If the many worlds of the Many Worlds Interpretation of quantum mechanics are real, there's at least a good chance that Quantum Immortality is real as well: All conscious beings should expect to experience the next moment in at least one Everett branch even if they stop existing in all other branches, and the moment after that in at least one other branch, and so on forever.

However, the transition from life to death isn't usually a binary change. For most people it happens slowly as your brain and the rest of your body deteriorates, often painfully.

Doesn't it follow that each of us should expect to keep living in this state of constant degradation and suffering for a very, very long time, perhaps forever?





I don't know much about quantum mechanics, so I don't have anything to contribute to this discussion. I'm just terrified, and I'd like, not to be reassured by well-meaning lies, but to know the truth. How likely is it that Quantum Torment is real?



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If the many worlds of the Many Worlds Interpretation of quantum mechanics are real, there's at least a good chance that Quantum Immortality is real as well: All conscious beings should expect to experience the next moment in at least one Everett branch even if they stop existing in all other branches, and the moment after that in at least one other branch, and so on forever.

Yes, Quantum Immortality is "real", as far as it goes. The problem is that it is inappropriately named and leads to inappropriate conclusions by misusing non-quantum intuitions. So yes, if you plan to put yourself in a 50% quantum death-box and keep doing so indefinitely you can expect there to be a branch in which you remain alive through 100 iterations. The mistake is to consider this intuitively closer to "immortality" rather than "almost entirely dead".

Doesn't it follow that each of us should expect to keep living in this state of constant degradation and suffering for a very, very long time, perhaps forever?

No. Don't do a count on branches, aggregate the amplitude of the branches in question. We should expect to die. There happen to be an infinite (as far as we know) num... (read more)

(But I'm biased!)

(How do you know? People keep saying it, seriously or not, but when one is aware of a source of a bias, it seems as easy to overcompensate as to undercompensate, at which point you no longer know that you are biased.)

I don't, and I'm sufficiently confident regarding the relevance of said post that a little doubt regarding under or over confidence matters little. On top of that I'm no more biased regarding what I wrote in the past than what I write in any comment I am writing now so additional warnings of bias for a reference call rather than inline text is largely redundant. That was a colloquial usage not a lesswrongian one. It is sometimes appropriate to lampshade self-references so that it does not appear that one is trying to double-count ones own testimony.
Certainly (hence "seriously or not"). It just irks me when people say things whose literal interpretation translates into wrong or meaningless statements, particularly when those statements are misleading or wrong in a non-obvious way. So my issue is with (the use of) such statements themselves, not the intent behind their usage, which in most cases doesn't take the literal interpretation into account. (It's usually possible to find a substitute without this flaw.)
This example fits into a third category. That is, the colloquial meaning is valid, the lesswrong/OvercomingBias connotations are misleading but it is in fact technically true. I am, after all, biased about my own work and that is something that a reader should consider when I link to it. Assuming no difference in prior impressions of Carl and I Carl_Shuman's link should be weighted slightly differently than my own. I agree that I'd be best served to use different wording due to the potentially distracting connotations (do you have suggestions?) but I disagree regarding the actual technical wrongness of the statement.
Wait, what did you mean by "I don't" in the previous comment then? I understood that comment as confirming that you don't know that you are biased, but in this comment you say "I am, after all, biased about my own work". To clarify: by "biased", I mean a known direction of epistemic distortion, a belief that's known to be too strong or too weak, a belief that's not calibrated, and is on the wrong side in a known direction. If the direction of a bias is unknown, it doesn't count as a bias (in the sense I used the word). By this definition, knowing that you're biased means knowing something about the way in which you're biased, that can be used to update the belief until you no longer have such actionable information about its updated state. For example, if you expect that you estimate the quality or relevance of your own post as higher than its actual quality or relevance, this is actionable information to adjust your estimation down. After you do that, you will no longer know whether the adjusted estimation is too high or too low, so you are no longer biased in this sense. (I guess the confusion/disagreement comes from the difference in our usage of the world "bias". What do you mean by "biased", such that you can remain biased about your own work even after taking that issue into account?) (I wasn't able to unpack the statement "That is, the colloquial meaning is valid, the lesswrong/OvercomingBias connotations are misleading but it is in fact technically true.", that is I don't know what specifically you refer to by "colloquial meaning", "LW/OB connotations".)
"I can not reliably state the nature or direction of whatever biases I may have. Even if I was entirely confident regarding the bias I should and in fact do expect others to bear that potential bias in mind."
I've just finished reading your post. Basically what is says is, if I care about reality I should care about all future branches, not just the ones where I'm alive (or have achieved some desired result, like a million dollars). Okay, I get that. I do care about all future branches (well, the ones I can affect, anyway). But here's the thing: I care even more about the first-person mental states that I will actually be/experience. Let's say that a version of me will be tortured in branch A, while another version of me will be sipping his coffee in branch B. From an outside perspective, it's irrelevant (meaningless, even) which version of me gets tortured; but if 'I' 'end up' in branch A, I'll care a whole lot. So yeah, if I don't sign up for cryonics and if Aubrey de Grey and Eliezer slack off too much, I expect to die, in the same sense that I don't expect to win the lottery. I also expect to actually have the first-person experience of dying over the course of millenia. And I care about both of these things, but in different ways. Is there a contradiction here? I don't think there is.
The two senses of "care" are different, and it's dangerous to confuse them. (I'm going to ignore the psychological aspects of their role and will talk only about their consequentialist role.) The first is relevant to the decisions that affect whether you die and what other events happen in those worlds, you have to care about the event of dying and the worlds where that happens in order to plan the shape of the events in those worlds, including avoidance of death. The second sense of "caring" is relevant to giving up, to planning for the event of not dying, where you no longer control the worlds where you died, and so there is no point in taking them into account in your planning (within that hypothetical). The caring about the futures where you survive is an optimization trick, and its applicability depends on the following considerations: (1) the probability of survival, hence the relative importance of planning for survival as opposed to other possibilities, (2) the marginal value of planning further for the general case, taking the worlds where you don't survive into account, (3) the marginal value of planning further for the special case of survival. If, as is the case with quantum immortality, the probability of survival is too low, it isn't worth your thought to work on the situation where you survive, you should instead worry about the general case. Once you get into an improbable quantum immortality situation (i.e. survive), only then should you start caring about it (since at that point you do lose control about the general situation), and not before.
Objectively or subjectively? If the objective measure of the branches is very low, you could round that off to "expect to die"... from someone else's perspective. From your perspective, even if there is one low probability branch where you continue, you can be sure to subjectively experience it, since there is no "you" to experience anything in the high probability branches. But really it's too firm a conclusion to expect to live. There are no facts about MWI and QI because they rely on questions about 1. Probability 2. Consciousness 3. Personal identity that we don't have good answers to.
As far as I know I am already "almost entirely dead" in all possible worlds, so playing with the scant epsilon of universes I exist in doesn't seem like too much of a problem. If there were a way to narrow my measure of existence down to only a single universe in which only the very best things ever happened it seems like that would have the highest utility of any solution. If such a best universe exists it is very, very unlikely. My expected value from its existence is consequently very, very little unless I can prevent my experience in lesser universes. The questions are twofold: Can quantum suicide select such a best universe (is there a cause of the very best things happening that involves continually trying to kill myself; it seems contradictory) and if so, is it the most likely or quickest way to experience such a universe? Clearly an even better goal would be a future where all universes are the best possible universe, but the ability to accomplish that does not seem likely. I lack a sufficient understanding of quantum mechanics (and the real territory) to answer these questions. This is something of a paradox because my dead branches won't experience anything, leaving my experience only in the branches where I live. I should expect to experience near-death, but I should never expect to experience being dead. So a more useful expectation is what my future self will experience in 100 years, 1,000 years, or 1,000,000 years. Probably I will have died off in all but an epsilon of future possible universes, but what will those epsilon be like? They are the ones that matter.
What about anthropics? Should we care more about the worlds where we exist? EDIT: Wait, that's nonsense.
I'd say "ridiculous", not "nonsense". An agent certainly could care about said worlds and not about others. Yvain has even expressed preferences along these lines himself and gone as far as to bite several related bullets. Yet while such preferences are logically coherent I would usually think it is more likely that someone professing them is confused about what they want.
Indeed. I was thinking about subjective probabilities, without noticing that what I expect to observe isn't what I expect to happen when dealing with anthropics. I was pretty tired ...

How likely is it that Quantum Torment is real?

The more conventional perspective on QM is of a single nondeterministic world or of a single world in which events have subquantum causes. From this perspective "quantum torment" - lingering indefinitely in a near-death state - is logically possible but inconceivably improbable, something that wouldn't happen even if you reran the history of the cosmos a googol times, because it involves the quantum dice (whether deterministic or nondeterministic) repeatedly coming up just the right way to prevent your body from finally giving up the ghost.

In a many-worlds theory all logical possibilities are supposed to happen, but the empirically validated probabilities still have to be respected. That is, we don't see all possible events occurring with equal probability, we see them occurring with probabilities given by the Born rule of QM. How to justify this within MWI is a major problem, one of several that the theory faces. But assuming that it is resolved, then the frequency with which quantum torment is realized in the multiverse must be the same as the probability with which it is expected in single-world QM, i.e. it represents a vanishingly small fraction of worlds. In the vast, vast majority of worlds you just die.

If someone is an "identity freak", they need to condition the distribution on "person X is alive" (where "X" -- the person of interest). And now the question is whether the average health deteriorates "as time goes to infinity" -- it probably deteriorates to some minimum livable floor and then bounces up once we cross singularity. (I'm not an "identity freak" BTW.)
To explore some possibilities, have a look at http://www.fanfiction.net/s/5389450/1/The-Finale-of-the-Ultimate-Meta-Mega-Crossover -- where MWI is generalized to what I call "Universal Distribution Metaphysics".
It's much easier to neglect low probability events in a single universe (I should say a finite single universe) where they generally don't occur. If low measure worlds occur, they may well seem fully real to the observers inside them.
It's much easier to neglect low probability events in a single universe (I should say a finite single universe) where they generally don't occur. If low measure worlds occur, they may well seem fully real to the observers inside them.

If the many worlds of the Many Worlds Interpretation of quantum mechanics are real, there's at least a good chance that Quantum Immortality is real as well

Have you read these counterarguments?

I have now, thanks.

Doesn't it follow that each of us should expect to keep living in this state of constant degradation and suffering for a very, very long time, perhaps forever?

No. One can't have it both ways. If your consciousness can persist in some infinitesimal state, then one of the things it will have lost on its way to that state is the ability to feel suffering, or boredom, or a sensation of passing time or anything of the like. The ability to feel suffering isn't any more intrinsically a part of us than the ability to see colors or hear sounds.

Besides (though th... (read more)

Good points!
Being in a infinitesimal measure world is not the same as having infintessimal, zombie like, consciousness. It would be very convenient if it were, but you can't pick assumptions to get to the conclusions you want.

If you're prepared to say you're immortal because even if you die you're still alive in some other branch, it seems like you shouldn't even need quantum mechanics. You're immortal because even if you die, you're still alive in the past.

Sure, but the subjective experience of being my past self will never causally follow from my subjective experience of being the current me, so I don't care. Put another way, you're talking about timeless immortality. I'm talking about real immortality.
The difference between "never" and "with order epsilon probability" is of order epsilon, I wouldn't worry your head about it. And you're not talking about real immortality, that's my point. Quantum immortality is no more real than timeless immortality, and arguably less.
You're talking about a different notion of immortality. As it ignores probability, it doesn't seem to capture the usual concept very well.
For sure, whatever kind of "immortality" it is it certainly isn't something I would tend to describe as "real"!

If in one bazillionth of worlds, right now, you are being tortured even though in every other world you are both alive and well, and you don't care about that world because it's only one in a bazillion, there's no reason to care about that one branch more if all the rest of the branches get changed so that you're dead. The amount you care about it should be independent of the amount you care about all the other branches.

The question "Which branch will I go down?" does not specify different ways-the-world-could-be, depending on whether the answer ... (read more)

What makes you privilege the experience of dying over other, more positive experiences? That is, even if there's a very large number of branches where we experience this suffering, wouldn't there also be very large numbers of a branches containing positive experiences? It's the ratio of positive to negative experiences that matter, not the raw quantity of one or the other.

ETA: That is to say, the reasoning "when I'm close to dead, no matter how likely I am to die in the next instant, at least one branch of me continues on suffering" is symmetric to "man this hot shower is amazing, good thing there at least one branch of me that continues to enjoy it indefinitely."

Well, if I didn't know about MWI, I would believe it to be much more likely that I'll die (in some number of years) than that I'll become a happy immortal. Since I do know about MWI, this translates into a really high Quantum Torment/Quantum Happiness ratio. ETA a response to your ETA: I don't think it's symmetric. There's a next moment for your consciousness whether or not you stay in the hot shower, but there is only a next moment for the consciousness of a dying and suffering person if he keeps living (and most likely suffering). That's the whole point.
But your (main) concern doesn't seem to be death per se, rather the possibility of existing for an extremely long time in the state of almost-being-dead. It is not at all obvious to me why such a possibility carries more weight than the possibility of existing for an extremely long time in the state of being perfectly healthy. In fact it seems like most observer moments over all branches would be biased toward a state of health rather than illness.
As I alluded to in my ETA above, the whole point of quantum immortality is that we'll end up in a really unlikely branch because we won't exist in all the other branches. Are you asking why, once I'm in a state of almost-being-dead, it's likely that the branch I'll be in at the next moment will be one in which I'm still almost-dead, rather than healthy? It's because even if MWI is true, the next moment is caused by the current moment. If my body is deteriorating now and nothing happens to change that, it will be deteriorating in a moment too. Or are you asking why it's more likely I'll end up in a state of almost-being-dead than not in the first place? I've answered that one above.
Hm, I think my confusion is over the idea of quantum immortality in general rather than specific to the torment scenario. If I understand it correctly, QI says that at some point in time there will exist a single branch containing a "me" that, against all odds, never dies. The idea of quantum torture comes from noting that continuing to exist in a state of right-about-to-die would likely be extremely unpleasant. So, what makes this single branch so important? Why is the me in that branch more "me" than a me any given branch that exists with temporally concurrence to other branches? For example, there is probably a branch out there where I am existing in horrible agony at this point in time. I don't see why we should worry about the quantum torture branch and not this branch. They both contain "me." Basically, QI gives more importance to a "me" in a branch that is temporally isolated from "me's" in other branches. I don't see why this is the case or why time should be a factor at all.
What makes the consciousness of the next moment the same consciousness as this moment?
Because the subjective observability constraint doesn't cut off cases where the shower ends badly. Not saying I entirely buy QI - measure clearly means something - but that's how the argument goes.

Aside from all the other reasons for relief offered in this thread, the fact that you're not in Quantum Hell right now is anthropic evidence that QI isn't true in the sense you should be worried about.

(You may note that this is a generalized argument against most possible forms of immortality.)

All conscious beings should expect to experience the next moment in at least one Everett branch even if they stop existing in all other branches, and the moment after that in at least one other branch, and so on forever.

I don't think this is quite true. Rather, if there is precisely one Everett branch in which a conscious being still exists, they should expect to experience it. If there is no such Everett branch, the conscious being will still be conscious in this moment but will not experience any future moments. If there are multiple, the conscious being should expect to experience one of them.

Since others have already covered the physics side of things:

Your problem here is mostly with using confused notions of things like "conciousness", "real", "expect" and "self". As you level up starts grokking thinking in terms of the measure of computations across the tegmark multiverse and the like, these kind of problems will naturally dissolve. (and be replaced by new arguably much worse unrelated ones)

Could you elaborate? On the new unrelated problems.

It sounds like this is a question that you really, truly need to know the correct answer to because you have something to protect. I can sympathise here, because my own journey into rationalism really started when I realised that something extremely bad might happen - something so important that I needed to be sane about it.

When faced with a question that you need the correct answer to, there's some agreement on LW that the right attitude is one of curiosity. Having too much fear can get in the way of clear thinking - and you'll need a lot of clear thinkin... (read more)

In thought experiment (https://en.wikipedia.org/wiki/Quantum_suicide_and_immortality) it says: "Barring life after death, it is not possible for the experimenter to experience having been killed, thus the only possible experience is one of having survived every iteration". QM IMHO does not say about afterlife, so afterlife takes care of Quantum Torment.

I was thinking about this post and thought up the following experiment. Suppose, by some quantum mechanism, Bob has a 50% probability of falling asleep for the next 8 hours and a 50% probability of staying awake for the next 8 hours. By the same logic as QI, should Bob expect (with 100% certainty) to be awake after 2 hours, since he cannot observe himself being asleep? I would say no. But then, doesn't QI fail as a result?

I don't know much about quantum mechanics, so


If you're worried about it, just sign up for cryonics.

I'm afraid that I don't understand. Can you (or someone else) explain?
4Eliezer Yudkowsky11y
If you sign up for cryonics, your "last" moments should have causal continuity with a much larger measure of futures than the QTI ones, so it should be prophylactic against quantum immortality. I hope.
You mean you're not? Seriously Eliezer, without you and Max Tegmark I probably wouldn't even take MWI seriously. You gotta help me. :) Okay.

You mean you're not?

I'm signed up for cryonics. I'm a bit worried about what happens to everyone else.

Going on the basic anthropic assumption that we're trying to do a sum over conditional probabilities while eliminating Death events to get your anticipated future, then depending on to what degree causal continuity is required for personal identity, once someone's measure gets small enough, you might be able to simulate them and then insert a rescue experience for almost all of their subjective conditional probability. The trouble is if you die via a route that degrades the detail and complexity of your subjective experience before it gets small enough to be rescued, in which case you merge into a lot of other people with dying experiences indistinguishable from yours and only get rescued as a group. Furthermore, anyone with computing power can try to grab a share of your soul and not all of them may be what we would consider "nice", just like if we kindly rescued a Babyeater we wouldn't go on letting them eat babies. As the Doctor observes of this proposition in the Finale of the Ultimate Meta Mega Crossover, "Hell of a scary afterlife you got here, missy.&qu... (read more)

Thanks Eliezer. I'll let you know when I've signed up, if you're interested.
Don't forget to claim your Hanson hour, either.
0Paul Crowley11y
I keep remembering mine but am totally daunted by the prospect of claiming it. I feel like I should have some really good stuff lined up to ask about first.
You could always sell it.
0Paul Crowley11y
No, it's precisely because I want to use it a lot that I don't use it :) Anyway, Robin might reasonably feel that all other things being equal, he prefers to spend time talking to the sort of person who does sign up than the sort of person who doesn't.
Robin was the one who suggested selling it in his original post http://www.overcomingbias.com/2009/03/my-cryonics-hour.html (and I think most people would not have thought of selling at all), so apparently he disagrees - talking to a person who would pay for an hour of conversation may also be interesting.
! ! ! Be honest. Are you prescient? And are you using your eldritch powers to troll us?
Doesn't this mean that you should deliberately avoid finding out whether cryonics can actually preserve your information in a retrievable way, because if it can't it would eliminate the vast majority of the worlds that would have brought you back? Whereas if you don't know it remains undetermined. Am I getting this right?
3Eliezer Yudkowsky9y
You're confusing subjective probability and objective quantum measure. If you flip a quantum coin, half your measure goes to worlds where it comes up heads and half goes to where it comes up tails. This is an objective fact, and we know it solidly. If you don't know whether cryonics works, you're probably still already localized by your memories and sensory information to either worlds where it works or worlds where it doesn't; all or nothing, even if you're ignorant of which.
How far do "memories and sensory information" extend? I'm worried about what happens during sleep. It's been argued that dreams are a stability mechanism that prevent self-change, but I don't know if that applies to the external world. Following this line of argument, our memories could change while we are awake if we aren't actively remembering them.

Quantum immortality as you describe it is not a consequence of MWI. It's not true that every single change in an MWI universe is accompanied by branching. Branching occurs when microscopic quantum superpositions decohere, i.e. when interactions magnify microscopic superpositions into macroscopic superpositions. So branching is the consequence of a particular type of physical process: the "measurement" of a microscopic superposition by its macroscopic environment. Not all physical processes are of this type, and its not at all obvious to me that t... (read more)

Okay, this is the kind of argument that, if true and correct, would actually convince me that quantum torment is not real. My extremely limited, incomplete, and non-mathy understanding of QM makes me suspicious of your explanation because it talks about things like macroscopic measurements affecting the fundamental level of reality, and about fundamental events only happening sometimes in special circumstances. But since my understanding is so incomplete, I don't actually trust it. I'll have to rely on other people who understand QM, or give Eliezer's sequence and my physics books another shot! Since this has become such an important topic to me, I don't think I have a choice anymore, anyway. Thanks for the reply.
World-splitting in MWI is not a fundamental event. "Worlds" themselves aren't fundamental objects in the theory. They are imprecisely defined macroscopic entities that emerge from decoherence. So nothing I say involves macroscopic processes affecting the fundamental level of reality. ETA: Perhaps you're thrown off by my use of the word "measurement" because it suggests something vaguely Copenhagish. All I mean by a measurement-type interaction is an interaction between the system and its environment that leads to einselection.
Hmmm... this post has received at least three downvotes at this point. I'm pretty confident that everything I've said here about the MWI is correct, but if someone thinks it isn't, I'm very interested to hear why. So if the downvoting is attributable to perceived factual inaccuracy, could you let me know what you think the inaccuracy is? Thanks.
I have an objection to this: I think that essentially all processes involving macroscopic objects are of this type. My understanding is that the wave function of a macroscopic system at nonzero temperature is constantly fissioning into vastly huge numbers of decoherent sub-regions, i.e., "worlds." These worlds start out similar to each other, but we should expect differences to amplify over time. And, of course, each new world immediately begins fissioning into vast numbers of "sub-worlds." So, while in one world you might get run over by a bus, there is e.g. another world that separated from that one a year ago in which the bus is late and you survive. Plus huge numbers of other possibilities. In this vast profusion of different worlds, for any given death there's essentially always another branch in which that death was averted.
And then there's the branch with extremely small amplitude that separated 30 seconds ago where the bus explodes form proton decay.
I don't think you have any factual inaccuracies.
Most of his premises are approximately correct but applied incorrectly to reach an incorrect conclusion (that is the first sentence). It could be restored by injecting caveats like "for all practical purposes" and "virtually" here but the thing is the whole "Immortality" notion is already ridiculously impractical to begin with. Quantum tunneling through the bus and leaving your arm behind is only a few gagillion orders of magnitude more unlikely than winning Quantum Roulette ten times a day every day for 1,000 years. It is stupid to consider those improbable outcomes as privileged but not wrong.