Immortality as a zero probability of information-theoretic death may not be possible or realistic. A more practical (and less controversial) objective of radical life extension would be to minimize the chance of information-theoretic death. In analogy with Aubrey de Grey’s objective to cure human aging by engineering negligible senescence (SENS), the objective of radical life extension should be to achieve a negligible chance of information-theoretic death. Although curing aging will be necessary, it will be far from sufficient to achieve greatly extended lifespans. Even if aging can be completely abolished by advanced molecular technologies, humans will still be vulnerable to major accidents and homicide. Of course, such events may not necessarily produce acute information-theoretic death, but it can be argued that when humanity becomes more robust and advanced, the nature of accidents (space travel) and murder (“information-theoretic murder”) may become more destructive as well. This raises the question of whether our ability to eliminate “traditional” risk factors can outpace the number and nature of new risks.
Perhaps the most logical proposal to achieve a negligible chance of information-theoretic death is to duplicate a person. If enough duplicates are made, the chance that all of them will die can be made very small. But this raises the issue of whether such duplicates are the same individual. Some people would argue that this strategy does not produce atomistic non-serial immortality. It is also not clear how the question of whether a copy of an individual is the same individual can ever be resolved by empirical observation or logical deduction.
Perhaps the most realistic proposal to reduce the probability of information-theoretic death would be to separate the neurological basis of the person from its body in such a fashion that the risk of complete destruction of the person would become negligible. One such proposal is briefly discussed by Robert Ettinger in his book “Man into Superman.” In Chapter 4 on “Cyborgs, Saucer Men, and Extended Bodies,” Ettinger notes that “the brain need not necessarily be mobile; in fact, it might be better protected and served if fixed at home base. The sensors and effectors–eyes, hands, etc.–could be far away, and even widely scattered, with communication by appropriate signals (not necessarily radio).” Because such an “extended body” would not rely on controversial technologies such as duplication and mind-uploading, the traditional concept of identity can be reconciled with reduced vulnerability. Clearly, this idea could benefit from detailed elaboration and specific proposals.
The prospect of such extended bodies raises an important question about resuscitation of cryonics patients. When should they be revived? Naturally, a necessary condition is the ability to reverse any damaged incurred during the cryopreservation process itself and being able to cure the patient’s terminal disease. Most people who have made cryonics arrangements will add that the general ability to rejuvenate a person should be a necessary condition as well. Because all these conditions require availability of similar technologies, it is doubtful that the choice between these scenarios has practical relevance. A more stringent condition, however, would be a request to only attempt resuscitation if the chance of information-theoretic death is smaller after resuscitation than in long term low temperature care. This option raises an uncomfortable question — are patients in low temperature care safer from information-theoretic death than a person alive today? Answering this questions involves a lot of complicated issues such as the technical feasibility of cryonics, the nature of long term care of cryonics patients, and, ultimately, how one weighs the certainty of being alive today against the probability of a (vastly) longer lifespan in the future.