Most people, given the option to halt aging and continue in good heath for centuries, would. Anti-aging research is popular, but medicine is only minimally increasing lifespan for healthy adults. You, I, and everyone we know have bodies that are incredibly unlikely to make it past 120. They're just not built to last.
But what are you, really? Your personality, your memories, they don't leave you when you lose a leg. Lose most parts of your body and you're still you. Lose your brain and that's it. [1] You are a pattern, instantiated in the neurons of your brain. That pattern is sustained by your body, growing and changing as you learn and experience the world. Your body supports you for years, but it deteriorates and eventually isn't up to the task any more. Is that 'game over'?
Perhaps we could scan people's brains at extremely high detail so we could run them in some sort of human emulator. This requires a thorough understanding of the brain, huge amounts of storage, unbelievably fast computers, and very detailed scanning. If it's even possible, it may be several hundred years away.
Our bodies aren't going to last that long, but what if we could figure out how to preserve our brains so that the information didn't decay? Then, if the future turned out to be one in which we had advanced brain emulation and scanning technology, we could be revived. I don't know if people in the future would want to spend the time or money to revive us, but in a future with technology this advanced, reviving a preserved brain as a computer simulation could be really cheap.
The most advanced technology for long-term tissue preservation today [2] is cryonics: freezing with vitrification. You add something to the blood that keeps ice crystals from forming and then freeze it. This is pretty much the same thing frogs do, hibernating frozen through the winter. The biggest organs that have been successfully brought back to working order after vitrification are rabbit kidneys, and the brain is a lot bigger and much more complex. While there are people applying this technique to human brains after death, it's very much a one way street; we can't revive them with current technology.
How much should it worry us that we can't reverse this freezing process? If we're already talking about revival via high-detail scanning and emulation, which is only practical after hundreds of years of technological development, does it matter that we can't currently reverse it? The real question in determining whether vitrification is sufficient is whether we're preserving all the information in your brain. If something critical is missing, or if something about our current freezing process loses information, the brains we think are properly preserved might be damaged or deteriorated beyond repair. Without a round trip test where we freeze and then revive a brain, we don't know whether what we're doing will work.
Another issue is that once you've frozen the brain you need to keep it cold for a few centuries at least. Liquid nitrogen is pretty cheap, but providing it constantly over such a long time is hard. Organizations fall apart: very few stay in business for even 100 years, and those that do often have departed from their original missions. Current cryonics organizations seem no different from others, with financial difficulties and imperfect management, so I don't think 200+ years of full functioning is very likely.
Even if nothing goes wrong with the organization itself, will our society last that long? Nuclear war, 'ordinary' war, bioterrorism, global warming, plagues, and future technologies all pose major risks. Even if these don't kill everyone, they might disrupt the cryonics organizations or stop technological development such that revival technology is never developed.
Taking all these potential problems and risks into account, it's unlikely that you can get around death by signing up for cryonics. In attempts to calculate overall odds for success from estimated chances of each step I've seen various numbers: 1:3, 1:4, 1:7, 1:15 and 1:400. I'm even more pessimistic: I calculated 1:600 when I first posted to lesswrong and have since revised down to 1:1000. To some people the probability doesn't matter, but because it's expensive and there are plenty of other things one can do with money, I don't think it's obviously the sensible thing to do.
(I also posted this on my blog.)
[1] Well, lose your heart and you're gone too. Except that we can make mechanical hearts and you stay the same person on receiving one. Not so much with a mechanical brain.
[2] Plastination is also an option, but it's not yet to a point where we can do it on even a mouse brain.
In spare hours every month or three, I've been working on a questionnaire and calculation system to elicit background beliefs about cryonics so as to be able to capture people's opinions about the value of cryonics (even if they are "I would pay money to avoid it because it sounds really cold"). The idea is to be able to give this instrument to lots of people and let a sort of "wisdom the the crowds" process work on each separate element of the value calculation and then be able to play some of the insights back for specific people to bring them into some kind of sane conclusion on the subject, fixing their "outlier beliefs" on particular questions by showing them information many other people thought lead to different conclusions. I totally do not have this in final form but it has helped me form more than normally educated opinions on the subject.
From what I can tell, the place I part company with people who have already signed up without substantial calculation was in the estimate of the long term value of post-resuscitation life. (Well, that and I don't like the investment options normally used to pay for it, given other possible uses for my time and money. If life insurance options were held constant and 10-year 20% real return TIPS were for sale, it would probably be a slam dunk yes to get 10 year term cryo-policy and pour money into the TIPS.)
A lot of people seem to assign basically infinite value to their own post-resuscitation life. One basis for this is that they simply take continued existence as the most fundamental value there is, a sort of "there is no amount of money a person wouldn't pay for a medical treatment that would give them some chance versus no chance" attitude. I don't share this attitude. There are things I'd die for (thermodynamic obliteration death, not just heart/brain cessation), and some of these things could be accomplished by relatively prosaic amounts of money like $500 million, hence it seems clear to me that my life is probably worth less than this. To me, people who have an infinitely self-valuing attitude seem like immortalist versions of utility monsters, and so it doesn't seem like a compelling pitch on a virtue ethical basis... though I imagine that someone could produce some sort of "poetry" to change my aesthetic responses somehow?
The other way people get an almost infinite value is to believe that intentional or negligent death would never happen post-resuscitation (no suicide, no murder, no accidents) and thus they expect to happily live for something like a trillion years, and any fraction of a chance at this is "worth it". This argument seems somewhat plausible to me, and it is my basis for continuing to think that the value of information on cryonics is kind of high, especially if I can develop an inter-subjectively compelling instrument for spelling out the value calculation for many people that is consistent with this reason. It seems like a factual question and if the conclusion comes out a certain way, and people can be convinced of it by the iterated application of basically prosaic reasoning that as yet no one on the planet (including me) possesses, then the acquisition and deployment of this set of reasons would be worth trillions of years times billions of lives and it is one of the most important things that anyone currently alive could do, unless they can do something that entails this as a trivial consequence.
But my own gut feeling at this point is that there probably exists a small but non-negligible "probability that I'd commit suicide in year Y, for arbitrary dates" that would apply to me post-resuscitation unless my mind was forcibly modified by external processes. The ethical framework I'm partial to suggests that, in this case, my "mental self" would have become a mere puppet in the service of the manipulating entity (which was presumably racking up trivial-hedon-points (or some such)?)... but I'd actually prefer to die with some measure of personal integrity rather than end up in that kind of boring and moderately degrading infinite loop. I want something like "a self-directed life with narrative integrity", not just repetition of some semi-mechanical notionally-point-worthy action. But if I don't accept a self-modification to make suicide impossible, then the expectation curve for "me being alive N years after resuscitation because I still haven't exercised my right to kill myself" probably becomes pretty small within a century or five (especially as my mind gets out into the zone past 130 where no human psychology has ever existed to permit interpolative base rate justification).
So at this point, the huge value of information argument still kind of applies and it is the thing that motivates me when I work on my questionnaire, but the thing I'm conceptually interested in is something like "speculative positive geronto-psychology" which is data-poor and hard to make progress in. What would a cognitively and spiritually happy 220 year old person be like? What would their intellectual interests be? Would they be impatient to reach 300 because the people that old seem world-wise and spiritually developed to them? Would it be creepy cradle robbing for them to be in a sexual relationship with someone who was merely 100 years old because the 100-year-old was so naive and vulnerable? Would they be utterly incapable of learning new technology or new skills because the the 25 year opportunity cost hit if they tried to change specialties was too much to handle?
It is now a stereotype for people to have a "mid life crisis" somewhere between 38 and 55. Is there something else with similarly noticeable internal structure (that would acquire a name once it started happening and people started noticing it) that lurks in human souls waiting to trigger somewhere between 138 and 182, like a "sesquicentennial crisis" or something? If there is such a thing, how many people decide to kill themselves over it? Maybe a set of inferences click into place at some point and everyone you might naively want to stay alive realizes: "Oh yeah. Nihilism. Duh... That was ironic" and they pull the plug. Presuming a mathematical model of psychological processes that justifies very long term psychological optimism seems naive. It could be I just haven't found the right approach yet, but it seems like post resuscitation life expectancies of 300 years are vastly more plausible than post resuscitation life expectancies of 300 thousand years (and 300k really would justify a cryo-policy that had a 0.1% chance of working... it just seems unlikely to me that this is how things would play out).
So anyway, I don't have any particular answer here. I'm still working on it. But my questions are no longer the ones I normally hear other people being interested in so I thought I'd gloss the issues here where they might get eyeballs to see if this causes other people to update or they have some kind of interesting feedback. Maybe my peculiar brand of virtue ethics is naive? Maybe I "should want" to become a subjective utility monster? Maybe being a hedon-puppet isn't as ugly it sounds to me? Maybe I don't really have a solid grasp of how to value a single object sampled from an exponential decay function?
Maybe I should just re-read Permutation City? :-P
I'm still uncertain about a lot of this. The value of information around the general issue still seems pretty high to me. But at the same time it seems to me that the people who have already signed up did so with inadequate philosophically-grounded financial justification. There are still many terrible reasons to not sign up that seem to be blocking most normal people, I'm not denying that... but I have never heard a clean and thorough positive case for cryonics on its own terms without having to stoop to address the many many quibbles raised by people (1) with major cognitive dissonance on the general subject of death and/or who are (2) in the grip of an ugh field around end-of-life planning. Just because many of those quibbles are wrong doesn't mean the conclusion they argue against is right.