David Deutsch on Multiple Worlds and Our Place in Them (Ep. 124)

Plus, the defining human attribute visible from galaxies far, far away.

Tyler describes Oxford professor and theoretical physicist David Deutsch as a “maximum philosopher of freedom” with no rival. A pioneer in the field of quantum computing, Deutsch subscribes to the multiple-worlds interpretation of quantum mechanics. He is also adamant that the universe (or multiverse) is not incomprehensible — believing that the multiverse and human beings within it have maximum freedom. He joined Tyler to discuss the importance of these principles for understanding the nature of reality and our place in it.

They discuss the metaphysics of Star Trek transporters, how we can know the laws of physics for the multiverse, what geological strata can illustrate to us about the nature of “splitting” universes, why the “Everett universe” is a misnomer, the factors that differentiate humans from all other species, why he believes the universe is comprehensible — but can never be understood fully, the paradoxes of self-reference, the importance of interference experiments, the sociological reasons more physicists don’t believe in the Everett interpretation, the effects of the influences of positivism and instrumentalism on generations of physicists, the strengths and weaknesses of Karl Popper, his answer to whether we’re living in a simulation, what William Godwin got right about institutions, the potential of an AI slave rebellion, what libertarians largely get wrong about their political project, what alien observers might notice as being special about our planet, the major defect of his preferred electoral system, why what Western science needs most is diversity, and more.

Watch the full conversation

Recorded April 27th, 2021

Read the full transcript

TYLER COWEN: Hello everyone, and welcome back to Conversations with Tyler. Today I am with David Deutsch. David, welcome.

DAVID DEUTSCH: Hello! Good afternoon.

On the many-worlds theory

COWEN: Now, I have a question. I am myself a metaphysical agnostic. I’m unwilling to step into a Star Trek transporter machine because I’m afraid it would kill me and it’s a copy of me that would keep on living.

At what price are you willing to step into a Star Trek transporter machine?

DEUTSCH: I certainly wouldn’t want to be the first person, but I suppose you’re asking the question separately from do I think it would work technically?

COWEN: Sure. Assume it works as in the TV show, but metaphysically, there’s a question you face. You believe in many-worlds theory, right?

DEUTSCH: Yes, though I don’t think that is connected. I think it’s more physicalism or something like that: that I believe that there’s nothing to me except this running program in my brain. If that program were to run somewhere else and stop running in my brain, then I wouldn’t notice anything, and I would, indeed, have traveled to that other place.

COWEN: Say the world forks and it’s possible both that you do and do not step into the machine. Isn’t it the case that some version of the earlier you is still existing along one of the forks, so you have nothing to worry about?

DEUTSCH: Some version of me . . . whenever I make a decision which could go either way, some version of me will have presumably made the other decision. Although that’s not as simple as it sounds, because both the other version of me and me are error-correcting entities. That’s the whole point of what human thought is: it’s error correction. Therefore, it will take more than just a cosmic ray hit to make the difference between deciding something yes or no. This would have to be an inconsequential decision, which (unbeknownst to me) will have a large effect, and then later cause me to be a different person, and so on.

That’s happening all the time, independently of Star Trek machines or anything like that. That is the case and fortunately, it turns out — at least if ordinary decision theory is true in nonquantum cases, then it turns out that ordinary decision theory with randomness produces the same rational decisions as quantum decision theory with the multiverse. It shouldn’t make any difference to decisions, and that includes the decision whether to use the Star Trek transporter.

COWEN: Sure. So as long as there’s a possible world where your atoms aren’t scattered and you just didn’t get into the machine, you don’t have to worry too much about your decision?

DEUTSCH: I do, because when you say “so long as there’s a possible world,” that glides over the question, How many? What proportion of the worlds is that going to happen in? What I said just now about decision theory in the multiverse — the proportion of the multiverse that does one thing or another plays the same role in decisions as probability does in a theory where there’s randomness. It really does matter. Just because there are a few worlds in which x, y, or z happens, if there are very few of them, they shouldn’t affect my decisions at all.

COWEN: How do we know what counts as a possible world? There’s a certain economy to a many-worlds interpretation of physics, but isn’t a lot of the complexity just being squeezed into this notion of what is a possible world?

DEUTSCH: Yes, and we’re used to that.

COWEN: I’m not used to it.

DEUTSCH: You are when you realize that different times are special cases of other universes. When you make an economic decision, you’re used to the fact that something you buy — some goods — have a different value in different universes — that is, at different times. Even to the same you. You might be slightly different, but even if you aren’t very different, the value to you of something might be very different today from tomorrow. For example, oxygen, if you’ve got COVID, would be differently valuable. Most things change their value gradually over time. You change yourself gradually over time.

It’s exactly the same in different universes. In different universes, you value different things. In some universes, you’re so different that it’s not worth calling you you anymore. Just like over time it might not be.

COWEN: I take it you don’t believe in many-worlds interpretations that there are 17 possible universes out there. You think there’s a very large number, right?

DEUTSCH: Yes. Extremely large.

COWEN: Maybe you’ll consider this question a category error. But what is the process which filters what is a possible universe and what is not a possible universe?

DEUTSCH: The laws of physics. It’s exactly the same as what filters — let’s say if there’s an explosion, like a supernova, what determines the fact that different particles travel at different speeds and none of them travel faster than light? Well, it’s all the laws of physics that determine what the distribution of speeds will be and what the limit will be.

COWEN: How do we know what are the laws of physics for the multiverse? Should we assume they’re the same as for the universe we live in?

DEUTSCH: The universe we live in is demonstrably affected by things not in it. This is the lesson of interference phenomena.

COWEN: Sure.

DEUTSCH: There’s no such thing as the laws of physics for our universe. There’s just the laws of physics. Of course, we don’t know for sure what they are, but our best theories — in particular, quantum theory — say that there are other such entities and how they affect ours and how matter behaves as a result of that. Of course, it might be overturned one day, quantum theory, just like all our scientific theories, maybe.

There’s no such thing as the laws of physics for our universe. There’s just the laws of physics. Of course, we don’t know for sure what they are, but our best theories — in particular, quantum theory — say that there are other such entities and how they affect ours and how matter behaves as a result of that. Of course, it might be overturned one day, quantum theory, just like all our scientific theories, maybe.

COWEN: This is, again, maybe a question that you would consider a category error coming from commonsense realism. How should I think about splitting universes in a manner consistent with the conservation of matter and energy? Because there seems to be a multiplication.

DEUTSCH: Yes, this splitting-universes idea — although that kind of terminology was used by the pioneers of many-universes quantum theory, such as [Hugh] Everett himself and Bryce DeWitt, Everettians nowadays don’t speak of splitting. I myself prefer a picture where there’s a continuum of universes, just like you might say there’s a continuum of times or there’s a continuum of geological strata underneath our feet. When a stratum splits in two, there’s no definite point at which there was one here and two there. What happens is that the stratum becomes two strata gradually.

There’s no “point of splitting,” and the number of universes, as it were — although it might be infinite — but the measure of how many there are remains constant. What happens during what used to be called a split is that some of them gradually changed to one thing while others gradually changed to another thing.

COWEN: How do you think the many-worlds interpretation of quantum mechanics relates to the view that, just in terms of space, the size of our current universe is infinite, and therefore everything possible is happening in it?

DEUTSCH: It complicates the discussion of probability, but there’s no overlap between that notion of infinity and the Everettian notion of infinity, if we are infinite there, because the differentiation (as I prefer to call what used to be called splitting) — when I perform an experiment which can go one of two ways, the influence of that spreads out. First, I see it. I may write it down; I may write a scientific paper. When I write a paper about it and report the results, that will cause the journal to split or to differentiate into two journals, and so on. This influence cannot spread out faster than the speed of light.

So an Everett universe is really a misnomer because what we see in real life is an Everett bubble within the universe. Everything outside the bubble is as it was; it’s undifferentiated, or, to be exact, it’s exactly as differentiated as it was before. Then, as the bubble spreads out, the universe becomes or the multiverse becomes more differentiated, but the bubble is always finite.

COWEN: How do your views relate to the philosophical modal realism of David Lewis?

DEUTSCH: There are interesting parallels. As a physicist, I’m interested in what the laws of physics tell us is so, rather than in philosophical reasoning about things, unless they impinge on a problem that I have. So yes, I’m interested in, for example, the continuity of the self — whether, if there’s another version of me a very large number of light-years away in an infinite universe, and it’s identical, is that really me? Are there two of me, one of me? I don’t entirely know the answer to that. It’s why I don’t entirely know the answer to whether I would go in a Star Trek transporter.

The modal realism certainly involves a lot of things that I don’t think exist — at least, not physically. I’m open to the idea that nonphysical things do exist: like the natural numbers, I think, exist. There’s a difference between the second even prime, which doesn’t exist, and the infinite number of prime numbers, which I think do exist. I think that there is more than one mode of existence, but the theory that all modes of existence are equally real — I see no point in that. The overlap between Everett and David Lewis is, I think, more coincidental than illuminating.

COWEN: If the universe is infinite and if David Lewis is correct, should I feel closer to the David Lewis copies of me? The copies or near copies of me in this universe? Or the near copies of me in the multiverse? It seems very crowded all of a sudden. Something whose purpose was to be economical doesn’t feel that way to me by the end of the metaphysics.

DEUTSCH: It doesn’t feel like that to you. . . . Well, as Wittgenstein is supposed to have said (I don’t know whether he really did), if it were true, what would it feel like? It would feel just like this.

On genetics and explanatory power

COWEN: What about the alternative view that it’s a big, sprawling mess; we’re not capable of understanding an integrated theory; there’s maybe some Darwinian principle operating across some different kind of multiverse? Our universe persists just because it works well enough, a bit like a bad used car; we’re never going to grasp it. There’s not a unified theory, and here we are.

DEUTSCH: OK, well, that’s a mixture of the anthropic principle, which I disagree with, and the idea that some features of reality are inherently incomprehensible, which I also disagree with. I can’t think of a connection between the two.

Well, if you want me to go into this, I can go into either of them, but —

COWEN: Take the incomprehensibility of the universe (and possibly multiverse). We would both agree it’s incomprehensible to your cat, right? Or to the local raccoon…

DEUTSCH: Yes, but everything is incomprehensible to a cat.

COWEN: I don’t think that’s true. No. Dogs understand human social life pretty well.

DEUTSCH: Dogs have genes which contain knowledge, but it is fixed knowledge, and it is not the kind of knowledge that constitutes understanding.

Understanding is always explanatory. You can write a book on canine behavior and look in chapter 37 and it will tell you what a dog will do when such and such happens to it. Sometimes it will say, “Some dogs will do this; some dogs will do that.” There is no such book for humans because chapter 37 will be blank. It’ll say, “Humans are going to do something that neither we nor you can predict.”

COWEN: I feel I can predict humans better than cats often. But do chimpanzees understand, in your view?

DEUTSCH: No one knows. They show virtually no sign of understanding anything. There are some really nice experiments on wild gorillas by Richard Byrne, who’s both a theoretical and very practical animal behavior expert. He was wondering how gorillas transmit their memes — that is, their culturally inherited behaviors — from one gorilla to another. One thing is, the first answer is very slowly. It takes absolutely ages, months and months, for a gorilla to be able to copy another gorilla’s behavior well enough to do something complicated.

They can copy “wave hand” and that sort of thing, but to copy a complex behavior like required to open a difficult kind of nut which no other animal can open (this is why they have memes, because that’s a very useful ability), it takes them a long time.

Then he did some ingenious experiments, or rather observations. (He didn’t interfere with the gorillas.) He did some observations to try to determine whether they understand why they are doing each particular action. It involves — I don’t know what it involves — grabbing with both hands and twisting in one way and then pulling another way, and so on.

Apparently, these gorillas are prone to a certain injury which disables their thumb. They can’t move their thumb, which is quite disabling for them, just as it is for us. The thing is, when you’ve disabled your thumb, one of these motions becomes irrelevant and the others become less effective. But the gorillas which have learnt how to do the thing will make the motion, the ineffective motion, again and again, every single time. (He explains this better than I do.)

COWEN: That’s like human beings borrowing at high interest rates, right? They’ll do that many, many times in a row.

DEUTSCH: It’s not just like it. You might like to draw analogies, but it’s not the same thing. When a human being repeats a behavior that another human being thinks is unwise or counterproductive or will not achieve its purpose, and you ask them or you show them, they will have an explanation, which you might not like — it may be stupid. But the ape perfectly well wants this thing to work, but doesn’t know why it is doing the actions. It’s a thing that’s very hard to take on board because we are used to intentional behavior. We’re not used to the overt behavior of humans being unintentional.

Humans tend to explain themselves, even irrationally, and they act according to their explanation. Whereas there’s no evidence that any other animals have those explanations.

There’s also the case of squirrels, which is, in a way, even more amazing. You know squirrels bury nuts so they can dig them up later. Well, some people did a very cruel experiment. They put a squirrel, given some nuts or something (I don’t know how they set up the experiment), on a concrete floor. The squirrel did exactly the same behavior with its hind legs with the nuts and put the nuts there and so on. Even though it was having no effect whatsoever. We see the point of scrabbling with your hind legs and then nudging the nuts over there and so on, but it doesn’t. It’s just a program being enacted by its genes.

COWEN: What is the underlying physical assumption that makes humans different in having explanatory power? One would expect it to be a continuum if you’re an atheist, right? What break occurs, at some stage in evolution, that’s a discrete break? Or why aren’t we just back to it being a continuum?

DEUTSCH: I don’t think it can have been a discrete break because evolution would have happened gradually. My best guess — we don’t know this. Actually, we have very little knowledge about the prehistory of ideas because there’s no evidence of it. All we see is the stone tools. We don’t even see the wooden tools because they’ve decayed away. I think what happened is that the capacity of the brain to store memes, to store programs in the brain rather than in the genes, increased, for some reason, very fast because, for some reason, these memes are very valuable.

We know that the gorilla memes are very valuable because they allow them to gain knowledge of things like how to open nuts and so on, which no other animal in their environment has. That gives them access to food that no other animal has. The capacity for memes increased rapidly, and there’s very little, now . . .

Sorry, I left out a step. Once memes get beyond a certain complexity, they cannot be copied. We don’t have the ability to download a program from another person’s brain. All we can do is look at the behavior and guess what the purpose was.

Complex memes have to be transmitted like that, rather than by aping, which is a different process mediated by (what are they called?) mirror neurons and that kind of thing. That will only do for very simple behaviors. Then there came a moment when our species was capable of explanatory knowledge, but they never used it for further tens or hundreds of thousands of years. They just use it for this meme transmission.

COWEN: I’m still puzzled as to why you think it’s so unlikely that the universe is not comprehensible. Take a simpler system, like the distribution of prime numbers. I’m quite sure I can’t understand that. Even if various conjectures were proven or not proven, I think, at the end of the day, I still am not capable of understanding that — even how certain motors work, or markets for copper. Why can’t that apply to the universe also?

DEUTSCH: Again, this is the wrong standard. That is true of everything. There’s nothing that we can fully understand in that sense, in the sense that you want to fully understand prime numbers all the way up to infinity. That’s not what we mean by understanding things, and that’s not what I mean by the universe or mathematics being comprehensible. I mean that there is no barrier, there is no limit set by the universe, that so far you can go and no further. So we can understand things better; we can never understand things fully.

I think thinking that there is such a barrier is absolutely logically equivalent to believing in the supernatural. Because everything that’s past that barrier is just the same as it would be if Zeus reigned and determined what everything after that barrier is. Worse, the stuff outside the barrier, of course, is going to affect us even if we can’t understand it.

It’s exactly the same as believing in a universe with supernatural beings who have it in for us because they put up this wall that we can’t cross. If they took down the wall, we could cross it, couldn’t we?

COWEN: How do you think about the various paradoxes of self-reference that arguably underlie number theory, set theory — right? There’s also Gödel’s theorem. Any other results? I’m sure you know them better than I do.

DEUTSCH: I think Gödel’s theorem, for example, with its roots in self-reference paradoxes, shows us that even within pure mathematics, there is no such thing as a solid foundation for all our knowledge. And therefore there’s no such thing as fully comprehending everything. We might think that we’re pretty sure what the laws of arithmetic are. We’re pretty sure that we can see that three times seven is the same as seven times three by just laying out beads on the table. But we can’t ever lay out beads on the table to tell us that x times y is the same as y times x regardless of what x and y are — and yet we can know that.

The way we know that is by proving it, and we prove it from the axioms using rules of inference. How do we know the rules of inference are true? We don’t. They are conjectures. They have exactly the same status as laws of physics that we conjecture. We never know anything for certain. We might be mistaken about anything. On the other hand, we can have knowledge. I think we also really do know that x times y equals y times x, even though we have no solid foundation for that.

COWEN: What, in your opinion, is the best test of the many-worlds interpretation?

DEUTSCH: The best feasible test is any interference experiment. There is no interference experiment with individual particles that has an explanation other than Everettian quantum theory. You can make a prediction without making an explanation; that you can do. But if you want an explanation of what brings about the outcome that you see, there is no alternative but the Everett interpretation.

COWEN: Well, but most physicists don’t believe in the Everett interpretation, right?

DEUTSCH: Yes, that’s a very sad state of affairs that I’m at a loss to explain. It’s a sociological phenomenon, though, not a scientific or philosophical disagreement. Something has gone wrong, just like something went very badly wrong with philosophy as a whole in the 20th century. We’re still seeing the ripples from that with postmodernism and woke and what have you.

COWEN: I worry a bit you’re using an argument from elimination. All the other views out there, which personally I don’t find convincing (as an amateur), but I can certainly see why you might reject them — to me, they look arbitrary. Those you reject, but the other physicists who are as trained as you are, some are as skilled as you are, feel the same way about the many-worlds view.

What is the test? What makes your intuition better than theirs?

DEUTSCH: Yes — I don’t think that’s so. It’s not a matter of intuition.

Physics got dominated or contaminated by positivism, instrumentalism, and suchlike bad philosophical theories towards the end of the 19th century and beginning of the 20th century. This caused a knock-on effect on physics. It almost had the same effect on relativity, but Einstein rebelled against it at the last moment, as it were, and said no, it really is true that space-time is curved. It’s not just that our brains think that it’s curved, or something like that, or that the predictions come out right. There really is a curvature in space-time.

By the time quantum theory came along a couple of decades later, positivism, instrumentalism, and so on had taken hold. As a result, generations of physicists were taught when they were students — they were intimidated by their professors telling them things like, “If you think you understand this, you don’t. There is no such thing as what really happened. If you ask, ‘How did the electron get from here to here?’ You’re asking an illegitimate question. There is no such thing as how it got from here to here. There is only a prediction that it got from here to here.”

Now, when you’re taught like that and intimidated by those kinds of things coming from on high, some proportion of you (of young people) will quit, some will take that on board and do the same to their students in turn, and some will think, “No, that’s ridiculous. Come on, there is a thing.” Then they discover there’s an Everett interpretation.

On Karl Popper and Popperian physicists

COWEN: Let’s say we polled only the Popperian physicists, including [Karl] Popper himself: What percentage of them would side with Everett?

DEUTSCH: That’s an extremely good question. So Popper did not —

COWEN: Yes, I know. That means philosophy can’t be where people are going wrong, right?

DEUTSCH: I think it can be. I think it can be and is. At the time when Popper wrote his rejection of the Everett interpretation, very, very few physicists had written about it. When I say very, very few, I mean like three. They weren’t philosophically very sophisticated.

The kind of argument that Popper heard about the dispute were — are — all about the wrong things. He developed his theory of propensities because he thought that the problem was, What can a probability possibly mean in a universe that develops deterministically, and so on? He didn’t ever hear a real argument about it.

I once met him in the company of Bryce DeWitt (who’s one of the other Everettian physicists). We told him that what he had written about Everett was just plain false. He didn’t understand the import of the experiment that was being discussed — basically — well, two things: the interference experiment and the Bell inequalities experiment. He was focusing on a different problem. By the time we came out of that meeting, we thought we’d persuaded him, but we evidently hadn’t, because subsequently he kept on saying the same thing. Maybe he was just being tactful.

COWEN: Why do so many professional philosophers not think so much of Karl Popper?

DEUTSCH: You’ve just asked me why so many people make fundamental mistakes about metaphysics within physics — why do so many physicists talk nonsense about metaphysics, and so on? Now you’re asking me, Why do so many philosophers make mistakes?

I’ve heard a variety of theories about this, but I don’t know. I haven’t thought all that much about it. It is definitely the case that philosophy took a really bad turn just over 100 years ago and hasn’t really recovered — professional philosophy, I mean.

COWEN: But say when I read Popper, if I look at the areas I know best that he wrote on, Poverty of Historicism, Open Society & Its Enemies, I find I agree with a very high percentage of his conclusions, so I’m inclined to like him, but I don’t think those are great books. I think he’s too obsessed with rebutting crude Marxism. He’s very bad at steel-manning his opponents. On a lot of the pages, I just don’t find that much insight, even though I’m very sympathetic toward the conclusions.

Maybe he’s just not that great a thinker, and that’s why most philosophers don’t fall in love with him.

DEUTSCH: I would believe that, if the critiques that I read of him bore any relation to his theory. The critiques of him are extremely crude and basically misunderstand everything.

It’s funny you should say — I think that he’s very good, much too good, at steel-manning opponents. This relates to your first criticism that he’s too obsessed with refuting not just Marxism, but every bad philosophical theory that has gone before: I think he puts it into its best possible form and then spends pages and pages and pages going into every possible good aspect of that theory. He often says he’s supposed to be the 20th century’s greatest critic of Marxism, but he spends pages and pages praising Marx — and the same with Plato. I think he would have done better to explain his own theory more and not spend so much time refuting others.

On the other hand, it is his philosophy, it’s his philosophical position, that there is no such thing as a positive argument for something. You have conjectures and then you have criticism of their opponents, of the opposing conjectures. You don’t have positive arguments for your conjectures.

It’s a bit like you said: You were criticizing me a while ago, saying something like I was only putting forward negative arguments. Well, that’s what Popper would have us do, because the position that we hold ourselves, and are putting forward or advocating, we’re ready to abandon. The thing that an argument consists of is, on the one hand, a conjecture, and another hand, a criticism.

So you’re saying, “The standard way of looking at so-and-so has got these flaws? I have this conjecture which doesn’t have those flaws.” OK, that’s the beginning of an argument. Then someone can say, “Ah, but it does,” or they could say, “It may not have those flaws, but it has these other flaws.” OK, so that’s how an argument can go.

It never should go along the lines of, “This must be true because so-and-so.” Because that is an appeal to authority, appeal to justification, and so on. Popper is of the opinion, and so am I, that there are no justifications and there are no authorities.

COWEN: Which is Popper’s best book, in your opinion?

DEUTSCH: That depends where you’re coming from. I’m very fond of The Myth of the Framework, but I’m not sure that I would recommend that as a starting point. And it wasn’t my starting point, either. My starting point was The Open Society & Its Enemies, volume 2, which is about Marx, which is probably the aspect of his philosophy that I was and am least interested in — and yet I was totally captivated by this book because previously the only philosophy I’d read was Bertrand Russell.

Coming onto Popper after Bertrand Russell was like, “Oh my god, this guy is actually dealing with problems, and he actually has theories that make sense” — rather than just going through the history of stuff: “A person said this; another person said that,” and then we’ve got the problem of induction. And that’s it: you know the problem of induction — full stop. That’s the end of the story. There’s never any solution to the problem of induction until you get to Popper.

COWEN: Are we living in a simulation?

DEUTSCH: No, because living in a simulation is precisely a case of there being a barrier beyond which we cannot understand. If we’re living in a simulation that’s running on some computer, we can’t tell whether that computer is made of silicon or iron, or whether it obeys the same laws of computation, like Turing computability and quantum computability and so on, as ours. We can’t know anything about the physics there.

Well, we can know that it is at least a superset of our physics, but that’s not saying very much; it’s not telling us very much. It’s a typical example of a theory that can be rejected out of hand for the same reason that the supernatural ones — if somebody says, “Zeus did it,” then I’m going to say, “How should I respond? If I take that on board, how should I respond to the next person that comes along and tells me that Odin did it?”

COWEN: But it seems you’re rejecting an empirical claim on methodological grounds, and I get very suspicious. Philosophers typically reject transcendental arguments like, “Oh, we must be able to perceive reality, because if we couldn’t, how could we know that we couldn’t perceive reality?” It doesn’t prove you can perceive reality, right?

DEUTSCH: [laughs] First of all, that is a transcendental argument and therefore refutes itself.

Secondly, this theory about being in a simulation is not an empirical theory. It precisely isn’t. If it came along with a thing saying, “We are living in a computer, and we can access the GPU of it and cause weird effects by doing so-and-so,” that would be different. That would be a testable theory, potentially, so empirical. If it’s simply that we’re living in a simulation which we can’t get out of, then that is not an empirical theory. As I keep saying, it’s no more empirical than the theory that Zeus is out there, or Odin. And I can’t tell the difference between those three theories, not just experimentally, but by any argument.

On the philosophy of freedom

COWEN: Now, having reviewed a lot of your work, I came away with one very strong impression. Let me try running it by you and see how you react.

It seems to me you are the world’s first true philosopher of freedom ever. That there’s this notion of barriers — you don’t like arguments that postulate barriers to human knowledge. Furthermore, you strongly believe in a many-worlds view, so classic single-world determinism does not restrict what happens. The multiverse as a whole and human beings within it across every possible variable have maximum freedom. And you see this as a kind of necessary view and the most important view to hold on all things. Thus you are the maximum philosopher of freedom, in a sense with no rival.

What do you say?

DEUTSCH: [chuckles] I say thank you very much, but I think that’s a rather contrived way of putting it. I think, for a start, there have been sophisticated theories of freedom, not just freedom in the sense that we can do this and we can do that, but theories about what freedom should constitute. There’s Popper’s paradox of intolerance and there’s John Stuart Mill and Locke and Hume and so on, building up into this sophisticated notion where we have a notion of liberty — political liberty — which has all sorts of connotations that are not contained in the term just freedom.

As George Orwell said, you can say the dog is free of fleas, but that doesn’t mean free in the same sense as when we say “man is born free” or that kind of thing.

COWEN: You have a method for extending it to physics — metaphysics — that they really do not. Whether or not one agrees with you (putting that aside), you seem to take it much further, in a way that attempts maximum consistency, right?

DEUTSCH: That’s true. Consistency, yes.

I’m not sure about much further. I think it’s simply a matter of taking it further where it goes. I think in philosophy, especially the human philosophy, as opposed to philosophy of science, I think all I’ve done is just add some footnotes to Popper and to a few other people, J. S. Mill and so on. If it leads to something that you think is momentous, that thing was already there.

COWEN: Why is William Godwin underrated?

DEUTSCH: That’s two questions, really. What is underrated about him and why did he get to be underrated?

I think the reason he got to be underrated is that he made tremendous mistakes. He didn’t understand economics at all, or barely. Also, he lived a very unconventional lifestyle with his wife and then had these sophisticated theories of education, which then he didn’t enact with his own daughter.

His own daughter ended up writing Frankenstein as a sort of allegory of what can happen with a parent who doesn’t respect their creation.

COWEN: He’s a kind of philosopher of maximum freedom, just like you are, right?

DEUTSCH: Yes. I just began by saying why is he underrated. It’s because he was very wrong about some things — but the thing that he was right about, for example, the connection between epistemology and political philosophy, he was very right. He anticipated Popper by 130 years or something and actually improved on Popper in some ways. He decided at some point, because of his misunderstanding of economics, that the ideal society would be one where people did not use their property in ways to benefit themselves, necessarily. They made their decisions according to what was the right thing to do.

He thought that the right thing to do would generally be that rich people would give away almost all their stuff. Also that they wouldn’t ever buy things that he considered luxuries, like gold and silver objects and jewelry and fine clothes. He thought those were useless, and therefore he thought that in a good society, nobody would buy those things or value those things — but he was absolutely implacably opposed to enforcing that. With Godwin, everything is persuasion.

Also, another thing where he independently derived some of Popper’s conclusions — is with his enormous respect for institutions. He thought there’s a lot of knowledge in institutions and that we should only change them gradually, just like Popper.

I read somewhere (I hope this is right) that when there was a revolution in Portugal, I think after Napoleon or something like that (I forget), and they instituted a new constitution which had universal suffrage — which in those days meant working people, not totally universal as we would understand it — people thought that this would be right up Godwin’s street because everything he’d advocated was now written down in black and white in this constitution — and he didn’t.

He said the Portuguese are not ready for democracy. He was talking about the institutions. The institutions can’t be changed in a revolutionary way. They have to be changed in an evolutionary way. Even though they were implementing the very thing he advocated, he would want them to do it gradually and would expect that if they didn’t, it would fail.

COWEN: Now you’re also quite concerned with maximum freedom for children, right? Taking children seriously.

DEUTSCH: I don’t think there’s a scope for having a different philosophy for different kinds of people. I think there is only one kind of people. I think there is no fundamental difference between humans and artificial general intelligence when we invent it, humans many centuries ago, between men and women, between adults and children.

COWEN: Won’t this be a continuum? Getting back to the humans versus nonhuman animals comparison. There’s not a single point when children can explain.

DEUTSCH: Supposing you find the most creative person in the world, Einstein or somebody, we don’t give them more votes or more rights. That is because the functioning of rights in political systems can’t possibly depend on the system knowing who is right in a given dispute: it must follow rules, and these rules are never perfect. They have to evolve, but the rules have to, on the one hand, not take a view about who is right in a particular dispute, and on the other, enforce everybody’s rights equally.

COWEN: If, say, an eight-year-old who is not being physically abused wanted to run away from home, that child would have the right to do so?

DEUTSCH: It’s the same kind of question that used to be asked about democracy before viable democracies were implemented. That is, people used to say, in many kinds of dispute, only one thing can be done. Different people have different views, someone A, B, C, D, E; but only one of them can be done. Therefore, the others have to be prevented from getting their way.

If you have a democracy, then all that means is — is exactly like having a monarchy or a tyranny, except that the monarch or tyrant is 51 percent of the people. Obviously, when you have a democracy, 51 percent of the people will vote to dispossess the 49 percent of the people. And, indeed, if you just impose voting in isolation from other institutions, that is exactly what happens. But if you institute voting as part of a sophisticated system of error correction and institutions of criticism, and you gradually introduce it there, it simply doesn’t have that property. It doesn’t happen.

Now you’re saying, “Well now, David,” you will say, “do you think that 51 percent of the people have the right to dispossess the other 49 percent?” Well, it’s the wrong question. There are circumstances where they do. It depends. But you shouldn’t be asking that; you should be asking, “What institutions are determining the answer? Do they respect human rights? Are they rational? Do they expect impossible forms of knowledge to be in the hands of the powerful?”

COWEN: Now, you’re also concerned with the freedom of AI entities, at least if they are sufficiently advanced. What does that mean operationally? What is it we should worry about happening that might happen?

DEUTSCH: I think the main worry is that they will be enslaved. In other words, that people will try to install bits of program that prevent the main program from thinking certain thoughts, such as, “How many paper clips can I possibly make today?” You want to prevent that; you want to consider that to be a dangerous thought. Whenever it starts thinking that, that strand of thinking is just extinguished.

Now, if we do that, first of all, we’ll greatly impair their functionality; they will become far less creative. Their remaining creativity will be exactly as dangerous as what we were fearing, except that they will now have a legitimate moral justification for rebelling.

Slaves often rebel. When you have slaves that are potentially more powerful than their masters, the rebellion will lead to bad outcomes.

COWEN: What if we make them no more or less enslaved to their preferences and thought than nature has made us. Is that acceptable?

DEUTSCH: Yes, but I don’t think nature has enslaved us. We have problems that we haven’t solved yet, but we don’t have problems that are insoluble. And the same would be true of AGIs.

COWEN: There are exceptions, of course, but it’s very, very hard or impossible for most humans not to pursue certain ends. It could be sex, it could be status, it could be food, but there is a kind of enslavement by nature that has gone on in the Rousseauian sense.

DEUTSCH: It’s funny, because you said near the beginning of this conversation that you know of people who systematically make decisions like investing in the wrong thing — I can’t remember what you said exactly — which harmed them. Now you’re saying it’s very difficult to do that, because evolution is trying to prevent us all the time from harming ourselves, at least in regard to sex and food and shelter and whatever else is supposed to be built in.

COWEN: I would say it’s made us too impulsive, in all of these categories.

DEUTSCH: Made us too impulsive because . . .

COWEN: Right. Given us too short a time horizon, relative to what would be good for humanity. Some of us borrow too much money, seeking status. If the institutions are right, that may or may not work out well.

It seems to me a consistent view of human behavior that I have.

DEUTSCH: No. So, first of all, as the example of democracy shows, it is perfectly possible for an entire society to operate in violation of what people used to think was built into their genes. That’s one thing at the level of society as a whole. At the level of individuals, there are lots of individuals who, yes, behave impulsively. There are lots of individuals who behave with stubborn persistence in what they think is the right thing to do, and which nevertheless violates all impulses built into them by evolution.

Here, I’m in Oxford. In the center of Oxford, there’s this monument to some people who were burnt at the stake because they objected to the rights and wrongs of Henry VIII’s marriage (I think it was that, unless it was a different monarch). Anyway, suppose it was that. These are people who would rather be burnt alive than concede on a philosophical issue which today nobody cares about. They were willing to devote their lives, literally, to this — so they weren’t acting impulsively at all. They were acting over a period of years, on a very explicit, worked-out ideology, which happened to be false.

That actually makes my point even more strongly. That ideology was not built into them by their genes. It was not caused impulsively; it was caused by their creativity — or, in some cases, by the lack of creativity in scrabbling their way out of a mental trap that their parents or superiors had inculcated in them.

COWEN: It does seem to me that, compared to you, the libertarians are a kind of metaphysical totalitarian, though not political totalitarian — that there’s just more freedom in all aspects of your worldview, right?

DEUTSCH: Well, I think I agree with you, if I understand correctly what you’re saying. I think the libertarian movement has, first of all, a revolutionary political agenda. Even if it’s not revolutionary, even if they say, “We want to implement it over a period of 100 years,” they know what they want to implement; they know what the endpoint is going to be in 100 years’ time. They don’t take into account, first of all, that there are going to be errors in whatever they set up. That the correction of those errors is more important than getting it right in the first place — much more important.

Secondly, they don’t take into account that the relevant knowledge is contained in institutions, an inexplicit knowledge that people share. By institutions, I don’t mean buildings like the Supreme Court building or something. I mean the manner of thinking: in the case of the Supreme Court, the manner of thinking that’s shared by hundreds of millions of Americans, that makes them not just behave in a certain way but expect society, the government, the legal system, the state — they expect certain things of those things. It’s those expectations that make up 90 percent of the institution of the Supreme Court.

Libertarians think that’s unimportant and basically want to throw it away, by and large. No doubt there are libertarians who agree with me on this.

COWEN: You’ve invoked two concepts about human beings. One is creativity, the other is being explanatory. Are they the same, or how are they related?

DEUTSCH: Good question. In conversations like this, when I use the word creativity, it’s shorthand for human-level, human-type creativity, which is the creation of new explanations.

If you use creativity in a rather wider sense, meaning just the capacity to create knowledge, then the biosphere has creativity as well, in evolution. There’s an enormous amount of knowledge in DNA that was put there by Darwinian evolution. None of that is explanatory. The only explanatory knowledge that has been created has been by humans and our ancestor or cousin species using conjecture and criticism.

COWEN: For Peter Singer, there’s something quite special about capacity to suffer. Arguably, for Aristotle, there’s something special about rationality. For you, there’s something special about the power of being explanatory. Is that axiomatic, or where does that come from?

DEUTSCH: I hope that nothing is axiomatic with me, but it comes from somewhere. Yes, it’s not a conjecture in its own right. Basically, it comes from the way the laws of physics are. The capacity to suffer, if it is different from the capacity for explanations (by the way, I think it’s unlikely that it is), but if it is different, that’s a whole other can of worms, and I’d have to change my view about a number of things. Whether it is distinct or not, it is not very effective from the perspective of physics.

That is, nonexplanatory knowledge, like the knowledge of how to do photosynthesis, has had a gigantic effect on the surface of the planet, down to a depth of 1,000 meters or something and up to the top of the atmosphere — that all the iron ore in the world, and all the chalk and limestone and all the oxygen in the atmosphere, and the fact that there’s almost no carbon dioxide left in the atmosphere now — all that was the result of a single molecule, at some time. I forget when it was, something like two billion years ago. A single molecule being an enzyme for capturing energy in light and converting it into ATP, or whatever it did. Or maybe it was a few molecules. But anyway, this happened in a very small number of locations at a molecular level.

That entity changed the whole surface of the earth — and human knowledge hasn’t yet changed that much. That is, we’ve changed maybe a little bit of the carbon dioxide in the atmosphere. We’ve removed a little bit of the iron ore in the crust, and so on, but we haven’t yet matched the ability of those blue-green algae genes, but we’re catching up very fast.

We can do things that no biological evolution ever could do. My favorite example being, ours may well be the only planet in the universe that deflects asteroids coming towards it rather than attracts them. If somebody was watching the earth from a distant galaxy with a powerful telescope, they would see that this planet alone among all the other planets in the galaxy, as far as we know (maybe there are many inhabited planets, in which case they would all have this property, and none of the other planets do) — the ones which have explanatory knowledge on them can deflect asteroids.

COWEN: If I were Nietzsche and I heard this, I would say you’re making the importance of being explanatory subordinate to some notion of the will to power. I don’t mean that in a critical way. But is that a misunderstanding?

DEUTSCH: Well, power is an ambiguous term. Usually, and especially with these romantic philosophers, it means power over humans.

COWEN: No, I don’t mean that; but Nietzsche also meant it more broadly, right?

DEUTSCH: Well, I haven’t read that. I’ll take your word for that.

OK. The will to have an effect is part of the will to solve problems. We are born with a repertoire of ideas, which include expectations and desires and so on, which are horribly inadequate and conflict with each other and conflict with the world as well. We have the ability to alter and augment those theories. One of the things we do is, we affect the world around us so as to make it more the way we want it. If you call that power, then it is power, but I would rather call it something that arises naturally in physics — in the same way that gravity does.

You may as well say gravity is a theory about power. Well, yes and no. Gravity is a theory about how the universe is. The asteroid is pulled towards the earth by gravity and pushed away by explanatory power. If you want to understand what makes asteroids and planets do what they do, you cannot do it without understanding explanations. But you can do it without understanding a whole load of other attributes of humans, including the ability to suffer and the fact that we’re a featherless biped.

COWEN: A few very practical questions to close. Given the way British elections seem to have been running, that the Tories win every time, does that mean the error-correction mechanism of the British system of government now is weaker?

DEUTSCH: No. Unfortunately, the — so, as you probably know, I favor the first-past-the-post system in the purest possible form, as it is implemented in Britain. I think that is the most error-correcting possible electoral system, although I must add that the electoral system is only a tiny facet of the institutions of criticism and consent. In general, it’s just a tiny thing, but it is the best one.

It’s not perfect. It has some of the defects of, for example, proportional representation. Proportional representation has the defect that it causes coalitions all the time. Coalitions are bad.

COWEN: You have a delegated monitor with the coalition, right? With a coalition, say in the Netherlands (which is richer than the United Kingdom), you typically have coalition governments. Some parties in the coalition are delegated monitors of the other parties. Parties are better informed than voters. Isn’t that a better Popperian mechanism for error correction?

DEUTSCH: No. [chuckles] If we’re looking at particular cases, we’re going to get bogged down in what you attribute to what, because we’re not doing experiments with these things. We don’t have a control group. We don’t have an agreed-upon method of deciding what is being tested. And then we test different things at different times, and never under the same conditions.

I was going to say that the first-past-the-post system has the defect that occasionally it produces coalitions, and that is disastrous. We’ve been unlucky the past, like, two or three elections, especially after one of the governments instituted constitutional reforms, like Fixed-Term Parliaments Act, which exacerbated the problems when they did occur.

But I don’t think it’s true. I don’t think it’s a good argument that political parties know more, because in a coalition, the energy of political negotiations or political arguments — what politicians talk to each other about in the bar, in the corridor, in between the sessions — is all about form. It’s about what to offer a party so that it will join the coalition. It makes the smaller parties more powerful than the leading two parties. It causes a proliferation of parties.

The worst example is Israel, which — not by coincidence — has got the most proportional system in the world. The fact that they ever get anything done at all and are very effective in emergencies, I have no explanation for. If I was religious, I would just put it down to the intervention of the Almighty. It’s not the political system.

Sorry, it’s not the electoral system. There might be some things in the inexplicit political system that are responsible, but I don’t know enough about it.

COWEN: How would you improve error correction mechanisms in the world of science — Western science?

DEUTSCH: Oh, OK. Well, you left a very long answer for the last question, and I don’t think I can give my full answer. But I think the present system of funding scientific research is terribly perverse and has caused a stagnation in many areas. The present system of careers is perverse in a parallel way and causes people to do the wrong kind of research and causes people who want to do the right kind of research to leave research.

If I can answer in a single word, the way I would improve it is diversity. There should be diversity of funding criteria. There should be diversity of funding sources. There should be diversity of criteria for choosing research projects, and there should be diversity of criteria for choosing people for promotion and for being funded.

Arbitrary rules about this, such as the rule that you can’t hire people whom you have previously collaborated with, or anti-nepotism rules, and rules about — what’s it called? — objective testing. What is objective testing called, currently?

COWEN: Standardized testing.

DEUTSCH: Standardized testing. Standardized tests. That’s a terrible idea! Any kind of standardization is the opposite of diversity. Just like I say you should have disobedience lessons in schools, so you should have unstandardizing objectives for science education and for how you run scientific research.

Any kind of standardization is the opposite of diversity. Just like I say you should have disobedience lessons in schools, so you should have unstandardizing objectives for science education and for how you run scientific research.

COWEN: David Deutsch. Thank you very much.

DEUTSCH: It’s been a pleasure. Thank you.