Information-theoretic death is the scrambling of information within a brain to such an extent that recovery of the original person becomes theoretically impossible.
Information-theoretic death is an attempt to define death in a way that is permanent and independent of any future medical advances, no matter how distant or improbable that may be.
Because detailed reading or restoration of information-storing brain structures is well beyond current technology, it is generally not of practical importance in "mainstream medicine",  though it is of great importance in cryonics, where consideration of future technology is important.
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. If the structures in the brain that encode memory and personality have been so disrupted that it is no longer possible in principle to recover them, then the person is dead. If they are sufficiently intact that inference of the state of 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.
So defined, information-theoretic death has been called "the ultimate definition of irreversible death", and "absolutely irreversible death" in which "destruction of the brain has occurred to such an extreme that any information it may have ever held is irrevocably lost for all eternity".
Information-theoretic death has propagated into some mainstream bioethical, biophilosophical and religious discussions of death, and was mentioned in a 2007 Newsweek article on advances in treating cardiac arrest.
- Sebastian Seung (2012). Connectome: How the Brain's Wiring Makes Us Who We Are. Houghton Mifflin. p. 271. ISBN 9780547678597.
Merkle's definition of death is of more philosophical than practical importance. To apply it, we need to know exactly how memories, personality, and other aspects of personal identity are stored in the brain.
- Merkle R (September 1992). "The technical feasibility of cryonics". Medical Hypotheses. 39 (1): 6–16. doi:10.1016/0306-9877(92)90133-W. PMID 1435395.
- Cerullo MA (March 2016). "The Ethics of Exponential Life Extension Through Brain Preservation" (PDF). Journal of Evolution and Technology. 26 (1): 94–105.
This is known as the information-theoretic definition of death and appears to be the ultimate definition of irreversible death.
- Doyle DJ (2011). "Life, Death and Brain Death: A Critical Examination". Ethics in Biology, Engineering and Medicine. 2 (1): 11–31. doi:10.1615/EthicsBiologyEngMed.2011003293.
In the later case, sometimes called “absolutely irreversible death” or “information theoretic death” destruction of the brain has occurred to such an extreme that any information it may have ever held is irrevocably lost for all eternity.
- Whetstine L, Streat S, Darwin M, Crippen D (October 2005). "Review: Pro/con ethics debate: When is dead really dead?". Critical Care. BioMed Central. 9 (6): 538–542. doi:10.1186/cc3894. PMC . PMID 16356234.
This approach to defining death, which is rooted not in relative, changing technology and vitalistic worldviews, but rather in the fundamentals of physical law, is known as the information theoretic criterion of death.
- Crippen DW, Whetstine LM (February 2007). "Ethics review: Dark angels – the problem of death in intensive care". Critical Care. BioMed Central. 11 (1): 202. doi:10.1186/cc5138. PMC . PMID 17254317.
Cryptographer and nanotechnologist Ralph Merkle noted, “The difference between information theoretic death and clinical death is as great as the difference between turning off a computer and dissolving that computer in acid.
- Ali Afzali M (December 2013). "Brain death from the perspective of shia and modern medicine" (PDF). Journal of Mazandaran University of Medical Sciences. 24 (113): 221–233.
The theory of information-theoretical death was introduced, stating that the human brain cell arrangement at one point in time loses its stored information and experiences brain death (translate.reference.com)
- Wowk B (December 2014). "Special Section. "Death by Neurologic Criteria 1968-2014: Changing Interpretations": The future of death". Journal of Critical Care. Elsevier. 29 (6): 1111–1113. doi:10.1016/j.jcrc.2014.08.006. PMID 25194588.
One possible answer is a definition of death that is independent of technology, no matter how advanced. Such a definition is the Information Theoretic Criterion for Death.
- David Crippen (2011). "The problem of death in critical care medicine". In Singh, Mamta B; Bhatia, Rohit B. Emergencies in Neurology. Byword Books. pp. 396–404. ISBN 8181930673.
Any meaningful definition of death is then suggested by an information-theoretic criterion. In other words, does that patient contain enough undamaged structure (information) to infer his healthy working state from his current non-functional one?
- Hughes JJ (2004). "The Death of Death". In Machado C, Shewmon A. Brain Death and Disorders of Consciousness, Advances in Experimental Medicine and Biology, Volume 550. Springer. pp. 79–88. ISBN 030648482X.
We will soon need to scrap the brain death standard in favor of a much more tentative, probabilistic, information-theoretic understanding of death as the loss of identity-critical information.
- Newsweek Staff (22 July 2007). "Back to Life: The Science of Reviving the Dead". Newsweek.
(Ralph Merkle) has used this idea to popularize a fourth definition of death: "information-theoretic" death, the point at which the brain has succumbed to the pull of entropy and the mind can no longer be reconstituted. Only then, he says, are you really and truly dead.