In cryonics advocacy, the motivation is to avoid dying, but the patient is clinically dead and thus their body and brain are severely damaged at the point when the procedure is initiated. To complicate matters further, there is significant damage done during cryonics procedures. Thus the entire project is only rational under the assumption that damage can be repaired by future technology. However, given hypothetical the prospect of revival, there can be some confusion about if the person is truly dead or not.
The term Information-theoretic death is based on the concept of entropy as relates to physical damage to the brain and the loss of information. It is the destruction of the information within a human brain (or any cognitive structure that may constitute a person) to such an extent that recovery of the original person is theoretically impossible by any physical means. The concept of information-theoretic death emerged in the 1990s as a response to the progress of medical technology since conditions previously considered as death, such as cardiac arrest, are now reversible, so they can no longer define death.
The term 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 survival. 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.
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[by whom?] to occur gradually after many hours of clinical death at room temperature as the brain undergoes autolysis. It may also occur more rapidly 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. Exactly when complete and total information-theoretic death might occur with respect to different types of preservation and decomposition might also be relevant to the speculative field of mind uploading. Taken to the limits imposed by physical laws, it is not known that information-theoretic death ever occurs. Physical information is not known to be destroyed, except by the controversial black hole information paradox; and as such, resuscitation is not specifically ruled out by the laws of physics, unless information critical to that resuscitation passes beyond the event horizon of a black hole. Additionally dispersion of information may make resuscitation physically impossible, if it is to such an extent that the precision required for its retrieval is beyond that allowed by the Heisenberg uncertainty principle.
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.
- IMR (International Medical Rights)
- Merkle, Ralph (January–April 1994), "Molecular Repair of the Brain", Cryonics, retrieved 2014-12-27 – via Alcor library online
- Pro/con ethics debate: When is dead really dead?
- Ethics review: Dark angels-- the problem of death in intensive care
- Albert Einstein’s brain and information-theoretic death
- Medical Time Travel by Brian Wowk