Information-theoretic death
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Information-theoretic death is the destruction of the human brain, and information within it, to such an extent that recovery of the original mind and person that occupied the brain is theoretically impossible by any physical means. The concept of information-theoretic death arose in the 1990s in response to the problem that as medical technology advances, conditions previously considered to be death, such as cardiac arrest, become reversible and are no longer considered to be death. In particular, the prospect of brain repair using molecular nanotechnology raises the possibility that medicine might someday be able to resuscitate patients even hours after the heart stops. The term "information-theoretic" is used in the sense of information theory.
Information-theoretic death is intended to mean death that is absolutely irreversible by any technology, as distinct from clinical death and legal death, which denote limitations to contextually-available medical care rather than the true theoretical limits of human survival. The paper Molecular Repair of the Brain [1] by Ralph Merkle defined information-theoretic death as follows:
A person is dead according to the information-theoretic criterion if their memories, personality, hopes, dreams, etc. have been destroyed in the information-theoretic sense. That is, if the structures in the brain that encode memory and personality have been so disrupted that it is no longer possible in principle to restore them to an appropriate functional state then the person is dead. If the structures that encode memory and personality are sufficiently intact that inference of the memory and personality are feasible in principle, and therefore restoration to an appropriate functional state is likewise feasible in principle, then the person is not dead.
The exact timing of information-theoretic death is currently unknown. It has been speculated to occur gradually after several hours of clinical death at room temperature as the brain undergoes autolysis. It can also occur if there is no blood flow to the brain during life support, leading to the decomposition stage of brain death, or during the progression of degenerative brain diseases that cause extensive loss of brain structure.
Information-theoretic death also arises in the context of cryonics, which can be viewed as the use of cryopreservation to attempt to prevent information theoretic death. The use of information-theoretic criteria has formed the basis of ethical arguments that state that cryonics is an attempt to save lives rather than being an interment method for the dead. In contrast, if cryonics cannot be applied before information-theoretic death occurs, or if the cryopreservation procedure itself causes information-theoretic death, then cryonics is not feasible.
