Scientific critics of cryonics often do not seem to understand the basics of cryobiology (freezing does not “burst” cells), or remain ignorant that cryopreservation without freezing (“vitrification”) has been a routine procedure in cryonics since 2000. It is not surprising, then, that some advocates of cryonics question the integrity of such critics. Are they deliberately ignoring or distorting the evidence that supports the technical feasibility of cryonics?

One Alcor official has informally called such critics “cryonics deniers.” One might object to using such a strong characterization because the feasibility of cryonics is a conjecture, not a fact. I would like to suggest a more specific kind of denial. Many critics of cryonics seem unwilling to recognize the possibility of repair, or at least not factor it in when evaluating the coherence of arguments in favor of cryonics.

The ultimate goal of cryonics organizations is to offer reversible human cryopreservation (suspended animation) but is proof of suspended animation necessary for cryonics to be plausible?

The answer to this question is a resounding ‘NO.” To reiterate the premise of cryonics; long term care at cryogenic temperatures allows the person to take advantage of medical advances of the future, including cell repair. Cryonics permits the use of an imperfect preservation technique, provided that the damage produced by sub-optimal technologies does not exclude inferring the original state of the brain (or body) from the damaged state. This is a subtle, but important implication of the idea of medical time travel. Pointing out that existing cryopreservation techniques are imperfect does not refute the cryonics premise, unless it can be shown that such techniques produce information-theoretic death.

Not all injuries to the brain can be repaired. For example, when the period of cerebral ischemia is so extensive that bacteria-driven putrefaction has erased most of the brain structure, meaningful restoration is not likely to be possible. Do all sub-optimal cryopreservation technologies that fall short of true suspended animation produce this kind of damage? Not likely! For example, let’s assume that modern vitrification solutions produce some degree of protein denaturation and membrane damage that compromise viability. Is it plausible to argue that this completely renders the idea of repair impossible? Does ice formation produce alterations in the brain that do not allow future “reconstructive connectomics” techniques to infer the non-frozen state from the frozen state? Sweeping claims about “freezing damage” are not acceptable substitutes for detailed structural arguments, especially given the fact that damage incurred during the cryopreservation process is also locked into place by those same low temperatures.

One might object that the idea of cell repair is itself implausible, i.e. that the laws of physics do not permit the idea of healing at the molecular level. The problem with this argument is that human biology already features molecular assembly and DNA repair. Whether one subscribes to the idea of mechanical molecular nanotechnology, modification of viruses or white blood cells, or further miniaturization of 3D printing, it is reasonable to assume that some kind of nanomedicine will be developed in the future.

I once called the idea that human suspended animation is a necessary condition for cryonics to be taken seriously the “Prehoda fallacy.” (Robert Prehoda in the 1960s was an early champion of this position.) It does not serve advocates of cryonics well to discuss the feasibility of cryonics without discussing the plausibility of molecular medicine. If a critic of cryonics claims that cryonics is not technically feasible, insist upon a detailed exposition why the forms of damage associated with today’s technologies cannot be repaired by future medical technologies.

Originally published as a column in Cryonics magazine, May-June, 2016