Thought experiments as knowledge

One of the most remarkable aspects about the ongoing debates concerning the technical feasibility of mind uploading is the excessive confidence that some people have that these issues can be resolved without further experimental validation. The (implicit) assumption seems to be that our current understanding of the neuroscience of consciousness is sufficient to demonstrate the technical feasibility of mind uploading by logical deduction from these findings alone. This is a mysterious claim for at least two reasons. The most fundamental reason is that the scientific study of consciousness has not nearly evolved to a stage that allows for making bold claims about the subject, let alone its far-reaching consequences. The other reason is that, in the absence of empirical examples of substrate-independent life in general, it cannot be argued that such logical arguments are just innocent or inescapable conclusions from what we already do know.

It should not be surprising that such arguments fail to convince some of the participants in the debate. After all, many “mind uploaders” also believe that the case for cryonics is just a straightforward exercise of Pascal’s Wager and the technical feasibility of molecular nanotechnology can be settled by arguing that the idea does not “contradict the laws of physics.” As I have argued in a more detailed article about this tendency, the common denominator in all of  this is the excessive role that is assigned to logical arguments (or rationalism). But there is an important difference between, let’s say, predicting the unmeasured viscosity of a specific aqueous solution from a formula that has been derived from numerous measurements on the one hand and drawing far-reaching conclusions from general scientific observations or even philosophical premises (materialism, reductionism) on the other hand.  This does not mean that one should completely refrain from speculation about future technologies, but it should induce a habit of having less confidence in your conclusions as the chain of assumptions and logical arguments lengthens, let alone if your conclusions are highly controversial.

One could object that since advocates of mind uploading are generally strong advocates of cryonics, that even treating their arguments with skepticism risks alienating prospective supporters of cryonics. The fact of the matter is, however, that presenting cryonics as just one element in a larger futurist framework strongly weakens the point that cryonics is an experimental medical procedure, not an ideology or life-style. It is not possible to present cryonics in a fashion that does not alienate anyone at all. But presenting cryonics as an experimental medical procedure without additional ideological, philosophical, or sociological add-ons  has the important merit of reducing this amount of alienation to the greatest possible degree. It also has the distinct advantage that it facilitates the recruitment of people who can move the field forward; experimental scientists and medical professionals.

Mind uploading, falsifiability and cryonics

On the cryonics discussion list Cryonet cryobiologist Brian Wowk weighed in on the topic of mind uploading in a post that merits quoting in its entirety:

I read with interest Bob Ettinger’s recent remarks about Mark Gubrud’s piece in The New Atlantis.

Although I have not been around as long Bob, I have nevertheless observed arguments about uploading, identity duplication, and related subjects for decades.  In all that time there are two things I’ve never seen: (a) A truly new argument, and (b) Someone change their mind.  What is seen are people who passionately believe they are correct, and who believe that they have just the argument to finally convince the other side that they are right.  They never do.

I have come to believe that the question of whether a computationally equivalent duplicate of a human mind (assuming equivalence in this context is even definable) constitutes a continuation of the original person may be objectively unanswerable.  It’s almost a matter of taste, like alternative interpretations of quantum mechanics that assume different underlying realities that give exactly the same measurable results.

Eventually the distant day will come when the computational processes of a human brain are duplicated in an electronic computer, or even in another identical organic substrate.  When that day comes, we can be certain of this: If the person who was “duplicated” believed before duplication that duplication constitutes survival of the self, then, by definition, the duplicated entity will insist vociferously that indeed they did survive.  This has ethical implications.  Conversely,
an entity derived from a person who did not believe in this form of survival might be quite unhappy to be told that they were the product of a destructive scan of somebody.  This too has ethical implications.

Philosophical truth aside, evolution selects against humans who spend time worrying about whether sleep, anesthesia, or biostasis endangers personal identity.  Similarly, it is easy to predict which side of the uploading and duplication debates will win in the long term.  There is no entity more invulnerable or fecund than one that believes it consists of information.

Recent discussions of the topic of mind uploading on the Cryonics Institute members mailing-list contradict Wowk’s claim about people changing their mind about mind uploading. Robert Ettinger posted an itemized list with objections against the idea of mind uploading as a strategy for personal survival and I weighed in on the (current) lack of experimental evidence to settle the matter. The effect was that some people changed their mind or became more agnostic about mind uploading.

Wowk may be correct that the question whether a “computationally equivalent duplicate of a human mind…constitutes a continuation of the original person may be objectively unanswerable.” The discussion about mind uploading and persistence of the original person has distinct similarities with discussions about solipsism, consciousness, and the existence of the external world. It is not inconceivable that in a world where mind uploading has become routine the debates will still continue because the hard problem of persistence of the person is not falsifiable in a meaningful manner.

There are mind uploaders and there are Mind Uploaders. The Mind Uploaders are a small but vocal minority who display little patience for the argument that the technical feasibility of mind uploading requires empirical verification and cannot be completely settled by logical deduction or thought experiments. As cryonics activist and ex-Alcor Board member David Pizer says, “Having existed with Uploading Lovers for many years now, I believe they are as firmly entrenched in their beliefs as  traditional religious persons believe that their souls are going to Heaven after death here on Earth.”

Cryonics is often associated with ideas like mind uploading and transhumanism. One negative consequence of this (un)intentional association is that some people who are considering cryonics feel that they have to embrace a much larger set of controversial ideas than what they are actually being asked to consider. As a result, there is a real risk that people reject cryonics for reasons that have little to do with the proposal of cryonics itself. Advocates of cryonics do not do themselves a favor by promoting the idea of human cryopreservation as part of a larger set of futurist ideas instead of just promoting cryonics as an experimental medical procedure to extend life. There is too much at stake to alienate people by piling more controversial ideas on top of what is already considered to be a radical idea. Such a low-key attitude will also produce a more consistent message because it extends the element of uncertainty that is inherent in cryonics to other areas of life as well.

David J. Chalmers on the Singularity, mind uploading and cryonics

If I would make an argument in favor of mind uploading (or substrate independent minds) it would not be a logical deduction from what we know about neuroscience but from what we don’t know.  As one of the leading philosophers of mind David J. Chalmers has argued in this insightful paper about the Singularity and mind uploading:

Can an upload be conscious? The issue here is complicated by the fact that our understanding of consciousness is so poor. No-one knows just why or how brain processes give rise to consciousness. Neuroscience is gradually discovering various neural correlates of consciousness, but this research program largely takes the existence of consciousness for granted. There is nothing even approaching an orthodox theory of why there is consciousness in the first place. Correspondingly, there is nothing even approaching an orthodox theory of what sorts of systems can be conscious and what systems cannot be….

It is true that we have no idea how a nonbiological system, such as a silicon computational system, could be conscious. But the fact is that we also have no idea how a biological system, such as a neural system, could be conscious. The gap is just as wide in both cases. And we do not know of any principled di differences between biological and nonbiological systems that suggest that the former can be conscious and the latter cannot. In the absence of such principled di differences, I think the default attitude should be that both biological and nonbiological systems can be conscious

One can argue with this derivation of what the “default position” should be, but his more skeptical approach has a degree of modesty in its favor that is often lacking in transhumanist circles.

David J. Chalmers also discusses cryonics in a favorable context:

Cryonic technology off ers the possibility of preserving our brains in a low-temperature state shortly after death, until such time as the technology is available to reactivate the brain or perhaps to upload the information in it. Of course much information may be lost in death, and at the moment, we do not know whether cryonics preserves information sufficient to reactivate or reconstruct anything akin to a functional isomorph of the original. But one can at least hope that after an intelligence explosion, extraordinary technology might be possible here

On his blog he also writes that “for the last couple of weeks I have been in Oxford giving the John Locke Lectures on Constructing the World.  The title is an homage to Rudolf Carnap’s 1928 book Der Logische Aufbau Der Welt. The lectures are based on a book I have been writing for the last couple of years, trying to execute a project that is reminiscent of Carnap’s in certain respects.”

A person who discusses mind uploading in a meaningful context, gives cryonics a fair hearing, and has a work in progress that is inspired by Rudolf Carnap’s The Logical Structure of the World should not be ignored, let alone be ridiculed.

Down with uploading

Over the last couple of years, cryonics pioneer Robert Ettinger has been a vocal critic of simplistic defenses of the idea of mind uploading as a survival strategy. He has worked out his reservations in detail in his latest book Youniverse: Toward a Self-Centered Philosophy of Immortalism and Cryonics. In a recent CryoNet message he reiterates some of his basic arguments:

“Identity of indiscernibles” is a  common tenet. Often attributed to Leibniz, one  version is that if two physical objects or systems cannot be distinguished from  each other by any criterion, then they  must be considered the “same” or  identical. First, this assertion actually asserts nothing except a  certain preference in use  of language. It has no consequences. It is also useless because if the question arises, are A and B distinguishable, the answer  is always yes.

It is hard to see how anyone can claim complete certainty  on the topic of mind uploading. Nevertheless, to some of its more dogmatic advocates the case for mind uploading is simply an exercise in deductive reasoning. There are major objections to such an attitude. The most obvious point is general; why should mind uploading be an exception to the rule that we can have no certain knowledge? One might object that absolute certainty is possible in logic. But in that case one would need to defend the thesis that the feasibility of mind uploading (and its associated views about identity) is a purely logical matter and exempt from empirical testing. This is not a credible position.

This does not mean that questions about identity will be easily answered when such technologies are available. For all we know, mind uploading will be technically feasible and the debates about identity continue.  There is a lot of merit to discussions about mind uploading and identity, especially for those interested in cryonics and life extension. But there is also a lot to say for being modest in making bold claims before such technologies have materialized.

The science of personal survival

There are various competing strategies how to achieve meaningful life extension or rejuvenation, including , but not limited to, genetic manipulation, periodical elimination of damage, caloric restriction,  molecular nanotechnology and mind uploading. A useful review of these strategies has been published in the book The Scientific Conquest of Death: Essays on Infinite Lifespans (2004) by the Immortality Institute. Most people will recognize that these strategies are not mutually exclusive. Some of them can be practiced right now (e.g., caloric restriction) and others ( e.g., periodical elimination of damage) could serve as a bridge to more comprehensive interventions such as a comprehensive genetic overhaul of human biology. As has often been recognized on this website, cryonics holds a special place among life extension strategies because it enables one to benefit from progress in the biomedical sciences that may not occur during one’s lifetime. We would like to think we can escape death by jumping from one successful biomedical innovation to another and that, of course, all the good things will happen in our lifetime, but reality often interferes with such optimism.

One thing that might greatly accelerate the pace of progress in the field of longevity science is the development of an integrated framework that studies the logical and empirical relationships among all these strategies. For example, a recent blog entry on the technical challenges surrounding chemopreservation of the brain triggered a meaningful private exchange about issues concerning the perfusion of ischemic tissue, empirical criteria for information-theoretic death, and the options for histological validation of cryonics technologies.  Such overlapping areas of investigation are plentiful and it would be helpful to explicate them.

Too much focus on “the big picture” can interfere with the identification of original ideas and rapid progress. Too little attention to the adverse effects of compartmentalization risks the waste of resources, which is not a trivial concern in the still poorly funded life extension community.

Reducing compartmentalization can have other sobering effects as well. For example, it is not unusual to see a group of researchers advocating a new approach to their field that is routine in other areas of investigation. For example, the idea that anti-aging research could benefit from less emphasis on illuminating the exact molecular mechanisms of aging and simply treat the observable manifestations of aging is no news to researchers in the field of cerebral ischemia. The pathophysiology of stroke is so complex that greater progress could be achieved by identifying clear targets for pharmacological intervention. But after decades of research it has become abundantly clear that such a paradigm change is no guarantee for more rapid progress. Despite this goal-oriented approach not one single neuroprotective agent has survived clinical trials.  This does not mean that such pragmatic approaches should be abandoned. It does mean, however, that research ideas should be evaluated on their empirical success and not just on their logical merits.

There are obvious examples where the claims in one field seem to make the claims in another field redundant. The most obvious example is the case of molecular nanotechnology. The projected timescales that are envisioned for this technology are not much different from the timescales that are envisioned by some anti-aging researchers to develop meaningful rejuvenation. In that case one could argue that (exclusive) preference should be given to those research programs that allow for the most comprehensive manipulation of biology. For example, a mature nanotechnology would be able to rejuvenate people, resuscitate cryonics patients, and alter the human endoskeleton to make us far less prone to fatal accidents. Such an argument would be a logical extension of the argument against devoting too much time to find treatments for specific age-related diseases instead of tackling aging itself.  Similar reasoning can be employed against anti-aging research. If accelerated change will bring the prospect of general molecular control within reach in the next few decades it makes little sense to spend vast amounts of time agonizing over specific anti-aging interventions. Why not just launch a “Manhattan Project” to pursue the much more comprehensive vision of molecular nanotechnology?

From a logical point of view, this is a persuasive argument. The limitations of such a perspective should now be obvious too.  We do not have certainty about the future of technological progress, let alone its specifics. As a matter of fact, in such matters it is not even evident how we should think about statistical or inductive probabilities.  To some people, the progress in one field is indicative of the progress we are going to observe in other fields, including fields in which there has been little progress to date. The problem with such naive inductivism is that it can just as well be used to  make the opposite case if a different reference class is chosen.

The logical empiricist philosopher Rudolf Carnap once wrote:

The acceptance or rejection of abstract linguistic forms, just as the acceptance or rejection of any other linguistic forms in any branch of science, will finally be decided by their efficiency as instruments, the ratio of the results achieved to the amount and complexity of the efforts required. To decree dogmatic prohibitions of certain linguistic forms instead of testing them by their success or failure in practical use, is worse than futile; it is positively harmful because it may obstruct scientific progress.

A related argument can be made about the science of personal survival. We should be cautious about privileging any line of research on  “logical” grounds. The fate of competing visions should be decided through empirical investigation.  This position should not be interpreted as saying that there is no place for logic in choosing research programs.  Logic has a central place in research design and interpretation of experimental observation but it cannot be solely relied upon a guide for decision making. Empirical observation disciplines thinking and ample room should be left for the unexpected. As Nassim Nicholas Taleb has pointed out:

There is a lot more randomness in biotechnology and any form of medical discovery. The role of design is overestimated. Every time we plan on trying to find a drug we don’t because it closes our mind. How are we discovering drugs? From the side-effects of other drugs.

Many experimental researchers have had the experience of engaging in research to find a solution to one problem but to discover the solution to another problem instead. Researchers who have recognized and embraced this phenomenon by becoming less fond of their own ideas and more open to run with such unexpected discoveries have reaped great benefits.

Brain preservation

Mind uploading advocate Kenneth Hayworth has launched an interesting website devoted to the science of brain preservation. Of particular interest is his Proposal for a Brain Preservation Technology Prize (PDF). This document includes one of the most comprehensive discussions of chemopreservation as a strategy for personal survival. For example, one of the most common objections to chemopreservation is that fixatives like formaldehyde and glutaraldehyde do a poor job of fixing lipids. In this document, Hayworth reviews a number of papers where a fixative that can stabilize lipids, osmium tetroxide, is perfused (!) through the circulatory system.   For human sized brains such a step would be necessary to avoid the ischemic damage and autolysis that would occur in the case of the time-consuming alternative of diffusion fixation.  He also speculates that such a fixed brain can be perfused with a high viscosity plastic resin for long term preservation.

One of the limitations of this approach, as the author concedes, is that the procedure needs to be started before death. In reality, the situation is even more challenging  than that because the procedure would have to be started before ischemia-induced brain perfusion abnormalities associated with terminal disease and the agonal phase will manifest themselves. This is a problem where “old fashioned” cryonics has a clear advantage. Perfusion impairment may interfere with complete distribution and equilibration of the cryoprotectant in the brain but the unperfused tissues will still be stabilized (although in a damaged form) through low temperatures. In the case of chemical fixation such a “second chance” is absent. This is not just a theoretical problem. Cryonics researchers have become painfully aware of the adverse effects of even the slightest perfusion artifacts on the quality of fixation and the resulting electron micrographs.

As a consequence, this kind of “high quality” chemopreservation can only be a credible alternative for cryonics if the medical establishment would permit the procedure for those who are diagnosed as terminally ill. If the acceptance of cryonics is any guidance, there is little chance that this will happen any time soon.

Chemopreservation has another major obstacle to deal with. As the cryobiologist Brain Wowk has stated on numerous occasions, chemical fixation is a dead end in terms of reversibility with contemporary technologies. This aspect of chemical fixation limits the demonstration of its technical feasibility to a demonstration of ultrastructural preservation.  In the case of cryonics, evidence of excellent ultrastructural preservation has produced little excitement among the scientific establishment and the general public. Linking chemopreservation exclusively to mind uploading may present another obstacle to its acceptance.

In his essay Killed by Bad Philosophy: Why brain preservation followed by mind uploading is a cure for death [PDF] Kenneth Hayworth attempts a defense of mind uploading by identifying the philosophical errors that those who reject the concept, and those who argue that “a copy is not you” in particular, engage in. The author shows little doubt about his position although one might object that the central example that is used to make the case could also be used to  argue against mind uploading. One might even object  that the whole debate involves a pseudo-problem if any kind of empirical observation can be made consistent with the case for and the case against mind uploading.

Aside from these complexities, this is an admirable effort to raises interest in high quality brain fixation. Initial funding for more experimental research should be encouraged.

Cryonics as something else

At EconLog economist Bryan Caplan has posted a number of blog entries that perfectly illustrate what happens when cryonics is not presented as a form of experimental long term critical care medicine but linked to other ideas such as transhumanism, mind uploading, and immortalism. One post is titled “What’s Really Wrong With Cryonics” but a close reading of the post and subsequent exchanges between Caplan and cryonics advocate Robin Hanson leave little doubt that this exchange is really about the technical feasibility of mind uploading and the nature of identity.

These topics are of great philosophical and practical interest to some but have little relevance to the technical feasibility of cryonics. When a person goes in for surgery it is not common to engage medical personnel in abstract arguments about the nature of identity prior to induction of anesthesia. Similarly, when hypothermia is used to allow complete circulatory arrest in complex surgical brain procedures it is not common to object that this procedure puts the soul at risk. Even people who do not subscribe to the  empiricist premise that underpins modern medicine have come to accept the procedures that are associated with it. Cryonics, as conceived and practiced by organizations like Alcor, is just an extension of the idea that metabolism can be reduced or stopped without inevitable irreversible death.

It is therefore surprising how many discussions about cryonics actually deal with “something else”: overpopulation, transhumanism, the Singularity, egoism, religion etc.  It would be convenient to put most of the blame on people who do not want to seriously engage with the technical and bio-ethical arguments involving cryonics but there is an undeniable tendency of some cryonics advocates to dwell excessively on the issues that triggered their own interest in cryonics or alternative methods to preserve one’s identity.  There is nothing forbidding cryonics to be linked to such topics but in light of the fact that cryonics as understood by the average person faces formidable obstacles of its own, it is not good public relations to link what is essentially a logical development within medicine to speculative futurism.

Bryan observes that he’d like to think “that Robin’s an outlier among cryonics advocates, but in my experience, he’s perfectly typical.  Fascination with technology crowds out not just philosophy of mind, but common sense.” We have made similar claims on this website but with the purpose to advance the cause of cryonics. Bryan is dead-on regarding the issue of common sense, but it is the same common sense that compels one to conclude that philosophy of mind has little practical relevance to biomedical research and practice. Unless Bryan can make a persuasive case that lowering the temperature of a patient to +20 degrees C raises no philosophical issues but lowering the temperature to -196 degrees C does raise philosophical issues there is no reason to introduce such issues into debates about the technical feasibility of cryonics.

DNA preservation and cryonics

pyreneanibexFollowing the news that mice have been cloned from 16 year old frozen tissue comes an announcement that scientists have made advances in resurrecting  the extinct Pyrenean Ibex. This does not only offer hope that someday other extinct species may be resurrected and returned to nature, it further reinforces the power of low temperatures to preserve life and biological information.  DNA can be extracted from tissue that is preserved with crude  freezing techniques, including cryopreservation with no cryoprotection at all (straight freezing).

Successful resuscitation of cryonics patients requires reversal of the aging process (for most patients) and  advanced molecular cell repair technologies. Such demanding requirements are not necessary to clone a cryonics patient. Although the objective of cryonics organizations is not to resurrect a clone of the person but that particular individual, the recent success stories about cloning animals from frozen tissue highlight that the debate about the feasibility of cryonics should not be so much about “revival” but personal survival.  Biological revival should not present major obstacles.

People usually do not make cryonics arrangements to allow a the creation of a genetic copy of themselves in the future. One use of human DNA storage is to assist with the identification of remains of cryonics patients that have died under circumstances where such identification will be difficult (for example, the cryonics organization only receives a brain). DNA preservation is also an option for people who would like to have a  closely similar pet in the future. Futuristic possibilities such as combination of human cloning and mind uploading to recreate the person come to mind as well.

The Cryonics Institute offers human and pet DNA preservation for members with and without funding arrangements.

Biostasis through chemopreservation

Twenty years ago, Charles B. Olson published an article called “A Possible Cure for Death” in the journal Medical Hypotheses. In it, he favorably compares methods of chemical preservation to cryogenic preservation. Unfortunately, this article provoked no wide discussion or attempts at implementation. As the author notes on his website, other than requests for reprints, “nothing more came of it.” And yet the arguments in it are still sound and just as persuasive today as they were then. Why the reluctance?

Freezing has a certain subjective appeal. We freeze foods and rewarm them to eat. We read stories about children who have fallen into ice cold water and survived for hours without breathing. We know that human sperm, eggs, and even embryos can be frozen and thawed without harm. Freezing seems intuitively reversible and complete. Perhaps this is why cryonics quickly attained, and has kept, its singular appeal for life extensionists.

By contrast, we tend to associate chemical preservation with processes that are particularly irreversible and inadequate. Corpses are embalmed to prevent decay for only a short time. Taxidermists make deceased animals look alive, although most of their body parts are missing or transformed. “Plastinated” cadavers are used to demonstrate surface anatomy in schools and museums. No wonder, then, that cryonicists routinely dismiss chemopreservation as a truly bad idea. Although from time to time chemopreservation is raised as a possible alternative to cryonics (Perry, page 21-24), to this day it has not been given the full consideration it deserves

Part of the confusion around chemopreservation concerns the quality of preservation that is possible with this method. Chemical methods of preservation such as fixation are not only adequate, they have long been the gold standard for biologists studying the structure of cells and the brain. As Olson notes,

The technological advances in the preparation of tissue for microscopy have directly improved the prospects of brain preservation for reanimation. This is not a coincidence: the goals of microscopy and brain preservation for reanimation are fundamentally similar. In both cases, a maximal amount of structural detail is preserved such that information can be extracted.

When fixed immediately and properly embedded in a solid medium, tissue can preserve physical structure indefinitely. The entire brain can begin to be fixed by arterial perfusion within minutes after pronouncement of death. Fixation can be done by hospital pathologists or funeral home specialists. The brain can then be impregnated with a solid-setting polymer so that it becomes fully inert.

But what of reversibility? Olson dismisses the need for reversibility. The information in the brain can be retrieved and run on a different substrate — a new organic or machine brain. However, K. Eric Drexler’s proposal in Engines of Creation, nanoscale mechanical repair, could also apply to chemopreserved brains just as to cryopreserved brains. The damage caused by fixation and embedding might be able to be reversed just as the damage caused by freezing or vitrification, if, in both cases, identity-critical information preserved in the brain has not been lost.

If personal identity is preserved in the brain in physical structures such as synaptic circuits, then we know that chemopreservation can preserve these structures just as well as cryopreservation. In fact, chemopreservation entirely avoids the danger of ice formation and fracturing, which in theory could destroy physical structures in the brain and cause irretrievable identity-critical information loss. While fixatives cause molecular changes in the brain, by crosslinking and denaturing proteins, cryoprotectants also cause chemical damage which must later be repaired. While it is not certain that chemopreservation can preserve all identity-critical information, it is also not certain that cryonics stabilization, cryoprotection, and vitrification preserve all identity-critical information.

For those who accept the method of resuscitation by scanning the brain and running it its processes on a different substrate (“mind uploading“), chemopreservation might present additional benefits. The chemopreserved brain, unlike the cryopreserved brain, is ideally suited to microscopic extraction of information:

The molecules in a chemopreserved brain have been extensively crosslinked and can be embedded in a plastic which was designed for electron microscopy. Consequently they will be resistant to the heat and damage generated by whatever beam of particles (or other investigative device) is used to determine the details of the internal structure. In contrast, a frozen brain is not particularly prepared to resist damage, and is acutely sensitive to any heat generated.

But even for those who prefer mechanical repair of the brain, chemopreservation presents benefits that cryopreservation does not.

First, it is potentially cheaper, because it does away with the need for expensive long-term care. Chemopreserved patients would not require labor to keep them in the same condition, other than storage in a secure, designated area, unlike cryopreserved patients who are in continual danger of thawing. Cryopreserved patients require continual monitoring of liquid nitrogen levels and topping off with more liquid nitrogen, as well as special, expensive containers that can hold liquid nitrogen, and these containers need regular maintenance, repair, and replacement. Liquid nitrogen also presents hazards that require continual air monitoring and alarms.

The basic techniques for chemopreserving a brain — fixation and polymer impregnation — would also not require the services of specially trained volunteers or professionals; they are routine techniques used in hospital pathology labs and departments of anatomy around the world. As Olson notes, “the cost of brain chemopreservation could be less than that of a typical funeral.”

People are routinely turned away from cryonics providers because they cannot afford cryopreservation. So what are we waiting for?