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The philosophical problems people have with identity may seem silly, but many people are affected by it. Some people who may otherwise have no problems with cryonics or other preservation techniques will choose guaranteed death because they don't intuitively think their consciousness will persist. That is why I think it is so significant. People who doubt for practical reasons can be convinced in time if the technology comes up to speed, but those who deny it for philosophical reasons may never be convinced regardless of technological advancements.
An easy ...
My honest take on this is that it's completely missing the point. There is an assumption here that your future self shares an identity with your current self that other people don't, which is called Closed Individualism. People tend to make this assumption without questioning it, but personally, I assign it < 1% of being true.
I think it's fair to say that, if you accept reasoning of the kind you made in this post (which I'm not claiming is wrong), you can prove arbitrarily absurd things about identity with equal justification. Just imagine a procedure for uploads that does not preserve identity, one that is perfect and does, and then gradually change one into the other. Either identity is a spectrum (???), or it can shift on a single atom (which I believe would contradict #4).
The hypothesis that you share identity with everyone (Open Individualism) is strictly simpler, equally consistent with everyday experience, has no compatibility issues with physics, and is resistant to thought experiments.
I'm not saying that Open Individualism is definitely true, but Closed Individualism is almost certainly not true, and that's enough to be disinterested in cryonics. Maybe you share identity with your upload, maybe you don't, but the idea that you share identity with your upload and not with other future people is extremely implausible. My impression is that most people agree with the difficulty of justifying Closed Individualism, but have a hard-coded assumption that it must be true and therefore think of it as an inexplicably difficult problem that must be solved, rather than drawing the conclusion that it's untrue.
"There is an assumption here that your future self shares an identity with your current self that other people don't, which is called Closed Individualism."
I actually wrote the argument for people who believe in Closed Individualism. I myself subscribe to Open Individualism. The purpose was to convince people who subscribe to Closed Individualism to not reject cryonics on the basis that their identity will be lost. Some people, even if revived after cryonics, may worry that their identity has fundamentally changed which can lead to an existential crisis.
"I...
#5 Science and observation is necessary and sufficient to evaluate claims regarding the physical world and the mind.
We clearly know that this is false. Heisenberg's uncertainty principle clearly demostrates that there are claims about the physical world that we can't evaluate as through or false through observation and science.
Eliezer wrote in the sequences about how he believes it to be false with regards to the Many-World Hypothesis.
If observation is not a sufficient standard, then what is?
Eliezer wrote the sequences to lay out a standard.
Ok, #5 was a bit strong for this, though I must argue that Heisenberg's uncertainty principle itself was discovered through observation. Using a claim justified by observation and experiment to undermine the sufficiency of observation with regards to evaluating claims in general seems off to me.
If a change or thing has no observable effects, how can one claim that that change or thing exists? Eliezer himself believes that the Many-Worlds Hypothesis has observable effects, namely anthropic immortality, which can be tested if one is willing.
Bayesian updating...
I can't say anything on this subject that Derek Parfit didn't say better in Reasons and Persons. To my mind, this book is the starting point for all such discussions. Without awareness of it, we are just reinventing the wheel over and over again.
Even if the technology to restore a preserved brain or upload it into a simulation becomes viable technologically and monetarily people may still reject it for philosophical reasons. Practical problems can be solved through sufficient research and design, but philosophical problems may never go away.
Bah. Philosophical problems can easily go away with peer pressure.
Suppose the technology for uploading is reliable and cheap. Some people will try it. Then some of their friends will. At some moment, a celebrity will upload, followed by many fans and copycats.
When someone in your social circle has uploaded, you can either accept them as being "them", or stop interacting with them... the remaining option, meeting them regularly and saying: "You are not the real John; the real John is dead, and left you as a fake ghost" is emotionally difficult. So most people will accept the uploads.
(This is true regardless of whether the philosophical problems are right or wrong.)
This is the argument of the beard. You can pluck one hair from a bearded man and he still has a beard, therefore by induction you can pluck all the hairs and he still has a beard.
Or if you stipulate that replacing N neurons not merely causes no "significant" change, but absolutely no change at all, even according to observations that we don't yet know we would need to make, then you've baked the conclusion into the premises.
If I continually pluck hairs from my beard then I have noticeably less of a beard. Eventually I will have no beard. Replacing some neurons with the given procedure does not change behavior so the subject cannot notice a change. If the subject noticed a change then there would be a change in behavior. If you assert that a change in consciousness occurred, then you assert that a change in consciousness does not produce a change in consciousness to notice it.
We can fall asleep without noticing, but there is always a way to notice the changes. One can decide t...
Consider reading Scott Aaronson's The God in the Quantum Turing Machine, it goes in considerable depth stating and answering the questions such as
Could there exist a machine, consistent with the laws of physics, that “non-invasively cloned” all the information in a particular human brain that was relevant to behavior—so that the human could emerge from the machine unharmed, but would thereafter be fully probabilistically predictable given his or her future sense-inputs, in much the same sense that a radioactive atom is probabilistically predictable?
The answers are not obvious and certainly not amenable to a "simple proof".
You assume that the conscious part of the brain consists of interacting but independent subunits, whose only property of significance is how they interact with their neighbors.
This is not the only ontological option. For example, there is the quantum notion of entanglement. There may exist a situation in which there are nominally two entities, but the overall quantum state cannot be reduced to one entity being in one state, and the other entity in a second state.
Consider a state of two qubits. If the overall state is |01>, that can be decomposed into |0>|1>. But a superposition like |01>+|10> cannot.
There is a further issue of whether one ascribes reality to quantum states. In the (original, true) Copenhagen interpretation, quantum states are not real things, that role is reserved only for observables and only when they take definite values.
However, if one's ontology says quantum states are things that exist, and if the conscious part of the brain is one big entangled state, then you can't just replace the parts independently. There may be other operations you can perform, like quantum teleportation, but what they signify or allow, in the way of identity transfer, is unclear (at least, in the absence of a definite quantum theory of consciousness).
I am very concerned with the general attitude towards cryonics and body preservation in general. People who reject these as worthwhile as far as I can tell fall into two primary camps: the probability of revival is too low to justify the monetary sacrifice or that personal identity is not transferred in the revival process. The first issue does not worry me much. Restoring brain function or some equivalent is an engineering problem, a practical problem. Monetary cost is an unfortunate problem, but it is also a practical problem. The other issue however is more of a philosophical one. Even if the technology to restore a preserved brain or upload it into a simulation becomes viable technologically and monetarily people may still reject it for philosophical reasons. Practical problems can be solved through sufficient research and design, but philosophical problems may never go away.
Regarding synthetic brains or brain simulations, I have heard time and time again people claiming that any brain created in such a way will not have the same identity as the original. If someone's brain is scanned while he or she is alive and a synthetic or simulated brain is created and run, then I agree that two separate identities will form. The problem, I think, is that people imagine this particular situation and generalize its conclusion to all possible scenarios regardless of context. Obviously if the scan is performed after the original brain ceases to function there will not be any parallel consciousnesses to diverge from each other.
Some people will then argue that a synthetic brain or simulation cannot even in principle carry over the original consciousness, that personal identity is not transferred. I will try to provide an informal sketch of a proof here of the contrary, that personal identity for all intents and purposes can be transferred over to a synthetic or simulated brain.
Assumptions:
#1 There is a brain device that manifests consciousness using neurons or some functional equivalent. It may be a natural biological, synthetic, simulated brain, or a mixture of these.
#2 There is a procedure that is to be performed on the brain device that will replace some neurons with functional equivalents such that neurons in the unaltered regions of the brain device will not behave any differently throughout time in the presence of the replaced neurons than they would if no neurons were replaced as long as the external stimuli (sight, touch, smell, etc.) is the same in both cases. This procedure, even if every neuron is replaced in one go, is completed faster than the individual neurons can react so that it won't lag behind and cause syncing issues between the unreplaced and replaced neurons. For the case of uploading one can imagine that neurons are removed and sensors are placed there to record what would have been the inputs to the removed neurons. A computer calculates what the outputs of the removed neurons would have been and sends this output to a biological interface connected to the unremoved neurons.
#3 There is a placebo procedure that gives the subject the appearance of the actual procedure having been performed without any neurons actually being altered.
#4 There exists a number N such that if any N neurons of a brain device without any degraded consciousness are altered while not affecting any other neurons, then the brain device will not suffer any significant cognitive impairment. This basically means that a small portion of the brain device can be altered without a significant loss to consciousness or identity, even if those portions are completely removed.
#̶5̶ ̶S̶c̶i̶e̶n̶c̶e̶ ̶a̶n̶d̶ ̶o̶b̶s̶e̶r̶v̶a̶t̶i̶o̶n̶ ̶i̶s̶ ̶n̶e̶c̶e̶s̶s̶a̶r̶y̶ ̶a̶n̶d̶ ̶s̶u̶f̶f̶i̶c̶i̶e̶n̶t̶ ̶t̶o̶ ̶e̶v̶a̶l̶u̶a̶t̶e̶ ̶c̶l̶a̶i̶m̶s̶ ̶r̶e̶g̶a̶r̶d̶i̶n̶g̶ ̶t̶h̶e̶ ̶p̶h̶y̶s̶i̶c̶a̶l̶ ̶w̶o̶r̶l̶d̶ ̶a̶n̶d̶ ̶t̶h̶e̶ ̶m̶i̶n̶d̶.̶
#5 Consciousness can observe and evaluate all aspects of itself relevant to itself.
Proof:
Suppose the procedure is performed on N neurons of the original brain device. By #4 the subject does not incur any significant impairment. The subject does not notice any degradation in consciousness or identity or any change at all compared with the placebo procedure, for if it did then it would cause a behavior change to reflect this which is impossible since the replaced neurons are functionally equivalent to the originals and the unaltered neurons will behave the same as if no neurons were replaced.
There is not, even in principle, a method for observing a degradation of consciousness or identity after N neurons are replaced by the procedure since the replaced neurons are functionally equivalent to the originals. If the subject noticed any change whatsoever then the subject could, for example, raise a finger to signify this. But the subject's behavior is the same whether the actual procedure or placebo were carried out. As long as the subject is given the same external sensory information, the subject cannot distinguish which procedure took place. From an internal point of view the consciousness cannot distinguish any degradation or change of any kind in itself. By #5, there must not have been any alteration relevant to consciousness. Assuming that consciousness and identity is an aspect of consciousness, then there is no degradation of either.
Assume that the procedure will not degrade the mind if performed on kN neurons, where k is some positive integer. Suppose the procedure is performed on kN neurons of the original brain device. The resulting brain device does not have degraded consciousness. Perform the procedure on an additional N neurons with a negligible lapse in time since the former replacement. By assumption #2, altering N neurons on a non-degraded brain device will not cause any significant effect to its mind so the mind is still capable of evaluating any potential changes to its consciousness. Furthermore, since the N neurons just replaced are functionally equivalent to the originals the behavior of the brain device cannot be different from the placebo procedure that gives the subject the appearance that the N neurons were replaced. Since the behavior is indistinguishable from the placebo, the subject cannot have noticed a change or degradation in consciousness for if it did a difference in its behavior would signify this. As explained previously, there is no method even in principle for the subject to observe any degradation since its behavior is unaltered in any case. By #5, the procedure of replacing (k + 1)N neurons will not cause any degradation or change of consciousness or identity.
By mathematical induction, the procedure performed on kN neurons will not cause any degradation to consciousness or identity for all positive integers k where kN is less than or equal to the total number of neurons in the brain device.
I do not know how high N can be for human brains, but based on brain damage survivors it is likely to be quite high. N is at least 1. Therefore any number of neurons can be replaced by the procedure in a single iteration without any observable degradation. This implies that the entire brain device can be replaced in one go without any degradation.
This informal proof can be made much more general and rigorous. For example by replacing closed volume regions instead of individual neurons since the brain uses more than just neurons to function. Regions could be replaced with devices that interact with the region boundaries in functionally the same way as the original material. One can go into arbitrary detail and specialize the argument for cryonically preserved people, but I think the general point of the argument is clear. The argument can be extended to neurons that have partially random behavior. The conclusion would be the same regardless.
Imagine that someone developed such a procedure. How would one evaluate the claim that the procedure does or does not degrade consciousness or identity? A philosophical or metaphysical system could be applied to generate an absolute conclusion. But how could one know that the philosophical or metaphysical system used corresponds to the actual universe and actual minds? Observation must decide this. If one accepts that different philosophies of mind with different conclusions each have a probability of being true, then observation must be what narrows down the probabilities. If one is less than certain of one's own philosophical conviction, then one must observe to decide. My proof was a thought experiment of what would occur if one were to experimentally test whether the procedure affects consciousness. Consciousness itself is used as the standard for evaluating claims regarding consciousness.
Do you all find this reasonable? Crucially, do you all think this might convince the people who deny synthetic and simulated brains for philosophical reasons to not choose death for the sake of philosophy. Dying for philosophy is, in my opinion, no better than dying for religious dogma. Science, observation, and grounded reason should be the evaluator of physical and mental claims, as I hope my arguments reflect.
Update
After reading the comments and thinking over the matter I can see how people can justifiably disagree with this.
I used the term consciousness vaguely. Replacing a part of the brain with a functional equivalent does not alter the future behavior of the neurons that are unreplaced. However, the unaltered part of the brain not being able to tell a difference does not necessarily imply that consciousness was not altered. One can conceive that the removed part had consciousness inherent in it that may not be manifested in the same way in the new replacement part even though the rest of the brain does not react differently.
Corpus callosotomy severs the connection of one half of a brain from the other half. People seem to retain consciousness after the procedure and each side of the brain then acts independently, presumably with independent consciousness. This implies that consciousness is manifested throughout the brain.
If the right side of the brain is replaced with a synthetic one that interacts with the left side of the brain in the same way, then the left side doesn't notice a difference. However, the left side does not necessarily know if the consciousness in the right side is now manifested in the same way or manifested at all.