The Politics of Karl Popper — Part 5: David Deutsch, the Future and Infinity

Jed Lea-Henry
13 min readJun 21, 2019


The problem of how knowledge accumulates in the world — of how it is that we can know anything at all — is the most important lesson that our species could ever learn. The implications of this understanding reach into every field of study, into every improvement, into everything we do or could ever possibly do. And so understandably — for most of our history — it was also the philosophical problem that attracted the sharpest minds, the most intellectual energy, and which nagged most heavily upon us by our consistent failure to solve it.

And yet when Karl Popper did so, very few people paid any attention, and those who did showed a remarkable ability — despite the simplicity of his answer — to misunderstand him. Before Popper — despite the gap in our knowledge — everything felt a little more elegant, neat and high minded. It was all completely wrong, but it was also, quite consciously, a race to the top; or the bottom depending on your metaphor. People were searching for a foundation, the bedrock of who we are, and a place from where we could build ourselves up into giants. The impulse was noble, and yet entirely misguided — the only thing they were right about was the ‘giant’ part.

Instead of seeking to understand the foundation of knowledge, Popper showed instead that knowledge can’t possibly have one. A foundation to knowledge, is a claim that something is so incontrovertible that it cannot be challenged, because the very question ‘why is that the foundation and not something else?’ is a state of doubt, and a foundation is, by definition, an obvious truth. And it is only once you are certain about a foundation that you can then be certain about the truths you build upon it. Something that can be questioned, is something that isn’t certain.

This is a clean, neat and reductionary way of thinking about the problem of knowledge — it is also totalitarian, and doesn’t take into account the place in which we actually find ourselves, and what is actually available to us. Popper solved this problem by asking a different question — the correct question — and so showed that our interactions with the world, and even ourselves, is a theory-laden process; we never perceive anything as it actually is. Our senses and instincts always lead us astray, because unseen theories about reality (knowledge) don’t resemble what we see. We only come to true theories through long chains of conjecture. If knowledge came to us directly from the senses, then our theory about stars for example would still hold that they are small, cold, twinkling objects; rather than massive, hot spheres of nuclear explosions.

This difficult relationship that we have with reality, means that the natural state of things is error. We are wrong about everything, all the time. And when we do believe that something is true, it can never be said to be for certain; only that it is the best available theory that we currently have. Rather than a hierarchical order, where truth builds upon truth like bricks upon a steady and unchanging foundation, the process of knowledge creation is like being dropped blindfolded, in the middle of the night, into a vast and unfamiliar swamp. The mud immediately reaches your waist, and you have no idea what is the best direction to head for dry land. All you can do is take a tentative step forward in any one direction (conjecture), and once there make a judgement as to whether it feels better or worse than where you started from. If you judge it to be worse (refutation) — the water is deeper or the mud thicker — you don’t necessarily move back to where you began, but perhaps in a completely different direction that you feel (again conjecture) might be better than both. And so on.

Most unsettling about this, is the realisation that when you finally, and painstakingly, crisscross your way — after countless corrections — toward a path that feels like progress, you can still never be sure that you are actually heading in the right direction. The water may be getting shallower, the ground under your feet feeling more solid, the swarms of mosquitoes less thick and less aggressive, but that steady incline you are on might just be a small sandbar in an otherwise deeper and more inhospitable part of the swamp. Your next step takes you over its edge, and now with water above your head you are swimming desperately back the way you came (again refutation).

When your solution to a problem sounds like this, is it any wonder that people instinctively turn away? But this is the same instinct that causes people to turn away from democracy in favour of authoritarianism, to prefer the status quo to social progress, and to fear technology and the future — worst of all, to not appreciate the infinite reach of human beings.

David Deutsch — an Oxford physicist and the father of quantum computation — came to Karl Popper in the tragic way that most people do — by chance and accident. It was an off-hand comment by a university professor who, despite not quite understanding Popper, was aware that Popper had solved the problem of how knowledge accumulates in the world. Immediately recognising that he was dealing with a higher level of argument than what he had encountered before, that small poke sent Deutsch off in new directions. There were no fudges, no strains of reasoning; the world Popper drew a light on was messy, but his theory was clean-edged and exact.

Everything that Deutsch would do from this moment had the unmistakable echoes of Karl Popper behind it. And though Popper embraced the mess and grind because it was true, Deutsch also saw something beyond this. There was suddenly unique reason to be optimistic, not simply because progress could be made, but that we — if we play our cards right — will be able to understand and control the universe without limit; that progress could be literally infinite.

It is a broad and expansive line that takes us back to the birth of our species in the Great Rift Valley. Evolving as we did in that eastern corner of Africa, things appeared perfect by most metrics that we use today — the skies were clear, the rivers clean, and the surrounding environment as untouched by our footprint as by that of any other animal. Of course, it was also a situation for which we were genetically well suited. And yet we never had it so bad — stalked by predators, constantly on the edge of starvation, and with no protection from extreme weather, every moment was one of suffering and fear. We know now from the fossil record — just as has been the case with all other species that have ever existed — that this same environment in which we evolved, almost killed us.

It all comes down to the limitations of genetic knowledge. Relying upon undirected mutations, the constant improvements needed to keep ahead of natural changes in the environment, are just not something that evolution is capable of doing; at least not at the speed required. But even if it were able to do so, then those benefits would also apply to other animals (including our predators), and we would still have to suffer the same horrors and constant risk of extinction by virtue of the ensuing evolutionary arms race (micro-organisms and bacteria such as cholera bacillus evolved in this way specifically to kill human beings).

The only way that we ever managed to keep our heads above water, was with a new type of knowledge altogether — ‘explanatory knowledge’. No longer relying on the information in our genes, we could suddenly create knowledge ourselves. The process behind this remained a mystery until Karl Popper came along, but nonetheless it pulled us slightly out of the mud, and gave us the ability to dramatically change the world around us… if we chose to. The trouble was, people rarely ever did.

The immediate descendants of those people in the Great Rift Valley, despite migrating to new territory, and spreading out across the world, continued to live lives of incredible misery and desperation — the threat of death and extinction always biting at their heels. They had brains identical to our own, and so they also had the capacity to improve things exponentially. Yet — again from the archaeological and anthropological records — we know that from the standing point of any individual, nothing ever improved; the world that people were born into was also the world they died in (the artefacts — technology — we find from these periods can only be measured to an accuracy of about 10,000 years). The natural state of things was complete-and-utter stasis. This is hard to imagine based on how fast technology is improving today, and even harder to imagine when we realise that these people desired change just as much as we currently do.

Whether it was better hunting methods, better shelter, better clothing or better ways to protect themselves, our ancestors were constantly aware of how they wanted to improve their lives — they just didn’t know how to. And following this pattern, the vast majority of human history became one of unimaginable suffering, terror and extinction — right up until the Enlightenment

What changed at this moment, and what hadn’t existed until then (or at least hadn’t survived its early moments), was the establishment of what Deutsch calls a “tradition of criticism”. It came about largely through accident, and largely without people understanding its significance, but they had stumbled onto — in part — Karl Popper’s breakthrough long before he was born. Before this, all ‘traditions’ did just the opposite — they sought to avoid criticism, to avoid change, and to maintain stasis. The importance of this moment isn’t properly appreciated, because neither are the horrors of the static societies that came before it.

Unwilling to allow criticism, and therefore unable to make progress, we just don’t have any real record for most of these unchanging civilizations. They just didn’t survive long enough to etch themselves too deeply into history. Unable to innovate and correct errors, the first major, unexpected problem that came their way invariably wiped them out.

It was only by rejecting so-called authorities, and being free to question and criticise the world around us, that we began making rapid progress. And yet this still felt to many as cold comfort. We were improving our lives in remarkable ways, and yet for every problem we solved, new unforeseen problems were created (the industrial revolution was a solution to poverty, only for the by-product of those improved living standards — carbon — to become an existential threat of its own).

It still felt like we were only just a step or two ahead of death. That sooner-or-later we would begin to push-up against the ultimate limits of our knowledge, and so the next problem we faced could be a step too far — David Deutsch saw something different. Just as Popper had accepted the messy reality of things before him, Deutsch too started from a point of acceptance — “we shall never reach anything like an unproblematic state”. And so it is true that we might be doomed, but not regardless of what we choose to do. We can survive!

Every time we make progress we are solving problems, and every time we solve a problem, of any kind, we are creating new problems — but they are also better problems. The fact that problems keep arising, is never something that we will be able to fix. To be able to do so, would entail having access to future knowledge, to understand the unforeseeable. Yet despite not being able to comprehend future knowledge, we do have the capacity to deal with it — without limit. It all comes from that unique ability of ours to create explanatory knowledge, because there exists an intimate relationship between explaining the world and controlling it.

This is something that we do all the time, in what now often seems mundane ways. The world around us today, just as it was for our ancestors in the Great Rift Valley, is still a death trap. The only reason it doesn’t feel as such anymore, is by virtue of the explanatory knowledge we have already created. We no longer think about the problems of staying warm in winter, ensuring a constant food supply, or of avoiding waste-borne diseases, only because we have already invented clothing, agriculture and sewerage systems. The only people that do still think about these things, are those people trying to improve them (error-correction). Without the layers of technology that we have already built around us, most of us would die almost immediately — and yet for the most part we are thriving.

The only thing that makes any environment hospitable, is what the inhabitants of it actually know. And what we know, we can control. We might still fail to solve problems in time — in which case we will go the way of all other life — but through a commitment to learn from, and correct our mistakes — to always move on and embrace better-and-better problems — we have a chance… our only chance. And there is reason to be optimistic here. It is a messy, reality-based optimism just like Popper’s theory of knowledge — but also like Popper it is precise and doesn’t hinge upon utopianism.

It starts by doing away with hopes of prevention or delay. Approaches like these can be useful in dealing with any individual problem, but they can never constitute a future strategy in themselves. Trying to protect against — or trying to limit once they happen — future problems that we don’t yet know about, is a strategy that will quickly find its ceiling. It has the same logic of being told by a doctor that instead of treating your broken leg, he will instead show you how to avoid breaking it again in the future. For all its high-minded intent, it does nothing for your predicament right now — and in terms of existential threats, it means we only have to be wrong once for the whole project of humanity to end. To focus on problem avoidance rather than problem solving, will achieve very little of either.

Not only are these threats out there, and not only do we not know what they are, let alone how to deal with them, but there are also enemies of civilization — people who would seek to end the whole project by their own hand. Yet what all these problems have in common is their solubility, and what all these people have in common is that they are wrong. Thinking otherwise is not just to adopt the mindset of a static society, but also to adopt a mindset that — according to Deutsch — is deeply unscientific. Karl Popper has given us the tools to always stay ahead of these problems and these people, but it requires nothing less than a total commitment to achieving rapid, open-ended progress — the type of progress that static society ideology is just not capable of.

But this is not just a parochial arms race addressing cosmologically insignificant events, it is also our ‘Beginning of Infinity’. Stepping firmly ahead of Popper now, Deutsch saw what for some people might sound like a truism but — yet just like with Popper before him — has been almost completely misunderstood. That is, ‘any physical transformation not explicitly forbidden by the laws of nature, is achievable given the right knowledge’. It is hard for the full gravity of that statement to set in. It means that we can reach out across the universe, manipulate planets and stars as easily as we now do TV channels, and regulate the conditions of galaxies as easily as we now regulate the temperature of bedrooms. It means that the alchemists were onto something, they only failed to create gold because they didn’t have enough knowledge.

If there is a limit to what we can achieve, then that limit is also discoverable, comprehensible, and a law of nature. In the absence of such a law, everything — absolutely everything — is possible. And so we are capable of changing everything (the universe) at will, because there can be no such thing as a solution beyond our reach. Sure our problems often feel parochial — and they often are — but this is just because we are only at the beginning of David Deutsch’s infinity (and always will be).

When people talk about our niche in the universe being precarious, that we are insignificant, and so we need to be cautious and humble in what we do and what we desire, they are doing the one thing that will spell the end of humanity — turning away from rapid, open-ended progress, and toward stasis and stagnation. But perhaps worse, they are wrong! As beings capable of creating new knowledge (explanatory knowledge), and therefore of affecting the universe without limit, it follows from physics that we are of the deepest cosmic significance.

It is hard to imagine a universe without limitation in this way — and so the tendency is to imagine instead that even though explanatory knowledge has this unique reach to it, and although we have the capacity to create explanatory knowledge, we are still limited by our biology. Maybe other beings will be able to control the universe in this unbounded way, maybe even better evolved versions of ourselves in millions of years’ time, but not us! We are too broken, too incomplete, too much a product of our messy evolution. This misses the point of explanatory knowledge, and with it the lesson of universality.

Explanatory knowledge is a launch point, an escape valve after which there cannot be any other limitations, because with explanatory knowledge those limitations (problems) can simply be solved. And if we decide that the problem is our biological selves, then we could also simply solve this through improvements in our culture or nano-surgery in our brains. Without a foundation, our minds are completely fungible, and expandable without limit — we are entirely re-writable software. The principle of the ‘Universality of Computation’ means that there can be only one way of doing computation, and so the structure of our minds already contains the structure of everything. It feels god-like, but it is true, we are universal beings!

An open-ended stream of explanations is always available to us. The limitation is never resources (because all resources only become so by virtue of what people actually know) but only knowledge. It is never going to be pretty, but we can begin to step ourselves out of Karl Popper’s swamp, and to do so at ever greater speed. Progress of this kind in any one area, is also intimately linked with knowledge and progress in other areas; if technology continues to lead the way in this regard, as it does today, then progress in politics and morality will follow closely behind. The only dangerous thing we can do, is to think that some solutions are beyond our reach. “What lies ahead of us is in any case infinity. All we can choose is whether it is an infinity of ignorance or of knowledge, wrong or right, death or life.”