No human has ever been revived from cryopreservation. With today's technology, no one can be.
That is the most important sentence on this page. Every honest argument for cryonics is built on top of it rather than around it.
Four locks, not one
"We cannot revive anyone yet" sounds like a single obstacle. It is four, and they fail for different reasons.
The cause of death is still there
Preservation begins at legal death, so a patient arrives with whatever killed them unrepaired. Advanced cancer, organ failure, the damage of a stroke.
Revival is not warming someone up. It requires curing the condition that ended their life, and for most causes today's medicine cannot do that even in a living patient.
This lock is not special to cryonics. It is the ordinary frontier of medicine, and it may well be opened by people who never thought about preservation at all.
The preservation itself leaves damage
Some ischemic injury accumulates before cooling, as the race against cellular decay describes. Vitrification is good and is not perfect.
Reversing that needs repair at cellular and molecular scale. Those tools do not exist, and what they would have to do is set out in can patients be revived without defects.
Rewarming has no solution at human scale
The cryoprotectants are harmless while everything is paused in the cold, and toxic once warm.
A body would have to warm through the danger zone without ice forming, then have the agents washed out before they act. The technical article covers why that is so hard.
We cannot read a connectome, let alone restore one
The bet is that identity lives in brain structure, the connectome described in memory, identity and the brain.
Grant that the structure survives. We still have no way to map a whole human brain at the resolution required, and no way to restore function from such a map.
The resolution demanded is severe. Synapses are tens of nanometers across, far below anything a clinical scanner resolves.
Current mapping is also destructive. Tissue is sliced and imaged, which yields a map and consumes the original, and that trade is acceptable for research and not for a patient.
Why "not yet" is a different claim from "never"
Those four locks share a property worth noticing. None of them requires breaking a law of physics.
They are engineering problems of extraordinary difficulty. That is a different category from perpetual motion, and the difference carries the whole argument.
It is also not a promise. Plenty of engineering problems stay unsolved for centuries, and some turn out to be harder than they first looked.
The distinction changes how any claim in this field should be read, including ours. A claim that something is physically impossible can be settled with an argument.
A claim that something is merely very hard cannot. It gets settled by decades of work, or by the work failing, and neither is available in advance.
The candidate routes are laid out in how we might achieve revival, and the most demanding of them rests on the nanotechnology bet.
Anyone telling you the timeline is knowable is guessing, which is why we treat timing with so much caution.
What can be said is narrower and more useful. Preservation cannot promise revival. It can keep open a door that burial and cremation close permanently.
That is the lopsided arithmetic of a small chance against none, and it needs no optimism about dates.
What would count as progress
Vague hope is not evidence. If the four locks are real, progress means specific locks opening at specific scales.
Whole-organ round trips are the first marker. A rabbit kidney has been vitrified, rewarmed and transplanted, and in 2023 rat kidneys were recovered the same way and kept their recipients alive.
Functional recovery of brain tissue after vitrification is the second, and the current papers are collected in relevant research papers.
Connectome mapping is the third. Progress there is measured in the volume of brain reconstructed, and that volume is currently cubic millimeters.
Watch those three numbers over the next decade. They will tell you more about revival than any confident prediction can.
Each marker opens a different lock. An organ round trip says nothing about connectomes, and a connectome map says nothing about rewarming.
Movement on all four at once is what a real path to revival would look like. Movement on one is a good year for a research group.
The work aimed at them is described in advancing the field and our research and development initiatives.
None of it makes revival likely today. All of it moves the problem from impossible toward hard, which is the only direction that matters.
Why we say this out loud
Stating all this plainly looks like undercutting our own case. It is the opposite.
Cryonics is only defensible when sold for what it is. The claim is not that we will revive you.
The claim is that we will preserve the structure that is you, as well as circumstances allow, so a future medicine has something to work with if it ever can.
A provider who blurs that line is doing the thing critics accuse the field of doing, and the accusation is examined in is this a scam.
It also changes what a member is agreeing to. You sign up for a preserved chance rather than a scheduled return, and informed consent means understanding exactly that.
There is a practical test for any provider's honesty here. Ask what they expect will not work, and see whether the answer is specific.
The strongest version of the case survives this honesty. If it did not, it would not be worth making.
TL;DR: Human revival is impossible today because we cannot safely rewarm, repair and restore a cryopreserved person. Cryonics preserves a possibility for future medicine, not a scheduled return.
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