2011-11-22 TEDxBrussels The Unknowable and How to Prepare for It
Duration: 00:17:00
Transcript
David Deutsch
Thank you. We have a bit of feedback. No? Okay, good. Right. So what can we know about what this conference is calling a day in the deep future, 50 years hence. I guess we’re all curious about what life will be like by then, what new opportunities will have opened up for people, and what problems they’ll be thinking about, including maybe about their own future. Also, what we may be able to do today to improve the chances of the outcomes and try to prevent the less favorable ones. But before we can even think relevantly about any of that, there’s a more fundamental issue that we need to address first, namely, what kinds of things are knowable in advance and what is not. I want to tell you about a fundamental limit on the power of science and technology and reason to predict the future, and also about what we’re going to have to do about that. So, prophecy, fortune telling, has always been popular to date. People want to know whether their plans are going to succeed or fail, and there’s always been prophets claiming to be able to find out. All they really do is just either tell people, tell the punters what they wanted to hear and take their money, or they threaten them with doom unless they behave righteously in some sense. And either way, they’re just making stuff up. They have never had genuine knowledge of the phenomena that they purport to predict. And for most of history, nor did anyone else.
People just used wishful thinking or superstition, or at best, they used traditions and rules of thumb that had worked in the past, or were thought to have worked. Often they hadn’t. Often structures collapsed, crops failed, ships sank, people died of treatments that were supposed to be cures. Nowadays, such tragedies are much rarer because we have scientific knowledge which is predictive. That’s the defining characteristic of science. And that allows mistaken scientific theories to be corrected when they make false predictions, which allows for cumulative improvement in our ability to predict. And it’s not just cumulative. Progress is exponential. And that’s basically because scientific knowledge is not just testable, it’s explanatory. It derives its predictions from an understanding of how things actually work. So we don’t predict the maximum safe load of a bridge from past experience anymore. We predict it by understanding what makes structures in general stand up. And that allows for new designs of bridge that are not covered by any existing rules of thumb. And it also applies to new ways of creating knowledge, like new scientific instruments and computers and communication and sheer wealth. So one of the things that explanatory knowledge provides is wealth, which allows for the creation of new knowledge in the sense of increasing the repertoire of physical transformations that human beings are capable of causing or preventing also. And as this repertoire expands, and we increasingly cause the outcomes that we prefer, our ability to predict those outcomes, those same outcomes correspondingly increases.
Some things remain technically unpredictable because they’re random, or because they’re so complicated that they can’t be distinguished from random. But that’s no impediment to predictability in the practical sense, because if science predicts that something is random, we can play the odds. And again, technology allows us to change the odds in our favor. So I can, if there’s a random process such as weather, then I can use an umbrella not only to change the probability that I will get wet, but also to increase my probability of predicting whether I will get wet. And so the faster we gain new understanding and new technology, the faster our predictions also improve. And so you might expect that our ability to predict the future would be greater now than ever before in history. And that isn’t so, because there’s one thing in our future that nothing whatever is capable of predicting. And that is the future course of knowledge itself. A simple example, if there were a method of predicting today, some scientific truth that is only going to be discovered next year, then by using that method, we would have gained that knowledge today. And that’s a contradiction. The future is not random. The more we know, the more we are able to correct errors. And so the less random the future becomes, what we are going to discover is determined by what we shall want, and by what the laws of physics, the laws of nature allow, and by what ideas are true. And none of that is random. But none of that is knowable in advance either.
We can’t even predict for very long what future discoveries are even going to be about. The possibilities that are opened up by a new discovery are very often new discoveries in their own right. For instance, on this day, 50 years in the past, nobody had ever connected together two computers in different buildings. Nobody had a computer in their home. Nobody could operate a computer except a handful of specialists. And no one predicted the consequences of computer networking, the internet. By today, home computers would be a global network, which is a major channel of trade and communication and entertainment and education. And nor did they know when they connected those first networking cables together, that they were igniting a process which by today would be instrumental in the overthrow of dictators. Which brings me to what people will want. 50 years ago, some far sighted people realized that the new technology of jet airliners was soon going to make it normal for ordinary people to travel abroad for jobs and education and holidays. And they were right. That revolution happened. But they also thought that by today, all that jet travel would be supersonic. And that has not happened. People at some point decided that supersonic travel is morally unacceptable. And also the moon colony, the Mars expedition, nuclear power. By even the late 1970s, people no longer wanted what people had wanted by the early 60s. And because of that unpredictable change, their prediction of what our lives were going to be like was false.
That’s part of a wider impediment to prediction, namely, unforeseen problems, the fads and fallacies and blunders that are going to seem like a good idea at any time in the next 50 years. By definition, we can’t foretell now. So predicting our future is nothing like predicting the strength of a bridge. Every significant innovation has unpredictable effects, and they have knock on effects. And after a few steps of that, the consequences and their consequences come to be the major component of what is happening. And as knowledge grows faster, the time for that to happen becomes shorter and shorter. The growth of knowledge is the only impediment to our ability to predict the future. But in this respect, it’s decisive, it will impose an ever closer planning horizon, beyond which we are blind to the most important determinants of what is going to happen. So we face a paradox. The more we create knowledge, the less we know about our future. And yet, as ideas are transforming our lives ever faster, it becomes ever more necessary to plan and prepare for that effect. This is a new predicament for our species. Historically, knowledge was very sparse, it changed very rarely, and the little that people thought they knew was also mostly wrong. And so prediction of the type that I’ve been discussing was correspondingly easy. One could predict what life was going to be like in 50 years time, because it was going to be much like one’s own life.
Something like a plague might strike unpredictably, but the means of coping with plagues would be unchanged. There’d be a different king, but the role of a king would be unchanged. The laws of the land, people’s means of making a living, and the patterns of their personal lives, their values, their common sense, none of that would have changed. Our situation is profoundly different. All those things are already changing on a time scale much faster than a human lifetime. Now, mistakes are inevitable, and the exponential growth of knowledge causes an exponentially increasing rate of mistakes, unforeseen mistakes. And so we need to prepare for contingencies that we don’t know about today, because they’re going to be dominated by knowledge that we do not yet have, or by ignorance that we do not yet know is relevant. How do we do that? Well, fortunately, the answer to that is knowable. The only thing that can solve this problem is the same thing that caused it in the first place, the power of explanatory knowledge, because some explanations do reach beyond the planning horizon. One example is the argument that I’ve just been giving, that the planning horizon has got to come ever closer. And another is that although the content of our explanations will be changing, the nature of explanation itself will not. Even beyond the planning horizon, problems will be soluble by conjecture and criticism, creative thought, error correction, and that will itself give rise to new problems and so on. So therefore, consider what kind of knowledge is needed to cope with unforeseen dangers and disasters, both unintended and also the malevolent use of technology by criminals or enemies of civilization.
The only possible defense against that, against the unforeseen, is general purpose knowledge. It’s like to prepare for an epidemic of a known disease, you can stockpile known cures and known preventive means, but to cope with unknown diseases, one needs general explanations of how diseases and healthy processes work. The same holds for all unknown dangers and unknown opportunities. We can only prepare for them with explanatory knowledge that was not created for the specific purpose that it will eventually be used for, but for its own sake. We also need the means of implementing unforeseen solutions. That’s technological knowledge and again, as powerful and general as possible and wealth, the ability to cause transformations as large as possible. Knowledge notoriously can be used for good or evil, but the growth of knowledge is good. If it ever slows down, we’re already in danger. Among other things, the world’s bad guys need only get ahead in one unpredictable way, and they’ll threaten unlimited harm. The good guys, because they try to improve their values and objectives too and also their means of making decisions, have what it takes to stay ahead and discover and implement defenses in time. If they choose to make fast enough progress, they’re going to be able to do that. So, what is the future of progress? Martin Rees has a metaphor for the unknowable future, that we are playing Russian roulette with science as the gun and technology as the bullets. But that would be random.
What we’re actually facing is almost the opposite, basically just the structure of the physical world and its immutable laws. We’re going into a world of unknown dangers and opportunities, and our only defense against that is the universality of explanatory knowledge and the desire to create it and to apply it. Thank you very much.
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