You don’t want to die. If you heard that an asteroid would soon destroy a vast area around your home, you’d pay great costs to help you and your loved ones try to move. Even if you’d probably fail, even of most of your loved ones might not make it, and even if success meant adapting to a strange world far from home. If that’s not you, then this post isn’t for you.

Okay, you think you don’t want to die. But what exactly does that mean?

“You” are the time sequence of mental states that results from a certain large signal processing system: your “brain.” Each small part in this system takes signals in from other parts, changes its local state in response, and then sends signals out to other parts. At the border of this system, signals come in from “sensors”, e.g., eyes, and are sent out to “actuators”, e.g., hands.

You have differing mental states when these signals are different, and you live only as long as these signals keep moving. As best we can tell, from all the evidence we’ve ever seen, when these signals stop, you stop. When they stop for good, you die. As your brain is made out of completely ordinary materials undergoing quite well understood physical processes, all that’s left to be you is the pattern of your brain signals. That’s you; when that stops, you stop. (So yes, patterns feel.)

This signal processing system that produces you happens to be an organ of a particular complex multi-cellular animal: a “human”. This animal keeps working as long as all its organs keep providing their functions to each other. Your brain provides the function of monitoring and controlling high level decisions in this animal. Other organs provide functions like structure (bones), force (muscles), resource and waste distribution (blood), gas intake and disposal (lungs), light to signal conversion (eyes), and so on.

Given peace and prosperity, thankfully the norm for us today, the death of a multi-cellular animal like you typically results from the worn-down failure of just as one key part in one key organ, usually not the brain. At that moment of death, all the other organs, and all other parts of that failing organ, are still working acceptably. Unlike the artificial systems that we make today, natural animal systems usually can’t deal with broken parts by swapping in identical replacements from large stockpiles.

If you lived like most animals, you’d have to rely almost completely on the natural abilities of your organs to repair failing parts and to use redundant parts to replace failing ones. However, you, lucky you, are part of an advanced technical civilization, which offers many additional ways to help prevent and fix organ failures. For example, we can sometimes artificially clean out parasites and random garbage that gets in the way.

And at other times, we can substitute artificial parts and systems to replace failing natural organs. For example, we can ingest chemicals made in factories when our organs fail to make those chemicals. We have made artificial bones to give structure, artificial lungs to exchange gas, artificial hearts to pump blood, and so on. We’ve even made artificial extensions of some signal systems, such as artificial eyes and ears and artificial limb controllers.

Of course there are many organs for which we have not yet made artificial substitutes. But progress is rapid, and we have great reason for hope in the long run. Our civilization has come very far in a relatively short time, and it is quite reasonable to hope that within a few thousand years at most our descendants will have vastly greater capabilities. There’s no good reason to think we can’t eventually make artificial substitutes for all human organ systems. Yes, our civilization might destroy itself, or halt its growth, but there’s a good chance we won’t.

Now you might wonder: how is it even possible for us today to create artificial substitutes for natural organs? After all, our bodies are incredibly complex and detailed on atomic scales, yet we stand meters tall. If our artificial substitutes had to have a complexity that matched our existing complexity in fine detail over the entire scale of our bodies, then to design artificial organs we’d need to understand and design systems of a complexity vastly beyond anything we have ever managed.

What saves us is modularity. Evolution also had a limited ability to handle design complexity. So it used a modular system design. When there are only a few key organs systems, and when each organ system provides only a few main functions, then design variations within each organ can focus on how they effect the key functions of that organ, and mostly ignore other functions. And that means that our artificial design efforts can also focus mainly on how our replacements effect those key functions.

In addition, there’s the key fact that we are multi-cellular animals. Long ago, evolution spent a very long time honing single-celled creatures to survive and thrive on their own in the wild. Those designs became very subtle and efficient, but after a while because also hard to greatly change. When ecological niches opened up later for much larger organisms, evolution couldn’t be bothered to redo single cell type designs for much larger scales. That would require re-thinking many issues through nearly from scratch. Evolution instead just pasted many small cells together to make large organisms. So now each of our organs is mostly made up of many small cells pasted together.

In our organs, each cell is modified only a bit to allow it to serve its key function of allowing its organ system to provide its key functions. The vast majority of the complexity of each cell is mostly left alone. This is enormously wasteful in the sense that most of that cell complexity isn’t actually very useful in helping that cell to do what it needs to as part of that organ. But evolution found it easier to mostly just leave that cell package alone, rather than to try to greatly redesign cells for their roles in differing body systems.

The net result is that our bodies, and our organs, are actually much simpler than all that atom-scale complexity suggests. (Not simple of course, but simpler.) Which is why we can often design artificial replacements for key organs, to let us live longer before the failure of some part of an organ keeps our whole body from working, and thus killing the brain which produces the sequence of mental statues which is you.

Consider now the possibility of an artificial replacement for the brain organ. If we could make a work-alike for the brain, we might put it into a natural body, to prevent brain failures from killing that whole body. But if the main thing you really care about is your brain, where you live, then a much more dramatic anti-dying solution presents itself: replacing all the other body organs with artificial versions. Once you can make an artificial brain, that’s actually much easier than replacing one organ at a time. With artificial eyes, ears, muscles, energy sources, etc. we might make artificial bodies that can last as long as our artificial machines do today: indefinitely.

Today we can keep large complex systems like cars and buildings working indefinitely, by replacing parts as they break. Of course we don’t always do that, as we often find it cheaper to toss old systems and make new systems from scratch. We can even keep very complex computer systems working indefinitely, by making archive copies of files, and moving files to new computers as old ones die or become obsolete. With artificial bodies, we might similarly keep your mind going via replacing other body parts and swapping your mind to new brain hardware as needed. Not forever, but plausibly a lot longer than the current limit of roughly a subjective century.

So what are the prospects for making artificial brains? Unless brains are quite strange compared to other organs, we expect that most of the complexity in each brain cell is not very relevant for the function that cell provides the rest of the brain. Evolution searched for and found modest modifications of existing cell designs, modifications which let cells provide their key brain functions: sending signals to each other, and storing internal states that change in response to those signals.

When humans have designed signal processing systems, we have usually tried hard to insulate (in signal terms) the degrees of freedom in such systems that represent signals and states from all the other physical degrees of freedom in those systems. For example, in electronics we have wires and devices separated by insulators. It makes sense for evolution to also try this, for similar design reasons.

So when we find some signals and states in the brain, we should be able follow them to other strongly connected signals and states, and mostly ignore the much larger and more complex relatively isolated nearby parts of the system. This is like following the wires in a piece of electronics, allowing one to ignore all the parts of the system not collected by something like wires to the wired parts. This strategy usually works great for electronics, and when applied to our bodies has already enabled us to create artificial eyes and ears.

So far, we have started in on this wire-tracing task regarding brains, but are far from having finished. In fact, completion may take a century or more. We can clearly see some signals and states, and have traced them to some others, but have not obviously found them all, nor worked out all the local transformation mappings that map incoming signals to changed states and outgoing signals.

Thus it seems reasonable to expect that we will eventually be able to “follow the wires”, and figure out where human brains store their signals and states relevant for brain functions, and learn (to a sufficient accuracy) the signal-state-signal transformation mappings for all the different parts of the brain. Knowing this could enable us to scan a particular functioning human brain, seeing which kinds of cells are where connected to what, and create a work-alike of that particular brain in artificial hardware. If that was your brain, with your signal patterns, then then new artificial brain would be you as well. (And perhaps the only you remaining if the scanning process destroyed your original brain.)

Once you were in an artificial brain, how long til you died would become an economic question, not a biological one. You could live for as long as you could afford new replacement parts, and remained part of a civilization available to sell you such parts, and to protect you from predation. To someone like you, who doesn’t want to die, that should seem a very intriguing prospect.

Furthermore, the facts that you are a multi-cellular animal with a body design based on modular organs suggests that this isn’t some distant future in billions of years after inconceivable growth; it could happen in the next few centuries. Brains are probably more complex than the other organs for which we have already created artificial substitutes, but not fantastically more complex. So the fact that we have created many artificial organs in the last century or so suggests we might we make artificial brains within a few centuries.

Of course the obvious problem for you today is that we don’t know how to make artificial brains today, and your existing body will probably fail well before the centuries it may take to figure out how to make artificial brains. So how does any of this help you not die soon?

Well, consider the fact that we’ve seen cold people where all the usual apparent brain activity has stopped, and yet they revived just fine when warmed up soon afterward. This tells us that the brain scans that will be needed to create artificial brains can mostly ignore contributions to temporary brain activity. Scans just need to see the more permanent structures that channel temporary activity.

And that raises this key question: does the relevant info that a brain scan will need to see you in your brain, to allow the creation of an artificial brain holding you, does this key info survive the process of freezing your brain down to liquid nitrogen temperatures? At those temperatures, your brain is solid, and basically doesn’t change, for many centuries at least. So if the key info that specifies you survived that freezing process, why then we might freeze you now, keep you frozen for a long time, and then later when we know how to make artificial brains we could scan your frozen brain, grab that key info, and then make a new you in an artificial brain! That’s the relation between all this and your not dying.

Yes, it would cost some money to freeze you soon, to store you for centuries, and then to revive you later. Someone will have to pay for all that. And many things can go wrong over such timescales. Whatever contracts and organizations you support to enable this plan may fail. And even with success you’d come back to a strange different world, one that may lack many people you love. But the costs and risks would come way down if many people wanted this, and you said you are a person who wants to live, even if the chances are low and you’d have to live in a strange world.

We’ll talk more about these social issues in a bit, but before that we should engage this key info question: does the info that specifies you survive freezing your brain? We are pretty sure that the info that specifies you is there in your brain right now, encoded in the spatial patterns of densities of certain chemicals. (That is, we are pretty sure the needed info is not in orientations, spins, electric currents, magnetic fields, etc.) Perhaps many chemicals, though a tiny fraction of all the chemicals in your brain. So if we could suddenly and instantly freeze your brain, keeping all the chemicals in the same place, so that nothing moved afterward, then we’d be pretty sure to have saved the key info.

Unfortunately, changes do happen during the available freezing processes. Some unusual chemical reactions occur, and some things move around. However, we have many reasons to believe that enough info can be saved for it to be extractable from a frozen brain at a reasonable cost. Yes, in principle all info is saved in the universe, and could be regained by a powerful enough entity that could inspect the entire universe in great detail. But we don’t want to pin our hopes on such an extreme and unlikely-looking solution.

When we use our best current freezing tech, and then look via powerful microscopes at post-freezing tissues, most everything seems to be nearly the same, in nearly the same place. Also, we expect a lot of redundancy in brain design and encoding. We know that our organs are designed to function with great randomness in their detailed construction process. We seem to see a lot of redundancy in brain encoding, and know that the brain still functions under many big modifications, such as being whacked in the head or flooded with new chemicals. And we know that a modest rate of errors that require best-guess interpolation to fix seems tolerable; many things now change who we are over the decades, yet we still see ourselves as the same person enough to be worth preserving.

Okay, so it seems there’s a good chance that artificial brains will be possible within a few centuries, and so if we use our best current tech to freeze you today, and store that frozen brain for centuries, then future folks could make an artificial brain of you, and thus something close enough to you could be revived and live in that future world. Given that you don’t want to die, this plan should seem attractive to you.

Not just you, many millions like you. Sure, people vary in how much they don’t want to die, and in their beliefs on future tech progress and brain info freezing damage. But given what people say about how much they value life, a great many should find this attractive. At a typical value of life of five million dollars, then if this plan cost $50 thousand then only a 1% chance of success should be enough to make it seem worthwhile. Or if a strange future life was only worth a fifth of an ordinary life today, then a 5% chance of success should be enough.

Amazingly, a way to freeze your body when medicine gives up on you, and to preserve this frozen body for centuries with at least this chance of success, has been available at near this price for over six decades. Yet even though this option has regularly received free international publicity during this period, only about 3000 people have ever signed up for it, and only about 300 people have ever been frozen. Why so little interest?

One possible explanation is that this “cryonics” option has usually been framed around about a more ambitious plan: the full repair of your ordinary biological body, including all the damage done by freezing, and including the growing of a replacement body if they froze only your brain. While such full repair will probably be feasible eventually, this task seems much harder than creating an artificial brain and body. This really does require handling all the complexity of meter-scale and atomic-scale-detailed bodies, at least for the purpose of identifying failures and repairing them.

I’ve thought a lot about what life would look like given artificial brains, and in fact have written a whole book on it: The Age of Em. Since the artificial brain option seems to me better, and should be available much earlier, that’s the option I’d prefer. Even so, I don’t think we can explain very much of the lack of interest in cryonics in terms of this option being less highlighted so far. The full repair option isn’t crazy, and should still be attractive to people who don’t want to die.

In my other book, The Elephant in the Brain, I explain how we humans are often wrong about our motives. In particular, regarding medicine we think we care about health, yet we actually mainly care about showing that we care about others, and letting them show they care about us. As a result, far more of us actually die faster than we would under a system that was actually driven mainly by a concern for not dying. And yes that probably applies to you as well; you will probably die sooner than you would if your attitude toward medicine were driven mainly by your not wanting to die.

Perhaps your conscious mind is now screaming “No, that’s not me, I really don’t want to die.” But those thoughts aren’t very honest. They might feel sincere, but they aren’t integrated into a whole mental system that actually works that way. When thoughts of death come to your mind, your mind freezes and goes crazy just like everyone else’s, and can’t think death threats through very carefully. You also tell yourself that on something this important you don’t care much what others think, and you’d do whatever it takes even in the face of criticism and conformity pressures. But if your plan to not die faces strong opposition from loved ones, you’ll usually cave.

Regarding the option to not die that I’ve been discussing here, freezing to await artificial brains, your mind has either latched on to some lame excuse why this plan is infeasible or uninteresting, or you’ve told yourself yeah you do want to do this, and you’ll make a vague plan to do so, but you won’t actually do it. Perhaps your loved ones will object, and you’ll cave. Remember: a significant fraction of folks who hear about cryonics plan to sign up, but almost none ever do. (Amazingly, a similar number of people pay a similar amount to have their remains burned and their ashes thrown into space, an option produces far less hostility from loved ones.)

Perhaps your mind is still screaming “No, that’s not me, I control my plans, and I don’t want to die!” Well then, go ahead, prove me wrong, and join the 3000. Make me proud of you. (That 3000 is only 10% of my Twitter followers; if I could double that number to 6000, I’d consider my life well spent.)

Is your doubt of the form, “But isn’t this selfish of me, to spend money on my not dying?” Note that we all supposedly spend lots on ourselves via medicine to not die. And as this cryonics product is dominated by fixed costs, the more who sign up to be frozen, the cheaper and more reliable this product can become.

This product happens to be unpopular now, but no law of nature requires this. If we could switch to a new social equilibrium where people used cryonics to show that they care, then at a quite modest cost most everyone who is alive today need not die! Isn’t that a noble altruistic cause worth fighting for?

Look, large surveys show that the main reason people actually reject artificial brains is because they seem “unnatural”, the same reason people rejected IVF before that was possible, and yet now widely accept it:

People who value purity norms and have higher sexual disgust sensitivity are more inclined to condemn mind upload. Furthermore, people who are anxious about death and condemn suicidal acts were more accepting of mind upload. Finally, higher science fiction literacy and/or hobbyism strongly predicted approval of mind upload.

Whatever reasons you think you have in your head are mainly excuses for these factors. Will you really let yourself die because a purity norm now makes a thing as yet unseen seem unnatural to you?

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