relying upon QM. If Eliezer wants to rely on something OTHER than QM, then he can. Something OTHER than QM would be a part of the theory (but not the whole of the theory), or something else like a theory of quantum gravity. If he wants to rely on those things, fine. Then we'll see what the evidence is for what he relies upon. What, for example, is the evidence for treating Barbour's odd-ball theories to be more likely true than, say, a fixed-foliation quantum gravity? Well, there isn't really much evidence. Bad Eliezer.
Your last comment is well worth remarking on. By "very probably false", I roughly meant that there is a 50% probability that it is false. If there is a 50% epistemic probability that P is false, and your belief that Q is based solely upon your belief that P, then you are irrational if you believe that Q.
Replies from: Mitchell_Porter↑ comment by Mitchell_Porter · 2011-06-11T02:20:20.137Z · LW(p) · GW(p)
You know, I made a mistake at the beginning of this discussion, by conceding your premise that QM and GR are inconsistent. I should have just asked to see the proof.
Usually when people say this, they mean that applying the techniques of perturbative quantum field theory (the techniques which produce Feynman diagams) to general relativity gives rise to an unpredictive theory, because there are infinitely many undetermined quantities associated with higher-order terms in the expansion. The philosophy of renormalization is that you measure such quantities and use them to define the renormalized theory, but that this only makes sense when there are finitely many such quantities.
However, there's still no proof that this is true for general relativity. There is a research program, "asymptotic safety", which hopes to find evidence that only finitely many quantities are needed after all. I am skeptical, even though a physicist as good as Steven Weinberg is interested, and as I said, no proof exists. Meanwhile, it does look as if d=4 N=8 supergravity is perturbatively finite. That is a general-relativistic theory - it contains Einstein gravity, coupled to other fields. Although it is perturbatively finite term by term, the Feynman expansion probably doesn't converge, in which case there need to be other contributions, and most likely N=8 supergravity should be considered a limit of string theory.
Anyway, the bad behavior of general relativity when it is treated using the simplest methods of quantum field theory is by far the main reason that people have for talking about QM and GR as inconsistent, and it's a theoretical opinion from several decades ago, that is not borne out by more recent developments. If that's your reason for asserting that QM and GR are inconsistent, I am prepared to rebut that point in as much detail as you wish. If you have some other reason for asserting that they are inconsistent, let's hear it.
(edited to add: undetermined quantities)
comment by Arandur · 2011-08-02T19:42:34.501Z · LW(p) · GW(p)
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?
comment by k3nt · 2011-10-19T05:54:23.036Z · LW(p) · GW(p)
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.
Replies from: khafracomment by QuicklyStarfish · 2012-04-03T19:48:55.082Z · LW(p) · GW(p)
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.
comment by Mader_Levap · 2016-07-25T18:16:55.567Z · LW(p) · GW(p)
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.
comment by [deleted] · 2019-12-26T21:16:10.707Z · LW(p) · GW(p)
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 defeated death and come back to life!
That's a pill I can't swallow. And the nagging doubt which keeps me from going along with that line of argument is: what experience to I anticipate in this scenario? If I'm being scanned now.. I anticipate my life to continue as "original me" at the end of the scanning process and not to suddenly find myself soul-swapped into future "new instance of me."
I've heard people argue that maybe both "original me" and "new instance of me" are entangled and I should expect a 50/50 probability of "ending up" in either manifestation. But that's defeated by further thought experiments: just imagine creating an endless number of replicants in the future. Is the probability evenly split among them all? That would require non-local effects on the probabilities in the present depending on future state, which is highly unlikely.
I've also heard that each time I'm copied or made manifest I should treat that as a 50/50 branch condition. So 50% probability of continuing as original me, 25% as the first copy, 12.5% as the second, etc. We've recovered locality at least, but how does my consciousness persist across a storage medium over the intervening years that doesn't represent a computation? This just substitutes one hard pill to swallow for another.
Furthermore, what should I expect to experience once I die of old age? Do I expect to "wake up" some years later in a younger version of myself, the copy of the earlier scan that was made? Unlikely; I'm not even remotely the same amplitude distribution at that point. This seems even more the product of sloppy thinking than the earlier options considered.
So if I have myself scanned, then die, knowing that someone will "restore" me from the backup copy, my expectation on my death bed is still that I will experience permanent death, oblivion. There will be a new entity constructed which has all my memories up to the point of being scanned, and perhaps that will help lessen the loss felt by those who loved me. But the fact remains: I expect to permanently die when this instance of me dies. The truth that we are all just factors in a subspace of an amplitude distribution doesn't resolve this problem at all.
And there are practical ramifications of this thought experiment: should I sign up for cryonics (preserve this instantiation of me) or brain preservation (destructive copy)? Should I volunteer for destructive mind uploading, once it is available? Etc.
Replies from: Wei_Dai, MichaelStJules↑ comment by Wei Dai (Wei_Dai) · 2020-01-18T07:43:21.932Z · LW(p) · GW(p)
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 [LW · GW] 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 [LW · GW] into a UDT utility function.
↑ comment by MichaelStJules · 2020-05-26T09:47:33.418Z · LW(p) · GW(p)
I 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.
comment by MichaelStJules · 2020-05-26T09:26:30.305Z · LW(p) · GW(p)
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, which I think could be compatible with throwing away time as a fundamental concept.
The atom swap experiment would then destroy both atoms and create two atoms (possibly the same, possibly different, possibly swapped). What we could say about their identities would depend on the precise details of the view. Maybe there's no coherent way to make this work.
(I'm not endorsing such a view, though.)
Replies from: Korz↑ comment by Mart_Korz (Korz) · 2020-05-26T17:48:03.541Z · LW(p) · GW(p)
I 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".
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.
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.
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?
The atom swap experiment would then destroy both atoms and create two atoms (possibly the same, possibly different, possibly swapped). What we could say about their identities would depend on the precise details of the view. Maybe there's no coherent way to make this work.
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 function is defined on the space of unordered tuples, e.g. {r_1,r_2}. Here, 'exchange particles' is not meaningful as {r_1, r_2} and {r_2, r_1} per definition describe the same thing.
**) There are significant consequences: As the space that the wave function moves in is changed drastically, its behaviour also changes. E.g. everything solid builds on the Pauli principle, which is a consequence of identical particles