Personally , I’d like to see more discussion of the possibilities of (a) an effectively omnipotent far-future civilization that can just revive everyone by, e.g., scanning the planet and running physics backwards, or time-travel, or whatever, and (b) all those infinite copies of me. Not to mention (c) regular old quantum immortality. All these effects tend to point to “why bother with cryonics?”.
(I have a feeling that Eliezer’s answer to (b) would be something like “Make yourself into the kind of person who would (just shut up and) be immortal”, but I don’t really want to get into the dangerous sport of Eliezer-simulating.)
The only thing that distinguishes quantum immortality from old-fashioned probabilistic immortality (play Russian roulette as much as you like, and if you survive then it turns out that you survived, duh) is the idea that all those possible-yous are real. In which case, relying on “quantum immortality” means just letting the vast majority of them die. If cryonics offers a substantial chance of greatly increasing the proportion of possible-yous that have good long happy lives, then “there’s always quantum immortality” seems to me no reason at all to pass up that chance.
Imagine that you are going to be put into a machine that will replace you with a million copies, all of them having exactly the same degree of physical and psychological continuity with your present self as you generally expect your near-future selves to have. You have (now, before going into the machine) the choice of two actions, one of which means that all but one of those million copies will die horribly tomorrow, and one of which means that only one of them will. The second choice has a moderate cost associated with it. Which way do you choose? I go for the second, for sure.
In the case of your machine, I would have a 999999/1000000 chance of experiencing death if I choose the first option, and 1/1000000 chance with the second. I would most likely choose the second.
But in the case of cryonics, the experience of death is guaranteed; the only question is how many “copies” wake up later. And I have no intuition or logical argument that a million copies of me is better than one.
Maybe I didn’t understand what you were saying about quantum immortality, then. Let’s make it a bit more explicit. To avoid confusion let’s ignore (1) other copies of you that exist merely because the universe is very large, if any, (2) simulations of you that exist for any reason at all, if any, and (3) the possibility that you might escape death without either cryonics or extreme good luck, for instance because of a technological singularity in the near future.
1. Ignoring many-worlds quantum stuff:
Without cryonics, you will almost certainly die within the next (say) 100 years, but there is an infinitesimally tiny chance that you will somehow survive much longer.
With cryonics, you will certainly “die” (that is, go through something that greatly resembles death up to and beyond the point at which you cease to be conscious), and then there’s some chance (whose size is debatable) that you will later be revived.
Comparing these two outcomes, you should decline to bother with cryonics (even if its costs are very low) if (a) you think the chance of getting revived is very tiny, or (b) what matters to you is having some chance of survival rather than having as much chance of survival as possible.
2. With many-worlds quantum stuff:
Every statement that used to be about probability now gets a reinterpretation in terms of (speaking loosely) “number of versions of you”. If you toss a coin, roughly half of your versions see it come up heads and roughly half see it come up tails. If you play Russian roulette with a six-shooter, roughly 5⁄6 of your versions live and roughly 1⁄6 die.
So you should feel exactly the same way about “proportion of versions of me for which X is true” as you do about “probability that X is true for me”.
Now:
Without cryonics, almost all your versions die within (say) 100 years. An infinitesimally tiny fraction of them get “lucky” and live much longer.
With cryonics, all your versions “die”, and then some (debatable how large) fraction get revived later.
Comparing these two outcomes, you should decline to bother with cryonics (even if its costs are very low) if (a) you think the fraction of versions-of-you that get revived is very tiny, or (b) what matters to you is having some copy of you survive rather than having as many copies survive as possible.
And, once again: if you take many-worlds seriously—which you have to, for “quantum immortality” to make any sense—then you should feel exactly the same way about this as you did about the corresponding comparison stated in terms of probabilities: because that’s what probabilities (of the “objective” sort) are. Probability of survival == fraction of Everett branches on which you survive.
If you’re happy for your survival to depend on quantum immortality, then you should also be happy for it to depend on a coin toss or the result of a game of Russian roulette. If quantum immortality doesn’t lessen your reluctance to bet your life in those ways, then it also shouldn’t make a difference to your feelings about cryonics.
an effectively omnipotent far-future civilization that can just revive everyone by, e.g., scanning the planet and running physics backwards
How much physics have you studied? Scanning the planet would not be enough. You’d need something like a timeslice through the future light cone of the point you wanted. This would be a huge volume of space.
Time travel is probably impossible, or if it is possible, then our current understanding of reality is so badly wrong that this entire discussion is probably nonsense.
Quantum immortality is somewhat deceptive… if you buy into it you’ll become apathetic (“there’s always some branch of the wavefunction where what I want happens, so why should I bother?”). Similar comments apply to “all those copies of you” in an infinite universe.
How much physics have you studied? Scanning the planet would not be enough. You’d need something like a timeslice through the future light cone of the point you wanted. This would be a huge volume of space.
I haven’t studied much physics. Would scanning the planet not be enough? Humans, and human brains, have some predictable structure, so if you were smart about things, it isn’t like you’d have to be able to run backwards an arbitrary physics. You’d just to have to be able to make a good probabilistic guess about those portions of a particular state you cared about (the portions that made people “themselves”, which you could conceivably infer by, say, having a notion of the probability space “human brains/minds”, and by having footprints, bits of writing, etc. left by the person at various points in their life). I don’t know how to evaluate the odds here.
Due to QM the function is many-to-one and can’t be reversed. If you isolate a single Everett branch and look only at that branch and not all the other branches, and run that branch backward in time, it will evolve into a multiplicity of pasts (that would in the greater scheme be coherently canceled out by the past evolution of other branches). The upshot is that even if you timeslice the entire future lightcone in a single branch you cannot get the exact past. And we can’t get photons that have escaped over the horizon, so we can’t get the whole future lightcone anyway, and small divergences will amplify, and the whole thing would require more computing power than all the particles we’re trying to run back.
And a time camera using new physics violates the character of known physical law, in particular its elegant locality, that each element of reality only interacts with immediate neighbors.
It’s too early to give up hope. But as a working assumption, the dead are dead.
If you isolate a single Everett branch and look only at that branch and not all the other branches, and run that branch backward in time, it will evolve into a multiplicity of pasts (that would in the greater scheme be coherently canceled out by the past evolution of other branches). The upshot is that even if you timeslice the entire future lightcone in a single branch you cannot get the exact past. And we can’t get photons that have escaped over the horizon, so we can’t get the whole future lightcone anyway, and small divergences will amplify, and the whole thing would require more computing power than all the particles we’re trying to run back.
Then use the quantum ‘probability’ distribution over pasts to randomly pick a person to instantiate (more properly, pick a past and instantiate everyone in it). If you got the distribution right, then each resurrectee has the same relative measure they did before they died (original measure times fraction of worlds in which you do this). Obviously, you can also do this with subjective probability distributions derived from locally available information.
Just how much good this does for the dead is hard to say.
Um… I think the vast majority of false pasts you got this way would be nothing like the real past. I think they may even end up with higher entropy, i.e., arrow of time runs forward from here after a brief reversal (in the vast majority of extrapolated pasts).
Okay, that would mean you can’t just run the physics backward, but that shouldn’t stop the Bayesian method (come up with a prior over histories of Earthlike worlds or some similar class, update on memories, records, etc.) or computationally feasible approximations thereof.
For most people in the past, we have no footprints, bits of writing, etc. A crude back-of-envelope calculation suggests that maybe it takes ~ 10^15 bits to describe one person’s brain; I wouldn’t be surprised to find that wrong by a couple of orders of magnitude, but in any case it’s rather a lot. Anyone who’s (1) in the not-very-recent past and (2) not exceptional in the traces they leave behind has left only very subtle such traces—which will be tied up in computationally intractable ways with everyone else’s very subtle traces, and with all kinds of extraneous cruft. I’ve no idea what might turn out to be possible in principle, and saying “we’ll never have the technology to do X” doesn’t have a great track record of success … but I wouldn’t hold out much hope of being able to retrieve enough information to reconstruct past people even with future-lightcone-scanning technologies, never mind without.
Personally , I’d like to see more discussion of the possibilities of (a) an effectively omnipotent far-future civilization that can just revive everyone by, e.g., scanning the planet and running physics backwards, or time-travel, or whatever, and (b) all those infinite copies of me. Not to mention (c) regular old quantum immortality. All these effects tend to point to “why bother with cryonics?”.
(I have a feeling that Eliezer’s answer to (b) would be something like “Make yourself into the kind of person who would (just shut up and) be immortal”, but I don’t really want to get into the dangerous sport of Eliezer-simulating.)
The only thing that distinguishes quantum immortality from old-fashioned probabilistic immortality (play Russian roulette as much as you like, and if you survive then it turns out that you survived, duh) is the idea that all those possible-yous are real. In which case, relying on “quantum immortality” means just letting the vast majority of them die. If cryonics offers a substantial chance of greatly increasing the proportion of possible-yous that have good long happy lives, then “there’s always quantum immortality” seems to me no reason at all to pass up that chance.
Imagine that you are going to be put into a machine that will replace you with a million copies, all of them having exactly the same degree of physical and psychological continuity with your present self as you generally expect your near-future selves to have. You have (now, before going into the machine) the choice of two actions, one of which means that all but one of those million copies will die horribly tomorrow, and one of which means that only one of them will. The second choice has a moderate cost associated with it. Which way do you choose? I go for the second, for sure.
In the case of your machine, I would have a 999999/1000000 chance of experiencing death if I choose the first option, and 1/1000000 chance with the second. I would most likely choose the second.
But in the case of cryonics, the experience of death is guaranteed; the only question is how many “copies” wake up later. And I have no intuition or logical argument that a million copies of me is better than one.
Maybe I didn’t understand what you were saying about quantum immortality, then. Let’s make it a bit more explicit. To avoid confusion let’s ignore (1) other copies of you that exist merely because the universe is very large, if any, (2) simulations of you that exist for any reason at all, if any, and (3) the possibility that you might escape death without either cryonics or extreme good luck, for instance because of a technological singularity in the near future.
1. Ignoring many-worlds quantum stuff:
Without cryonics, you will almost certainly die within the next (say) 100 years, but there is an infinitesimally tiny chance that you will somehow survive much longer.
With cryonics, you will certainly “die” (that is, go through something that greatly resembles death up to and beyond the point at which you cease to be conscious), and then there’s some chance (whose size is debatable) that you will later be revived.
Comparing these two outcomes, you should decline to bother with cryonics (even if its costs are very low) if (a) you think the chance of getting revived is very tiny, or (b) what matters to you is having some chance of survival rather than having as much chance of survival as possible.
2. With many-worlds quantum stuff:
Every statement that used to be about probability now gets a reinterpretation in terms of (speaking loosely) “number of versions of you”. If you toss a coin, roughly half of your versions see it come up heads and roughly half see it come up tails. If you play Russian roulette with a six-shooter, roughly 5⁄6 of your versions live and roughly 1⁄6 die.
So you should feel exactly the same way about “proportion of versions of me for which X is true” as you do about “probability that X is true for me”.
Now:
Without cryonics, almost all your versions die within (say) 100 years. An infinitesimally tiny fraction of them get “lucky” and live much longer.
With cryonics, all your versions “die”, and then some (debatable how large) fraction get revived later.
Comparing these two outcomes, you should decline to bother with cryonics (even if its costs are very low) if (a) you think the fraction of versions-of-you that get revived is very tiny, or (b) what matters to you is having some copy of you survive rather than having as many copies survive as possible.
And, once again: if you take many-worlds seriously—which you have to, for “quantum immortality” to make any sense—then you should feel exactly the same way about this as you did about the corresponding comparison stated in terms of probabilities: because that’s what probabilities (of the “objective” sort) are. Probability of survival == fraction of Everett branches on which you survive.
If you’re happy for your survival to depend on quantum immortality, then you should also be happy for it to depend on a coin toss or the result of a game of Russian roulette. If quantum immortality doesn’t lessen your reluctance to bet your life in those ways, then it also shouldn’t make a difference to your feelings about cryonics.
How much physics have you studied? Scanning the planet would not be enough. You’d need something like a timeslice through the future light cone of the point you wanted. This would be a huge volume of space.
Time travel is probably impossible, or if it is possible, then our current understanding of reality is so badly wrong that this entire discussion is probably nonsense.
Quantum immortality is somewhat deceptive… if you buy into it you’ll become apathetic (“there’s always some branch of the wavefunction where what I want happens, so why should I bother?”). Similar comments apply to “all those copies of you” in an infinite universe.
I haven’t studied much physics. Would scanning the planet not be enough? Humans, and human brains, have some predictable structure, so if you were smart about things, it isn’t like you’d have to be able to run backwards an arbitrary physics. You’d just to have to be able to make a good probabilistic guess about those portions of a particular state you cared about (the portions that made people “themselves”, which you could conceivably infer by, say, having a notion of the probability space “human brains/minds”, and by having footprints, bits of writing, etc. left by the person at various points in their life). I don’t know how to evaluate the odds here.
Due to QM the function is many-to-one and can’t be reversed. If you isolate a single Everett branch and look only at that branch and not all the other branches, and run that branch backward in time, it will evolve into a multiplicity of pasts (that would in the greater scheme be coherently canceled out by the past evolution of other branches). The upshot is that even if you timeslice the entire future lightcone in a single branch you cannot get the exact past. And we can’t get photons that have escaped over the horizon, so we can’t get the whole future lightcone anyway, and small divergences will amplify, and the whole thing would require more computing power than all the particles we’re trying to run back.
And a time camera using new physics violates the character of known physical law, in particular its elegant locality, that each element of reality only interacts with immediate neighbors.
It’s too early to give up hope. But as a working assumption, the dead are dead.
Then use the quantum ‘probability’ distribution over pasts to randomly pick a person to instantiate (more properly, pick a past and instantiate everyone in it). If you got the distribution right, then each resurrectee has the same relative measure they did before they died (original measure times fraction of worlds in which you do this). Obviously, you can also do this with subjective probability distributions derived from locally available information.
Just how much good this does for the dead is hard to say.
Um… I think the vast majority of false pasts you got this way would be nothing like the real past. I think they may even end up with higher entropy, i.e., arrow of time runs forward from here after a brief reversal (in the vast majority of extrapolated pasts).
Okay, that would mean you can’t just run the physics backward, but that shouldn’t stop the Bayesian method (come up with a prior over histories of Earthlike worlds or some similar class, update on memories, records, etc.) or computationally feasible approximations thereof.
I agree but find the wording in your comment confusing… especially the part after “i.e.” (ironically)
For most people in the past, we have no footprints, bits of writing, etc. A crude back-of-envelope calculation suggests that maybe it takes ~ 10^15 bits to describe one person’s brain; I wouldn’t be surprised to find that wrong by a couple of orders of magnitude, but in any case it’s rather a lot. Anyone who’s (1) in the not-very-recent past and (2) not exceptional in the traces they leave behind has left only very subtle such traces—which will be tied up in computationally intractable ways with everyone else’s very subtle traces, and with all kinds of extraneous cruft. I’ve no idea what might turn out to be possible in principle, and saying “we’ll never have the technology to do X” doesn’t have a great track record of success … but I wouldn’t hold out much hope of being able to retrieve enough information to reconstruct past people even with future-lightcone-scanning technologies, never mind without.