[gwf]

This is a really nice argument and I hope that Kevin and others continue to pursue it. However, I think there is a subtle flaw in the presented argument that is parallel to issues illuminated by Goedel's incompleteness theorem. The problem, I believe, is with the assertion:

> 1. The many-worlds interpretation is true.

> 2. Consciousness experiences the reality in which it lives the longest.

> If all the previous assumptions are true, then at least one of these two must be false.

Both of these statements can be simultaneously true if we allow for a third possibility that is logically consistent with the entire argument:

3. Having near logical certainty and awareness that quantum immortality is true is fundamentally incompatible with living on the subjective immortal multiverse timeline.

This would actually be a robust assumption to have explicitly included at the start, as it also makes intuitive sense. Afterall, if you absolutely knew that quantum immortality was true, then you could (and likely would) walk around taking obviously foolish risks without ever experiencing any consequences. Such a universe would basically lack a coherent sense of cause-and-effect from your subjective point of view. And if it was a universe where cause-and-effect don't hold for you, then how could you have logical certainty about anything?

This means that if quantum immortality is true, you can never have logical certainty of its truth.

This is very similar to how Goedel's incompleteness requires that there be true statements that can't be proven as true because the existence of an explicit proof would negate the statement itself, breaken the consistency of the system of logic (and, hence, making it incomplete by necessity).

[perl4ever]

If quantum immortality is true, and I, knowing that, step in front of a car, how is it going to prevent my bones from breaking?

I remember a haunting fantasy short story about a boy in a small town who accidentally meets and becomes friends with the man who digs all of the graves. Eventually he notices that somehow, the gravedigger knows when a grave is needed before a person dies, but won't say how or who. Often it is possible to guess though. One day, he's told that he'll never guess who the next grave is for, and indeed, he can't. So that night he finds out his parents have been in an auto accident, and therefore one of them is presumably going to die...and so he goes back and kills the gravedigger and buries him in the grave that was intended for one of his parents.

The rest of the story is that once the gravedigger is dead, people in the town stop dying...but that is not a good thing - first his mother is paralyzed, then she has a stroke, then there is a fire... And the end is that the murderer becomes the new gravedigger to restore normality and now old, he hopes for someone to relieve him of the job.

[jerf]

"If quantum immortality is true, and I, knowing that, step in front of a car, how is it going to prevent my bones from breaking?"

Quantum immortality doesn't promise health. It promises consciousness.

It is in fact a horrible idea and you better damned well hope it is false, because it looks a lot less like "I'm going to live forever in at least some fraction of the multiverse and be healthy and happy!" and rather a lot more like SCP-2718 [1]. Probably without the pain in question, but certainly with your consciousness stuck in a body that is literally minimally capable of being conscious and nothing else, past the heat-death of the universe, until the point where even quantum randomness isn't enough to keep you conscious, assuming that such a point can even arrive. QI doesn't protect your mobility, your senses, your health or happiness... just your consciousness. On the plus side, "minimal consciousness" doesn't necessarily entail a great deal of awareness of time passing.

[1]: http://www.scp-wiki.net/scp-2718 , for those not familiar with the format of the site, be sure to click the "► Play" on the bottom for the text I'm referring to. On the topic of SCP, the "End of Death" canon rather resembles your story, albeit moreso: http://www.scp-wiki.net/end-of-death-hub

[red75prime]

It also doesn't necessarily entail remembering who you are. So I think it's not that horrible: you lose more and more of your memories and your capabilities of forming thoughts and intentions, until it's just generic consciousness aware of itself doing nothing and of (what's left from) input stimuli.

[dhimes]

So, in the limit it's not observably different from death? Then it's death.

[jerf]

It's all the things. QI is basically just an consciousness-centric view of the already-understood truth that in the quantum multiverse, everything that can possibly happen does. It just means that there is some way in which you may actually experience some aspect of that, because your future conscious experience excludes all the universes in which you are not conscious. You can draw a subset of future universes in which you are minimally conscious, in which you're just a wee bit more conscious than that, in which you're conscious enough to be aware of your plight indefinitely, in which as I say in another message you're healthy indefinitely. You're not causing anything to be or not to be, you're just carving various subsets of radically differing, but non-zero, size out of the near-infinity of the full quantum multiverse, which exist whether or not you choose to regard them.

So, you know, in a fraction of the universes in which you remain conscious that would require something like 1 over a number in arrow notation to describe, you'll be conscious enough to be perturbed. This is utterly, utterly dominated by the universes in which you're just sort of there. However, if you then choose to exclude those latter universes on the grounds that you consider that to be "dead", then that brings that tiny fraction back to the fore by virtue of eliminating everything else.

It's a lot of definition chopping and manipulating rather enormous exponentials in the probabilities. However, there is still an underlying truth there, if the multiverse is true. It's just more subtle than the casual human view of "survival" or a brief gloss of the argument might entail. You have to think in quantum terms about whether or not this spin goes that way or the other, not in human terms like whether or not the gun fires. The latter is made up of an incomprehensibly large number of the former sort of things, and as you start talking about the fringe cases the quantum events require staggeringly enormous exponential probabilities to describe anything even remotely human-visible.

[red75prime]

Branching of multiverse on every measurement event is an approximation. The branches aren't fully isolated. I suspect that extremely low amplitude branches undergo merger events, which makes it impossible to have coherent timeline in them. But I'm completely out of my depth here.

[dhimes]

Great explanation. Thank you. And, I got to look up "arrow notation." I had never heard of it.

[TheOtherHobbes]

The other view is that QI is literally true, and it literally proves the existence of an immortal soul which transcends whatever happens to the body.

So consciousness can never be killed. But it can be temporarily inconvenienced.

The problem with this argument is that the universe continues to operate when we're asleep, in a coma, etc.

It's almost as if it has an independent existence that doesn't rely on our personal experience of it.

[akvadrako]

QI is usually explained in terms of many worlds, where there is an objective reality independent of our experience.

Those concepts aren’t incompatible, if that’s what you were suggesting by your last sentence.

[gpderetta]

>If quantum immortality is true, and I, knowing that, step in front of a car, how is it going to prevent my bones from breaking?

Your body quantum-tunnels [1]through the car and emerges un scathered on the other side. IANAP, but I believe it is technically possible although the probability is astronomically close to zero. Butif QI is true, you would experience it. It is an example of the apparently logical impossilities that the parent is referring to if I understand correctly.

[1] or fails to interact, or whatever. Again, IANAP.

[perl4ever]

Yeah, but if consciousness is the invariant, then there are vastly more futures in which I don't tunnel through the car but just barely avoid brain-death.

And when I say vastly, I'm pretty sure the ratio is larger than the number of particles in the universe squared.

[mannykannot]

Under many worlds, the you who did not step in front of the car avoids broken bones.

If there is anything to quantum immortality, it is only in those circumstances where the probability of immediate death is strictly between 0 and 1. I suspect, however, that quantum immortality is merely the tautology that survivors, and only survivors, survive, and has nothing to do with interpretations of the QM formalism.

[vankessel]

Thank you. I really like the point you are making, but I am unsure about a lack of cause and effect. When I think of cause and effect, I think of it as taking the state of the universe from state t+0 to t+1 using the laws of physics. All of it being deterministic, except for quantum mechanics. This indeterminism in QM creating the branches allowing one to escape death.

Couldn't believing in quantum immortality be compatible with this? You could do things like firing a gun to your head, and it would misfire every time. You could jump off a building and would land in a passing open-topped garbage truck full of soft material. You'd experience all sorts of crazy coincidences, but all of them plausibly deniable and within the framework of cause and effect as we know it.

With that said, I feel like what you are saying is true but can not fully formulate my thoughts on it yet. I agree completely that you can never have logical certainty of it's truth, but I'm not certain it's contingent on it being true. Perhaps we should instead say that QI is either true or false, but we can never prove which? This removes the implication but still makes sense in the context of Godel's first incompleteness theorem.

[Iv]

I find the whole QI following so weird... Do people really argue that QM can provide cartoon-like effects like a convenient truck under the bridge?

Do people really argue that conscience is so special that the universe refuses to end one?

The universe don't differentiate between a dead human and a living one. From a QM point of view, both body masses, correctly placed, can work as an "observer" to cause waveform collapse.

[vankessel]

Well, yes. Those examples were chosen to be cartoonish stereotypes. Extremely statistically unlikely events would look... strange, to say the least. Sort of like the flapping of a butterfly's wings resulting in a hurricane.

Also there has been some discussion about how quantum events would only affect the microscopic and the macroscopic would remain the same. This is false, quantum events can only occur in the microscopic, but their effects can propagate to the macroscopic in ways beyond our comprehension. Take the experiment itself, the outcome of a quantum event propagates to the life or death of a human being.

Lastly there have also been remarks about how death needs to be guaranteed because QI only promises consciousness not health or a lack of suffering. I will address that here too. That is a perfectly fine way of viewing QI but there is a distinction we should formalize to make it clear.

Greedy QI and Perfect QI.

Greedy QI just branches from the present moment to whichever consciousness will persist. This can result in a local optimum where you are maimed but alive.

Perfect QI always picks the best branch point of every present moment to account for all future possibilities. I argue this in assumption #2. Once the bullet has say, pierced the brain stem, there is no greedy choice from there that will save you. Perfect QI likely won't maim you as that would limit your survival possibilities. It's the global optimum.

There is still a problem with this though. What if there is more than one timeline where you always live? How is one chosen? My guess would be either it's randomly chosen, or there is only one timeline. Let me elaborate on the latter with a mathematical analogy.

You have an infinite list of real numbers. These numbers represent different timelines, the value being how long you survive. If you order them, you can always find a larger finite number looking at the next one, but none of them are infinite in value. Since QI assumes immortality not longevity we will assume the limit of this ordered list is infinity and not a finite number. Thus there is one reality in which you live infinitely, and that's the limit of this ordered set. The only chance for approaching this limit is through a mechanism like perfect QI.

[jerf]

"Do people really argue that conscience is so special that the universe refuses to end one?"

QI doesn't protect consciousness. Its argument applies to any quantum state, described by any arbitrarily complicated acceptance function of that state. The QI argument implies that you can pick up a rock, and that there exists some set of universes in which that rock will survive indefinitely, exactly as it is now, to any degree of accuracy you care to specify. It's just the more precise your specification gets, the lower the probability mass is.

That's why in my other message, I say QI only promises consciousness. Technically, there are universes in which by sheer quantum chance you are in fact healthy and happy indefinitely. It's just that "a healthy and happy body" is incomprehensibly more orders of magnitude more unlikely than being stuck in whatever constitutes the minimally conscious body. And in fact, the latter isn't a unique construct either. It's actually a function of the selectivity you apply to the acceptance function; you have the universes in which you are conscious enough to realize your plight, but they're dominated by the universes in which you are too minimally conscious to even realize that, which are in turn dominated by the universes in which you are just not conscious. But those are excluded from your consciousness' future states, which means your consciousness is left over with whatever else is left.

The distinctive thing that consciousness adds to the argument is merely that if you metaphorically drew out the future universes in which your consciousness survives, there is something meaningful (to us, anyhow!) "inside" that set. You can do the same thing to the rock as I described above, but there isn't really anything "inside" that set; it's just the rock and nothing else. Excepting of course that vanishing fraction of the universes in which quantum processes drive the rock to become conscious by any definition of your choice, of course.

(Another thing I'd point out is that for this discussion, I have no concern about what your definition of "consciousness" is. The argument works regardless of your definition, it just tweaks the exact non-zero numbers that come out.)

[Iv]

Why should it bring more comfort than knowing, e.g. that there are alternative universes where my deceased loved ones are alive?

There seems to be a belief that our consciousness will "jump" to an alive alternative. I think that's a strong misconception of what many-worlds interpretation says.

Talking about misconceptions, without having more than superficial background in QM, I doubt that being able to consider even very unlikely outcomes allows you to discard macroscopic causality altogether, which QI basically requires.

[jerf]

"Why should it bring more comfort than knowing, e.g. that there are alternative universes where my deceased loved ones are alive?"

I'm not sure you're reading my posts for what they say, rather than what you expect them to say. I think QI is horrible, as in, more suited to horror stories, than something that offers comfort. Nor do I discuss any sort of "jumping".

[jerf]

"Couldn't believing in quantum immortality be compatible with this? You could do things like firing a gun to your head, and it would misfire every time. You could jump off a building and would land in a passing open-topped garbage truck full of soft material. You'd experience all sorts of crazy coincidences, but all of them plausibly deniable and within the framework of cause and effect as we know it."

I think one of the several issues I have with this article is that you're measuring survival in human terms, not quantum terms. One of the secret constraints in the quantum suicide thought experiment is that your method of death must be literally 100% guaranteed, and ideally for the argument, instantaneous from the point of view of your consciousness. (That is, for our consciousness's sake, I don't think Planck time is particularly relevant; more human time frames are relevant.) Sometimes this is expressed as sitting next to an atom bomb rather than just a gun.

But, even then, as a pragmatic matter, a real person trying to perform this experiment would need to be concerned about the quantum probability that the bomb does indeed go off, but leaves them maimed because it didn't exactly explode fully, but the explosives half-detonate and the uranium goes only a bit critical, spraying you with radiation and seriously injuring you but not actually killing you. As you sit there next to your quantum number generator, you are indeed systematically pruning the quantum state space of the worlds in you do actually die, but the remaining quantum state space has a great deal more than just "you get up and turn off the quantum number generator once you are satisfied".

Similarly, a gun can do a lot more than just fire and kill you, or not fire and leave you harmless. It could fire, and put what should be a fatal hole in your head, but the bare minimum quantum events occur to keep you just barely conscious.

As you prune away all the likelihoods, you're amplifying the probably of everything other than what you pruned away, not just the human-conceivable events. The harder and more successfully you prune, the weirder what's left over gets. Given that you've set up a situation in which you've got a gun aimed at your head or an atom bomb or what have you, those "weird" situations are likely to be unpleasant.

Of course, if QI and the multiple worlds hypothesis is correct, this all happens anyhow all the time, and seeing our family or friends just suddenly explode for no reason is something we are literally experiencing all the time, just with such a low probability that it hasn't happened yet. But, somewhere in the great multiverse, there's a set of people who read this message and it is immediately followed by, say, their left hand just disintegrating. Take heart... for some yet smaller fraction of you, it will also immediately fix itself.

[whatisthiseven]

> Afterall, if you absolutely knew that quantum immortality was true, then you could (and likely would) walk around taking obviously foolish risks without ever experiencing any consequences.

On the contrary, wouldn't it be the case that all the "yous" that did such a thing died, leaving only the "yous" that attempted only a small fraction of risky events? Just because many worlds is true, it doesn't mean all possibly infinite combinations of things also exist (e.g. PI is infinite, but it doesn't contain all possible combinations of numbers, nor itself).

[ars]

> you could (and likely would) walk around taking obviously foolish risks without ever experiencing any consequences

Only things that are random on a quantum level cause world splitting.

Walking in front of a car for example is not random on a quantum level and would not cause multi-world effects.

In the popular consciousness multiple worlds means every single possibility exists. This is not true!

In fact there are very few macro effects that are caused by quantum randomness. Even if multiple worlds is true they are all identical except microscopically.

[rblatz]

It’s my understanding that radioactive decay is a quantum random.

Radioactive decay emits particles that can interfere with dna and cause cancer.

So some number of people would have/not have cancer in these many worlds. Not all these people would have profound impacts, but the background noise would start to add up quickly.

[marcofiset]

> if you absolutely knew that quantum immortality was true, then you could (and likely would) walk around taking obviously foolish risks without ever experiencing any consequences.

What if you get put on a path where you eventually die because of your recklessness, and that was the longest you would have stayed alive? Basically you already exhausted all possible paths but this one.