Information-theoretic death is the destruction of the human brain (or any cognitive structure capable of constituting a person) and the information within it to such an extent that recovery of the original person is theoretically impossible by any physical means. In practice, this means that
entropyThe laws of thermodynamics, in principle, describe the specifics for the transport of heat and work in thermodynamic processes. Since their inception, however, these laws have become some of the most important in all of physics and other types of science associated with thermodynamics.It is wise to...
must be reversed in order to revive a person from their last functional brain state (this impossibility is known as
time translation asymmetryT Symmetry is the symmetry of physical laws under a time reversal transformation —Although in restricted contexts one may find this symmetry, the observable universe itself does not show symmetry under time reversal, due to the second law of thermodynamics.Hence time asymmetries are generally...
).
Information-theoretic death is the destruction of the human brain (or any cognitive structure capable of constituting a person) and the information within it to such an extent that recovery of the original person is theoretically impossible by any physical means. In practice, this means that
entropyThe laws of thermodynamics, in principle, describe the specifics for the transport of heat and work in thermodynamic processes. Since their inception, however, these laws have become some of the most important in all of physics and other types of science associated with thermodynamics.It is wise to...
must be reversed in order to revive a person from their last functional brain state (this impossibility is known as
time translation asymmetryT Symmetry is the symmetry of physical laws under a time reversal transformation —Although in restricted contexts one may find this symmetry, the observable universe itself does not show symmetry under time reversal, due to the second law of thermodynamics.Hence time asymmetries are generally...
). 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 arrestA cardiac arrest, also known as cardiopulmonary arrest or circulatory arrest, is the abrupt cessation of normal circulation of the blood due to failure of the heart to contract effectively during systole....
, become reversible and are no longer considered to be death.
"Information-theoretic death" is intended to mean death that is absolutely irreversible by any technology, as distinct from
clinical deathClinical death is the popular term for cessation of blood circulation and breathing. It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest. The term is also sometimes used in resuscitation research....
and
legal deathLegal death is a legal pronouncement by a qualified person that further medical care is not appropriate and that a patient should be considered dead under the law. The specific criteria used to pronounce legal death are variable and often depend on certain circumstances in order to pronounce a...
, 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 nanotechnologyMolecular nanotechnology is the concept of engineering functional mechanical systems at the molecular scale. An equivalent definition would be "machines at the molecular scale designed and built atom-by-atom". This is distinct from nanoscale materials...
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 theoryInformation theory is a branch of applied mathematics and electrical engineering involving the quantification of information. Historically, information theory was developed by Claude E. Shannon to find fundamental limits on compressing and reliably storing and communicating data...
.
The paper
Molecular Repair of the Brain by
Ralph MerkleRalph C. Merkle is a researcher in public key cryptography, and more recently a researcher and speaker on molecular nanotechnology and cryonics...
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 deathClinical death is the popular term for cessation of blood circulation and breathing. It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest. The term is also sometimes used in resuscitation research....
at room temperature as the brain undergoes
autolysisIn biology autolysis or more commonly known as self digestion refers to the destruction of a cell through the action of its own enzymes. It may also refer to the digestion of an enzyme by another molecule of the same enzyme....
. It can also occur if there is no blood flow to the brain during life support, leading to the decomposition stage of
brain deathBrain death is a legal definition of death that refers to the irreversible end of all brain activity due to total necrosis of the cerebral neurons following loss of blood flow and oxygenation. It should not be confused with a persistent vegetative state...
, or during the progression of degenerative brain diseases that cause extensive loss of brain structure.
"Information-theoretic death" also arises in the context of
cryonicsCryonics is the low-temperature preservation of humans and animals that can no longer be sustained by contemporary medicine until resuscitation may be possible in the future. Currently, human cryopreservation is not reversible, which means that it is not currently possible to bring people out of...
, which can be viewed as the use of
cryopreservationCryopreservation is a process where cells or whole tissues are preserved by cooling to low sub-zero temperatures, such as 77 K or −196 °C . At these low temperatures, any biological activity, including the biochemical reactions that would lead to cell death, is effectively stopped...
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.
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