00:00:00.000 Hello, David Deutsch, are you on the other end there?
00:00:06.680 It's great to have you here on Blogging Heads, David.
00:00:10.360 Let me just introduce myself and then I'll let you do the same.
00:00:14.560 I am John Horgon, I'm a science journalist and occasional science correspondent for Blogging
00:00:20.040 Heads TV and I have a really special guest with me today.
00:00:24.680 The physicist, British physicist, David Deutsch, who is now in your end Oxford right now.
00:00:32.720 So, David, could you just give us a little background on yourself and then we'll start
00:00:43.080 So, my name is David Deutsch and I'm a physicist at Oxford University and I'm the author
00:00:49.840 of two books, the fabric of reality and recently the beginning of infinity.
00:00:55.680 David, you were often described as a pioneer of or even the father of quantum computation.
00:01:13.640 Can you just describe a little bit about how you got into that field?
00:01:16.840 I wish I think was quite a while ago, a couple of decades ago.
00:01:20.240 Yes, it was actually, I actually began thinking about quantum computers in the 1970s, although
00:01:27.520 I didn't call them that then because I didn't think of them as being anything to do with
00:01:38.120 The context there was the so-called parallel universes or many universes interpretation
00:01:44.440 of quantum mechanics and I had realized that the consensus view that both the proponents
00:01:54.440 and the opponents of this rather controversial interpretation had been taking, namely that
00:02:01.920 it is just a matter of interpretation and that there are no possible experimental tests
00:02:07.280 of it, was actually false and that this idea that it can't be tested was simply due to
00:02:16.320 some poor thinking about what would happen when an observer did a measurement on another
00:02:25.360 And so I was trying to clarify this issue of what an observer is in quantum mechanics.
00:02:33.560 And so I thought, well, the simplest way to clarify that is to imagine an artificial observer
00:02:41.880 and what would be called an AI or an AGI, an artificial general intelligence, but running
00:02:51.400 Of course, all hardware obeys quantum mechanics, but I was thinking of hardware that obeys
00:02:57.280 it in a way that can be tested in the laboratory.
00:03:01.560 And so I imagined an AI program running on this quantum hardware and then I added a few extra
00:03:11.720 elementary operations to this computer, which would be, sorry, that was okay, they'll have
00:03:21.800 It's okay, it's those little glitches that make blogging head so charming to some people.
00:03:33.800 So I had to add a couple of extra operations to this computer because that's what made
00:03:42.520 the difference between doing this experiment with a computer that obeys quantum mechanics
00:03:46.440 and an ordinary computer, the kind of computer that we know that we're familiar with.
00:03:52.440 And given those extra operations, it was possible to perform an experiment whose outcome
00:03:58.600 would be one way if there was only one universe, if something like the Copenhagen interpretation,
00:04:05.560 the way function collapse interpretation, or any single universe interpretation of quantum
00:04:13.120 It would go another way if the many universes interpretation was true.
00:04:19.280 And so as a sort of side effect of this, I realized that quantum mechanical computers would
00:04:29.520 be inherently more powerful than they could perform more qualitatively different computations
00:04:38.960 And then later, yes, maybe you should just back up and we can't assume that our listeners
00:04:49.040 are completely familiar with all the different interpretations of quantum mechanics.
00:04:54.360 Just remind us of what the many worlds or many universes interpretation of quantum mechanics
00:05:01.400 is and how it differs from, say, I don't know, the Copenhagen interpretation, if that's
00:05:07.840 kind of the more mainstream view of what quantum mechanics means.
00:05:15.120 To explain what quantum computers are, I have to explain what quantum mechanics is from my
00:05:22.640 And I adhere to what's called the parallel universes or many universes interpretation proposed
00:05:28.800 by Hugh Everett in 1957, it says that the universe we see around us is just a tiny facet
00:05:39.520 of the whole of physical reality, which, and so if we want to retain the same word for
00:05:44.920 universe, we have to invent another word for the whole thing and I favor the word multiverse
00:05:53.240 In my view, and in the view of its proponent, its other proponents, this is an incontrovertible
00:06:03.240 implication of quantum theory, which is almost fundamental theory in physics.
00:06:09.440 But I always have to warn the viewer immediately that this view is shared by perhaps fewer
00:06:17.160 than 10% of theoretical physicists at any rate, that's what I take quantum theory to say.
00:06:28.480 And quantum computers are computers that harness quantum theory to perform a different mode
00:06:38.280 of computation, something that cannot be performed by existing classical computers at all.
00:06:45.960 I see, okay, I want to come back to multiverse theories and the multiple universe interpretation.
00:06:59.720 Now I'm holding up the galleys that I got from the Wall Street Journal when I reviewed
00:07:06.640 your book, the beginning of infinity, and I should say that the journal, I think, asked
00:07:14.760 me to review your book because it is almost the antithesis of a book that I wrote in 1996,
00:07:25.240 And in fact, at the very end of your book, you mentioned my book and reject its claim
00:07:32.840 that science might be approaching its limits very forcefully.
00:07:37.000 I think the journal expected me to lay waste to your book, they thought that that would
00:07:42.160 be entertaining, and I fully expected to do that when I started reading you, but I ended
00:07:49.400 I think it wasn't what I expected at all, it's a really grand vision of human possibility
00:07:58.200 and it got me questioning my own pessimism about the future of science and even technological
00:08:08.160 So could you just tell us, where did the idea for this, first of all, say give us a nutshell
00:08:16.960 version of the book's theme and then and also say give us some sense of where the ideas
00:08:25.680 Yes, the basic theme of the book is that all human progress in the past has been fundamentally
00:08:36.240 caused by a single kind of activity, which I call the quest for good explanations, explanations
00:08:44.840 being accounts of some kind of reality and how it works and why.
00:08:53.840 And pursuing this theme of what an explanation is, why the quest for good explanations
00:09:05.000 It makes contact with the whole lot of other bits of science and philosophy and so on,
00:09:11.800 which together imply that this process need never come to an end.
00:09:18.040 That is, we could bring it to an end if we destroy ourselves or decide not to or whatever,
00:09:23.400 but there are no inherent limits to the growth of knowledge and therefore to progress.
00:09:30.280 And by the way, you mentioned your review of my book, I thought it was exceptionally nice,
00:09:35.480 generous review, but it's funny, you should mention your feelings on reading it because
00:09:41.680 they were exactly mirrored in my feeling on reading your book.
00:09:46.080 I was expecting to hate everything in it, but instead, I merely disagreed with the conclusion.
00:09:53.400 It seemed to me, correct me if I'm wrong about this, but it seemed to me that in every argument
00:10:00.120 in your book, there is a sort of reluctance, there is a wish that it will otherwise and
00:10:07.240 that your arguments about these limits, you are forced to them because you think that
00:10:14.760 that is the logic of the situation, but you would rather that it will otherwise.
00:10:23.840 Well, of course, I mean, I became a science writer because I see science as I think you
00:10:31.000 do as by far our most powerful way of understanding ourselves and understanding all of reality.
00:10:39.880 And as we got into science journalism in the early 80s, when there was talk of a theory
00:10:45.480 of everything, Stephen Hawking had predicted the end of physics, there would be this great
00:10:50.120 revelation at the end of our quest to understand everything.
00:10:57.040 And I was enormously disappointed when I went after a period of time, I started suspecting
00:11:04.440 that maybe science was already bumping into walls and we wouldn't get these great
00:11:16.680 But I think these walls of our own making, they're not inherent in the subject of, I mean,
00:11:23.800 this is my subject, the book covers all subjects and by the way, not only science, I think
00:11:29.000 this thing about the quest for good explanations has been responsible for all progress
00:11:34.840 such as moral progress, political progress, artistic progress, every kind.
00:11:40.840 But science is my field in physics in particular and it is true that progress in fundamental
00:11:48.160 physics was reached an all-time high in the early 20th century.
00:11:55.880 And although it hasn't, it by no means gone to zero now, it is lower now than it has been
00:12:05.280 And this is caused some people to think that we may be running out of either, we may
00:12:12.960 be reaching the end as you, I mean, in your book, you give both possibilities, either
00:12:17.640 we're reaching the end of knowledge so that we'll understand everything or we're reaching
00:12:23.320 the end of the capacity of science to create knowledge.
00:12:30.280 And either way, we're heading for a brick wall.
00:12:32.880 Now, I think this apparent brick wall, as always in the history of knowledge, was not caused
00:12:41.520 by anything in the subject, it was caused by what people have chosen to do.
00:12:49.720 And you mentioned the theory of everything, to me, which is the theory of all, a proposed
00:12:56.840 or hoped for theory of all elementary particles, space, time, and gravity, that theory,
00:13:08.680 to me, it should not be called the theory of everything.
00:13:12.080 That is a very tiny facet of physics from my perspective, let alone everything.
00:13:19.640 It's just the theory of how objects behave, but beneath all such theories are formulated
00:13:31.200 within a certain profoundly significant language and conceptual framework, namely quantum
00:13:39.640 theory, and the theory of everything just assumed that quantum theory would survive would
00:13:48.840 be exactly the same theory after we have discovered this great unification.
00:13:53.680 And also that, essentially, the theory of gravity also would, and that unifying them would
00:13:59.400 simply be finding a way of writing either of them in the language of the other.
00:14:05.480 And that has been the technique of elementary particle physics for the past several decades.
00:14:11.840 And to me, that is simply what they're doing is they're trying to formulate a classical theory,
00:14:18.960 not counting quantum mechanics, as if it was all in one universe, as if they weren't interference
00:14:25.080 phenomena and tunneling and all those things, just a classical theory, and then they apply
00:14:31.920 a process that physicists call quantization, which is a way of transforming a classical theory
00:14:38.920 into a quantum theory. And so you turn the handle, it's just a mechanical process.
00:14:44.960 And this worked for electro dynamics. That was the great achievement of Richard Feynman
00:14:52.400 and Julian Schwinger and others. And it really hasn't worked since. And I don't think
00:14:59.600 there's any reason to believe that this process will ever work. Again, it was just a stroke
00:15:04.760 of luck that quantum electro dynamics can be obtained from classical electro dynamics by
00:15:10.880 a mechanical process of quantization, plus a whole load of cleverness. But I don't see
00:15:17.520 I assume that that would lead you to be skeptical of string theory and even loop space
00:15:26.320 theory and some of the main contenders for a theory that could unify relativity and quantum
00:15:33.920 Unfortunately, although I wouldn't say these things aren't worth doing that because if
00:15:39.360 nothing else, we learn from them even when they fail. But it seems to me that progress,
00:15:46.520 because progress comes from good explanations, it has to come from problems because an explanation
00:15:52.640 is an explanation of something like how a thing can possibly be. And that means that the
00:16:02.520 prevailing way of trying to find fundamental theories in physics is unlikely to succeed
00:16:09.360 because it is looking for mathematical models and then trying to understand what that could
00:16:20.680 And I mean, even if you found the right theory that way, I think there are chances of fairly
00:16:25.360 low that you'd recognize it because how do you know which of those mathematical objects
00:16:31.340 correspond to which objects in nature? We're assuming that the future theory is going
00:16:38.000 to still be based on things like particles, space, time, fields, and so on. But why should
00:16:45.160 Fundamental progress in the past has always involved new kinds of entity, new modes of explanation
00:16:55.400 that weren't thought of before. So yes, I'm skeptical that these approaches, any of
00:17:02.220 these approaches can work. And I think that's why there hasn't been this fundamental
00:17:07.580 David, let me raise an objection to your optimistic vision of the future of science, which
00:17:16.200 is actually based on my reading of what quantum mechanics is done in physics. You have a
00:17:25.240 passage in your book where you recall, I think it's Niels Bohr saying that anybody who
00:17:30.400 thinks he understands quantum mechanics obviously doesn't. And you reject that as a kind
00:17:36.720 of no-nothing-ness, which is surprising for something like Bohr. But it seems to me that
00:17:40.960 if you look at sort of in a sociological sense, all the different competing attempts to
00:17:47.800 understand what the hell quantum mechanics means, that you'd have to grant that even for
00:17:53.440 the experts, the theory is quite confusing. On the other hand, it's powerful. It doesn't
00:18:02.040 anything that you could want from a theory in terms of being able to predict experiments
00:18:06.920 and leads to all sorts of amazing applications and so forth. And so it seems to me that
00:18:12.200 you're getting a split between science as giving us power over nature and science as
00:18:20.400 a mode of understanding. And the understanding, and especially then, if you look at the
00:18:26.360 rest of physics as well, which has become for the average person extremely difficult
00:18:31.800 to understand, very esoteric, I see science as really beginning in the 20th century becoming
00:18:39.720 more and more distant from the comprehension of the average person. And I just wonder where
00:18:51.760 your optimism comes from that somehow in the future, I don't know, as a result of new ideas
00:18:58.680 and physics, new ideas about how unification should take place or whatever, why we should
00:19:04.720 get the comprehension that seems to be received now in the past.
00:19:11.240 Yes. In my view, this split that you talk about between quantum theory as a powerful technique
00:19:20.480 for building things and making predictions and quantum theory as a way of understanding
00:19:28.160 nature. This split is not a feature of quantum theory. It is a feature of the sociology
00:19:34.240 of science during the 20th century. The split was introduced as a matter of philosophical
00:19:40.800 dogma in order to protect from criticism the bad explanations that the founders of the theory
00:19:51.120 and subsequent physicists have favored for quantum theory, which by the way from the
00:19:57.160 many universities point of view, they are all equivalent to saying, well, at some point
00:20:03.280 when we're not looking, all the universes but one suddenly disappear. And we can't notice
00:20:10.480 this because we're not looking. And that sort of thing. And when the response to careful
00:20:19.400 considered criticism of this view is to say, oh, well, you don't understand quantum
00:20:24.680 theories. Now, the thing is we've been here before that as the, however, the founder
00:20:32.480 of the many universities theory pointed out in a famous letter, we have been here before
00:20:40.280 the a radical change in worldview was occasioned by the discovery of the heliocentric theory
00:20:49.000 that the son and not the earth is the center of the solar system, what we now call the
00:20:54.600 solar system. And Galileo championed this theory and in a famous conflict between him and
00:21:03.800 the inquisition, they tried to force him to renounce the theory. But if you look in more detail,
00:21:11.320 what they were asking him to renounce was not the power of the theory, not its ability
00:21:16.720 to predict that they were quite willing to allow him to, to espouse and to teach and
00:21:22.880 and so on. What they wanted him to reject was the claim that this described reality,
00:21:30.880 that this described the solar system. And the new vision of the solar system that was
00:21:37.400 entailed by the heliocentric theory was a jarring change from what had gone before,
00:21:44.920 because for example, it meant that the earth beneath our feet, which is the paradigm of
00:21:52.480 something fixed in common sense, is actually moving very fast. It's moving at a thousand
00:21:59.440 miles an hour around the earth's axis and also moving around the sun. And we can't
00:22:06.920 feel this because the laws of physics are constructed in precisely such a way as to cancel
00:22:13.480 out any feeling that we might have about this motion. And people who were at first sight,
00:22:20.880 this is a ridiculous idea, because it's like what Lewis Carroll said. I was thinking
00:22:28.640 of a plan to die one's whiskers green and always use so large a fan that they could not
00:22:34.240 be seen. It was accepting one thing just in order to make it invisible and then explain
00:22:40.720 something else and so on. And it's only when you look very carefully at what the theory
00:22:44.840 says that you see how much and how enormously better an explanation it is of the observed
00:22:53.400 motion of the planets and so on. And then it allowed further unification by Newton of celestial
00:22:59.760 mechanics and terrestrial mechanics and so on. And so this split at that time was an invention
00:23:08.560 of the Inquisition. The split in quantum mechanics regrettably was an invention of its
00:23:16.160 very founders. They didn't want to take the theory seriously as a description of reality.
00:23:22.920 Do you think that Einstein, if he was alive today or had lived long enough to see you
00:23:30.760 ever its theory, would have been embraced it or would have made it even more frustrated
00:23:37.920 with quantum mechanics and convinced that it had to be incomplete or wrong in some way?
00:23:44.040 It's hard to predict what an actual person would have said. But if we look at what Einstein
00:23:49.640 wrote about quantum theory and wrote about his famous criticism and his great debate with
00:23:56.240 Neil's Law about quantum theory, all his criticisms are straightforwardly met by the
00:24:03.040 many universities interpretation. So he only missed it by two years and it's very very
00:24:08.600 frustrating. The bristy wit in his famous article introducing the many universities interpretation
00:24:17.520 in a footnote he says that Albert Einstein would surely have liked this.
00:24:24.680 So I think he would as well because what was driving Einstein both in theory of relativity
00:24:33.720 and in his critique of quantum theory as it was in his day was realism. He understood
00:24:41.520 science and physics as being the study of what reality is like. And these equivocations
00:24:50.040 that the quantum theory appeared to bring namely, well what do you really mean by real
00:24:56.760 and we can't really say well it's real, we can only say what we observe about the reality
00:25:01.160 and so on in which case science becomes the study of us, it becomes the study of our perceptions
00:25:09.560 and everything else is just a sort of fiction. That he rejected rightly. Having, by the
00:25:16.320 way, believed stuff like that in his youth and rejected it in order to make progress with
00:25:22.880 relativity. He then applied that idea of realism to the whole of science and insisted on
00:25:29.640 that and rejected the quantum theory of the time as not being realistic whereas the
00:25:39.600 ever theory is entirely realistic. In fact, you can define many universe quantum theory
00:25:46.680 as just the statement that the equations of quantum mechanics describe reality. That's
00:25:52.720 all it is. Let me bring up another possible objection that Einstein might have had. Einstein
00:25:59.760 has this wonderful phrase. I have no idea when he said it but that the goal of physics
00:26:06.440 is to determine whether God had any choice in making the universe. It's a way of getting
00:26:13.800 up the question of why do we, okay even after we figure out the laws of the universe
00:26:19.160 in its history and so forth, we still have to ask why this universe? Why do we find ourselves
00:26:24.680 living in a universe that allowed our existence and so forth? It seems to me that, and there
00:26:31.000 is a hope, Stephen Weinberg has also talked about this, that there would be a theory at
00:26:37.320 some point that would be kind of logically inevitable or necessary and if you tried to tweak
00:26:47.000 it, it would fall apart and it would make this universe that we live in also necessary
00:26:54.440 or inevitable in some sense and what has happened over the last couple of decades is that
00:26:59.280 things have gone completely in the opposite direction and now you have theories that predict
00:27:05.680 basically an infinite number of other universes. So you're sort of back to the arbitrariness
00:27:12.560 of this one and the problem as far as I can tell, it's gotten even worse. So I wonder
00:27:20.240 how you respond to that issue. So first of all, if one interprets Einstein's view as
00:27:28.720 that quote of Einstein as saying that we need an ultimate explanation, then I think that that
00:27:36.560 is a chimera. I think that that will never be found and can never be found and if such a thing
00:27:44.160 could be found it would be a catastrophe because it would be the end of progress. The progress
00:27:53.680 in science is intimately connected with all the other kinds of progress so it would also lead
00:27:59.520 to the end of progress in the other ways that we like such as morality, politics and so on.
00:28:05.120 But I think there is nevertheless a truth in it which is the truth about good explanations.
00:28:11.440 What we want from a good explanation in the way I describe in the book is that it be hard to vary.
00:28:20.560 That is, if you displace one note as Sharper said in the play Amadeus, then there's diminishment
00:28:31.440 and if you displace a phrase then the whole structure falls apart. So in that sense we want the
00:28:36.880 theory to have a good theory must have a certain inevitability about it with hindsight of course.
00:28:43.760 So with hindsight you see there couldn't have been any other way. But what saves us from the evil
00:28:51.600 implications of an ultimate explanation is that good explanations solve the problems that they address
00:29:02.640 but they always raise new and better problems. So the problems that we have today for example
00:29:10.080 in cosmology about what the dark energy is that's making the universe expanded in accelerating
00:29:16.800 rate and one of the most startling discoveries of science in recent times,
00:29:22.960 that discovery depended on the previous discovery of the general theory of relativity
00:29:29.920 and cosmological models in that theory and so on. It's only in the light of those theories
00:29:36.240 that we can even know that the expansion of the universe is accelerating and know that that's
00:29:43.200 amazing. So in solving the problems that Einstein solved, namely how things like the motion of
00:29:52.080 light and the existence of gravity could be reconciled in his general theory of relativity,
00:29:58.160 that opened up problems that were simply inconceivable before and one couldn't have expressed
00:30:04.400 them even in the language of of physics or in the language of common sense. There were problems
00:30:10.000 whose that opened up because of the solution of previous problems and that is
00:30:17.360 that's the solution to the conundrum. How we can get our hard to vary good explanations
00:30:26.160 without grinding to a halt as a result. It's because good explanations open up new problems.
00:30:34.880 Let me bring up another figure he's very prominent in your work, the philosopher Karl Popper,
00:30:42.960 who I was fortunate enough to interview a few years before he he died. Obviously he's been
00:30:49.840 a very big influence on you. I just wonder how Popper would have reacted or did react. I
00:30:59.920 don't know if he ever wrote on multi-verse theories, but wouldn't I would suspect that Popper
00:31:08.000 would have been a skeptic of multi-verse theories because he was so insistent on
00:31:14.080 testability and it seems to me that multi-verse theories are at the very least extremely
00:31:24.560 difficult to test and that any kind of evidence you would have of their existence would be
00:31:29.760 circumstantial at best. Okay, yes, two issues there. One about the testability of the many
00:31:41.280 universe interpretation and the other one about Popper. I was also privileged to meet Popper on one
00:31:47.040 occasion when I was a student and I was lucky enough to be invited along to a meeting between
00:31:54.240 Popper and my mentor Bryce Dewitt, my physics boss, Bryce Dewitt and basically at that meeting,
00:32:03.360 Dewitt told Popper that he had misunderstood what the fundamental problem is in quantum theory.
00:32:09.760 The Popper thought it was to give a meaning to probability statements and he'd kind of missed
00:32:17.120 the deeper problem of things like entanglement and interference and the measurement problem.
00:32:27.200 And Popper said that he had realized that he had an inadequate understanding and had held up
00:32:35.440 publication of one of his books in order to try to improve it. Now, I've looked at his subsequent
00:32:40.720 books and they all contain the same misunderstanding of quantum theory, unfortunately.
00:32:46.720 When he does, he does occasionally mention the many universe interpretation but only to dismiss it
00:32:52.160 for kind of non philosophical reasons just to say, well, you know, we can't have that and therefore
00:32:57.120 I'm going to concentrate on this other thing. So Popper unfortunately like Einstein died too soon
00:33:05.920 but not too soon chronologically. He just died too soon for the right understanding to have reached
00:33:12.080 him. I suppose that is not a coincidence either because 90% of the physicists whom he might have
00:33:20.960 asked about the foundations of quantum theory would have given him nonsensical answers. Now,
00:33:27.600 as for the testability of the many universe interpretation, this is, as I said, there are
00:33:39.200 in principle tests that would test it against the rival theory that there is only one universe.
00:33:46.160 But really that is grossly understating the scientific status of the theory. The reason that one
00:33:56.800 doesn't normally test an interpretation, normally in science, one says that yes, indeed,
00:34:03.360 the equations of the theory do describe reality and it's really only in the case of quantum theory
00:34:08.640 within physics that somebody has said, how can we test the interpretation by itself? Namely,
00:34:16.560 how can we test the statement that these equations, though we're not disputing that they correctly
00:34:24.240 predict experiments, how can we test the statement that in fact they represent reality rather than
00:34:30.240 just what we see in reality. As I said, we've been here before in physics, namely at the time
00:34:40.000 of Galileo and the Inquisition, but in the present day there is a very close analog of this and
00:34:48.240 that is the creationists who say that fossils, no one's ever seen a dinosaur, just like
00:34:55.520 no one's ever seen in parallel universes, all we have is the circumstantial evidence of fossils
00:35:01.760 and the interpretation of fossils as being the remains of dinosaurs. Similarly,
00:35:10.640 we have no one's ever seen parallel universes, but what we have seen is interference phenomena
00:35:17.520 and the interpretation of interference phenomena as being due to the interaction of different universes
00:35:25.680 and there's no other explanation. So if you want to say the other universes don't exist,
00:35:30.480 you have to do it by fear rather than rather like the people who say that the world was created
00:35:35.280 6,000 years ago with fossils. So similarly, the conventional interpretations of quantum mechanics
00:35:42.240 say that at the moment of a measurement, all the universes except one disappear, don't exist
00:35:50.080 and no one can contradict this because no one can see them. David, I'll just tell you,
00:35:56.080 I think that's a stretch to compare doubters of parallel universes to, and I count myself one,
00:36:04.400 not a doubter, but more an agnostic if someone who thinks that it's kind of a mood issue
00:36:09.120 because we'll never have good evidence, doubters of these things to creationists who are sure
00:36:15.680 that dinosaurs really exist. But listen, I want to get onto another really big topic that you
00:36:22.720 raised in a book. By the way, I was only saying that the logic is the same. The psychological
00:36:28.640 motivation is not the same, but the logic is the same because of the existence of good
00:36:34.560 explanations in both cases, but okay, continue. All right, a really wonderful theme that emerged
00:36:43.680 at a number of places through your book was, and I'll put it in my own words and you can tell
00:36:49.760 me if I've gotten it wrong, was a kind of critique of simple reductionism or materialism,
00:36:58.800 which obviously is the kind of prevailing philosophy of physics that good answers will come
00:37:08.640 from going to smaller and smaller scales and also focusing on things, on objects, on particles
00:37:15.920 and so forth. Yes. And you seem to be, you are, to my mind, saying that that is a much too
00:37:25.600 restrictive form of explanation and that we have to recognize that what we might even call
00:37:33.040 immaterial phenomena that aren't reducible to specific physical objects or processes
00:37:40.480 can have a profound impact and have had a profound impact on reality, particularly our human
00:37:47.680 reality, human history, the world of politics and culture and so forth. And it seems to me,
00:37:56.480 you're almost, it's almost a rebuke of physics as kind of the really the best mode of understanding
00:38:07.360 the world. And you're emphasizing how important mind is and ideas are and thoughts and so forth.
00:38:16.080 So I'll talk about that a little bit. Yes, of course I am a physicist and I'm profoundly
00:38:23.360 opposed to any idea of non-physical explanations that contradict physics. So that's a no-no
00:38:34.160 and really doesn't make sense. However, there are ways in which both emergent properties,
00:38:43.200 such as minds and life and so on have an effect. And as you said, also abstractions.
00:38:49.920 Now this, this, the fact that the theory of good explanations led to the idea that abstractions
00:38:56.560 are real things was slightly surprising to me. I wasn't expecting the link, at least,
00:39:04.560 wasn't expecting it to be so strong as it is. But the thing is if you think about how to explain
00:39:10.560 events, physical events, like a footprint on the moon, how do you explain how that happened? Well,
00:39:23.120 it happened because of human ideas, of science. And human ideas, you could say in this reduction
00:39:32.400 it's sense that as you rightly say is the prevailing mode of explanation and the prevailing
00:39:39.680 idea is to look down on other modes of explanation that those ideas are nothing more than
00:39:46.640 configurations of atoms. So some physicists, some rocket scientists put their brain into certain
00:39:55.520 configurations of atoms and those atoms then acted on other atoms, which acted on other atoms,
00:40:00.240 which then ended up making a footprint on the moon. Now what that misses is the explanation of
00:40:08.080 why certain configurations of atoms put footprints on the moon, while others, the overwhelming
00:40:15.600 majority of configurations that human brains, even human brains have been put into in history,
00:40:22.640 do not have that effect. And it's because of, it's a certain type of information. And this
00:40:28.640 information can't, in my view, be reduced to statements about atoms, because if you think about
00:40:39.120 what that information does, it is in brains, but it's the same information then gets transferred
00:40:45.120 into, let's say, sound waves in air and then it gets transferred into
00:40:50.160 ink and ink on paper and then it gets transferred into magnetic domains inside a computer,
00:41:03.280 which then control the machine that instantiates those ideas in bits of steel and silicon and
00:41:09.840 so on. And so on, there's an immense chain of instantiations of the same information.
00:41:17.840 And it's only special kinds of information that have this property that they are preserved and
00:41:25.920 instantiated in successive physical modes. So what is being transmitted, what is having the causal
00:41:35.280 effect is not the atoms, but the fact that the atoms are in certain instantiate certain kinds
00:41:46.720 of information and not other kinds. So therefore, it is the information that is having the causal
00:41:52.800 effect. If a particular instantiation of that information were damaged, then processes would come
00:42:00.080 along to fix it, whether or not they could fix the physical instantiation. For example,
00:42:05.680 if the computer goes wrong, then we don't use the corrupted information. We go back and rescue the
00:42:13.520 information from a different computer and we throw away the atoms that at one point instantiated
00:42:19.680 it. So the information causes itself to remain in existence. Now, I think there's no way out
00:42:26.880 of that mode of explanation. And if explanation is going to be the fundamental thing about
00:42:34.080 our criterion, for example, about what is or isn't real, then we have to say that information
00:42:38.960 and this particular kind, which we call knowledge, is real and really does cause things.
00:42:47.280 It seems to me, you've got you bring up the word choice at a number of places in your book and you
00:42:55.440 emphasize the power of human choice. It seems to me that what you were really doing is defending
00:43:04.720 the concept of free will. Maybe you can tell me if I'm wrong here. And as some of the listeners
00:43:15.280 out there know, I am a free will fanatic. I'm very upset that some prominent scientists recently
00:43:24.800 have said that free will probably doesn't exist. It's an illusion. Stephen Hawking
00:43:31.200 has said as much Einstein in a couple of his quotes suggest that free will probably doesn't
00:43:40.480 exist. So you believe in free will, I take it. I certainly do. And I think that the argument
00:43:49.680 against free will from reductionism is just a mistake. It's a fundamental mistake. It's the idea
00:43:59.600 that all explanation must be in terms of microscopic things. There's no philosophical for
00:44:09.600 argument in favor of that, that I'm aware of. It's just an assumption. It has historical roots
00:44:15.360 in how science centuries ago escaped from the clutches of the supernatural. And as I said earlier,
00:44:24.560 certainly I'm opposed to any kind of modes of explanation in terms of things like, in terms of
00:44:33.600 immaterial things, in terms of abstractions that contradict physics. But the idea that all such
00:44:40.320 explanations by their very nature contradict physics is simply false. I just gave an explanation of
00:44:47.120 footprints on the moon in terms of the ability of certain types of information to preserve
00:44:53.920 themselves in existence and so on, whereas other kinds don't. That I defy anyone to reproduce
00:45:01.440 in terms of atoms. And I also define anyone to show how that contradicts an explanation in terms
00:45:06.960 of atoms. So we have to accept the physical world as we find it. We have to find the best
00:45:15.360 explanations that explain it rather than impose by dogma a criterion that explanations have to
00:45:23.440 meet other than that they explain reality. So I think this, this reductionism, the fashionable
00:45:31.120 reductionism is just a mistake. I'm sure that free will exists. However, I think free will is one
00:45:38.320 of a constellation of emergent abstract. We're not sure exactly what proportion the free will is
00:45:47.600 abstract or emergent properties that are not yet understood. Things like consciousness,
00:45:56.800 creativity, choice, free will and so on. We do have good explanations about them at the emergent
00:46:06.000 level, but we don't understand them well enough to make artificial ones. And I say in the book
00:46:14.720 that my criterion for judging any theory of consciousness, free will and so on is can you program it?
00:46:26.160 And if you can't program it, then I cannot take seriously your theory of it. Now, I don't have a
00:46:33.120 theory of it. I only have a theory that it exists. Now, if someone says that it doesn't exist
00:46:39.360 because we can explain everything without invoking it, I want to see those explanations.
00:46:47.360 Roger Pedros, I assume that you know him has proposed a solution to the mind-body problem
00:46:59.040 involving quantum mechanics working in some way. To me, this is the mind-body problem and free will,
00:47:08.800 which is obviously a big part of it, is the biggest, the biggest unsolved problem in
00:47:15.600 in science. And people are just grasses on right now. So I just wonder if you see any even blue sky
00:47:22.560 ideas that might provide a kind of framework for understanding it. Maybe also information theory,
00:47:29.040 which some people have also tried to bring into physics. Well, as you said, Roger Pedros is
00:47:36.880 looking for a new theory to replace quantum theory, which would not only
00:47:44.960 be a better theory in physics than quantum theory is, but would also solve problems like
00:47:51.120 the existence of free will and creativity and so on. I'm pretty skeptical for the same reason
00:47:56.560 that I'm skeptical of the mathematical approaches that are currently fashionable in fundamental
00:48:00.720 physics. I think that one solves problems in physics by addressing problems that are in physics,
00:48:07.040 rather than hoping that they have certain attributes, finding a theory with those attributes,
00:48:13.360 and then hoping that it applies to physics. But you know, I could be wrong, but at present,
00:48:19.600 there are no such theories. I think existing approaches to AI, artificial general intelligence,
00:48:32.240 are all philosophically flawed. And I think that's why they haven't succeeded for decades
00:48:41.760 because a philosophical advance is needed. And they are trying to get the answer without making
00:48:54.480 any philosophical advance. And that leads them essentially to sort of behaviorist models of what
00:49:05.760 and behaviorist models are non-explanatory models. They are models that just try to relate output
00:49:10.880 to input without explaining why the output comes from the input and so on. And I think that
00:49:17.760 that approach can't succeed. And it's the reason that the quest for AI has not got anywhere
00:49:24.240 during the last decades. What we need is first philosophical progress in understanding
00:49:32.480 how creativity, I think that's the key thing that relates all these unsolved problems about free
00:49:44.640 will, consciousness, and so on, how creativity is implemented. And it has to be implemented,
00:49:53.840 we know a few things. It has to be in the broadest sense, an evolutionary process. It has to
00:50:03.440 work by variation and selection, or as publicals it in the case of science, conjecture and
00:50:10.240 refutation or conjecture and criticism. But we need to know the details and devil will be in
00:50:16.480 the details. My guess is that once we understand what it is, we will be able to program it.
00:50:26.000 I think there's an analogy here with Darwin's theory of evolution that Darwin's great contribution
00:50:35.120 in my view is not his scientific theory of evolution. It is the philosophical progress that he made
00:50:42.160 in inventing a new mode of explanation, just not just a new explanation, but a new mode. Previously,
00:50:50.800 everyone who addressed the question, why are animals the way they are? Why are they, why are
00:50:58.720 they adaptations there? Everyone who, people try to address this by supernatural explanations and
00:51:07.520 also by scientific explanations, but all of them took for granted that what you had to do
00:51:13.920 is find a reason why there are elephants, why elephants have long trunks, that kind of thing.
00:51:22.160 And Darwin realized that that is a bad way of approaching the problem. To understand why
00:51:29.120 elephants have long trunks, you must not ask why they have them as your initial question,
00:51:34.800 you must ask what kind of process could give rise to trunks. And then that they have purposes and
00:51:44.960 some biological features have purposes, some have anti-purposes like the peacock's tail and so on,
00:51:50.880 that all comes out in the sophisticated elaboration of the basic theory of how it could possibly
00:51:58.080 happen by variation and selection, by random variation that is undirected variation and then directed
00:52:07.760 selection. Now, free will, consciousness and so on, definitely involves that as well,
00:52:16.320 but it involves something else that we don't get to understand, which it will take a new Darwin
00:52:21.280 to realize. And once the new Darwin has realized it, it will be, well, it took many decades
00:52:29.840 between Darwin and DNA. I think it will be much faster. It will be in between the person who
00:52:38.800 discovers the correct philosophy of AI and the programming of AI will be a matter of months
00:52:46.800 not decades. I hope I live long enough to see that. And I also, it would be very exciting.
00:52:55.520 And then limited time we have left, I want to make sure that we touch on some of the
00:53:00.960 political themes that you raise in your book. I mean, it really is part of the,
00:53:07.280 what I enjoyed about the book was that it was so broad and you had these very powerful ideas,
00:53:12.480 especially about accepting our fallibility as kind of a mode to constant self
00:53:19.440 improvement and applying that in all these different fields, science, culture, and politics.
00:53:26.400 So when it comes to politics, I wanted to ask you whether or not you think that, you know,
00:53:36.080 Francis Fukuyama had this, I had a book called The End of History where he's saying that in a very
00:53:42.240 broad sense, democracy plus free market capitalism represents the best we can do as far as finding
00:53:50.160 a way of organizing ourselves. And I just wonder, although, you know, of course there's a lot
00:53:56.640 of tweaking we can do. I just wonder if you agree with that or if you think that there could also
00:54:02.160 be infinite progress in the realm of politics. The same arguments that I use in the book for
00:54:09.280 everything else apply automatically to politics and imply that that infinite improvement, unlimited
00:54:16.240 improvement is better word, is possible there too. The liberal democracy plus free market capitalism
00:54:24.720 is the best known, the best existing knowledge of this. And so I would guess that Fukuyama,
00:54:33.280 despite recent hiccups in his predictions, is right that the ideas that had been the main
00:54:45.760 rivals to those ideas, during let's say the early 20th century, such as totalitarianism, communism,
00:54:53.120 and so on, that those are going into the dustbin of history. I think that is very different
00:55:01.840 from saying that our best guess as to how to create new political knowledge is going to be
00:55:09.120 just our current institutions. I'm sure that unlimited improvement is possible there too.
00:55:16.880 For one thing, we haven't solved the enormously important problem of how to transmit
00:55:23.840 this knowledge to political cultures that don't yet have it. And it seems that there's something
00:55:30.480 about our existing political culture that is actually antagonistic to transmitting it outside its
00:55:37.760 natural home. So that will be a major improvement because as Martin Reiss said in his recent
00:55:49.760 book in which he predicts that there's only a 50% chance of civilization surviving the next
00:55:56.320 century, progress in other areas, especially technological areas, mean that smaller and smaller
00:56:06.640 numbers of people are going to be able to do larger and larger amounts of damage. And so unless the
00:56:13.520 means of promoting the resolution of agreements without violence can be propagated to basically
00:56:30.720 the whole world, we're going to be an increasing danger from things like weapons of mass destruction
00:56:36.160 in the hands of terrorists. By the way, I think this is not just a political, a problem with
00:56:44.640 improving our political system. It's a general problem to do with technology and everything else
00:56:50.560 because apart from trying to, I should say that that our civilization, the civilization of the
00:56:59.520 west of liberal democracy and capitalism and so on, is within itself, inside itself, it is by far
00:57:07.760 the most peaceful as well as the most rapidly progressing civilization that's ever existed.
00:57:15.120 But I think that apart from having to improve it further in order to allow it to survive,
00:57:20.560 there's another thing we have to do and this is a big theme of my book as well.
00:57:24.400 We have to continue to make rapid progress and it's not just for its own sake, but in this
00:57:31.120 context of, in this political context, it's because rapid progress is the basic means
00:57:40.560 by which the good guys can defend themselves against the bad guys. I've said that technology
00:57:49.840 makes a smaller and smaller number of people able to cause larger and larger effects. Well that
00:57:56.240 has to be offset by the larger number of people, the good guys, making at least as much progress
00:58:05.040 as that in order to be able to cause even larger effects in self-defense. So it's a rapid
00:58:14.560 progress that is our major means of self-defense against the instabilities caused by small numbers
00:58:24.640 of bad people. Okay, I've got to stop you there. That sounds to me like more arms races in the
00:58:33.840 future. We've already been down that path and produced nuclear arsenals capable of destroying
00:58:40.960 all life on earth. Yes, that's not the implication of what I was saying. That's to interpret it
00:58:49.280 in terms of the technology of the past. It's a sort of reductionist interpretation, if I may say so.
00:58:56.640 The kind of, for example, protecting ourselves against nuclear attack during the Cold War
00:59:04.960 was done and rather imperfectly done by developing ways of nuclear attack ourselves. But protecting
00:59:15.520 against, let's say, biological warfare attacks has got nothing to do with, well, perhaps it also
00:59:26.080 involves developing weapons as a means of developing antidotes against them, but it's basically
00:59:32.800 what we need in the case of biological warfare is antidotes, not weapons, and antidotes are,
00:59:40.640 and this is going to be increasingly so as the complexity and knowledge in society becomes the
00:59:49.120 thing that we need to protect. Once we have, for example, once we are able to download our brains
00:59:58.960 into our minds, from our brains into computers and so on, then physical protection of them
1:00:10.880 will become much less important compared with protection of them from bad ideas which would use
1:00:20.400 creativity to destroy all backups. I'm talking about the ultimate extreme of the process,
1:00:31.200 which is already there in the fact that defending against biological weapons involves not
1:00:39.840 biological weapons, but antidotes. That kind of rapid progress is essential to the future of
1:00:46.160 civilization. One other, okay, boy, you're just popping open cans of worms all over the place here,
1:00:55.840 David, and we're basically out of time, but I just wanted to make sure that we touched on,
1:01:02.640 at the very end here, you refuse on our environmental problems on global warming, the question of
1:01:11.440 sustainability, you're quite critical of the concept of sustainability, and also of what you might
1:01:26.640 call, I don't know, environmental alarmism, you recall hearing Paul Erlich give one of his
1:01:32.960 gloom and doom speeches decades ago, and you were pretty dismissive because you thought that
1:01:38.560 Erlich wasn't anticipating any technological progress that might help us overcome these problems.
1:01:45.600 So give us a quick picture of your view on our sustainable or not sustainable future.
1:01:56.160 So I think it's a great pity that the issue of how to manage the environment has become a
1:02:05.680 political issue, because as a political issue, it has become dogmatic, and the dogmas on all
1:02:12.560 sides are simply false. They contradict the arguments of my book that, I mean, what more can I
1:02:21.760 say? On the one side, we have the people who say that the only way of ensuring our survival in
1:02:32.480 the long run is in damping down our impact on the environment. Now damping down our impact on the
1:02:41.120 environment is itself an impact on the environment. There's no fundamental difference between
1:02:48.400 changes that we cause, changes that it causes, or changes that we cause by trying to undo
1:02:54.160 things that we have done. All those things require knowledge, all of them require technology,
1:02:59.840 all of them are going to give rise to unknown problems in the future. And on the other hand,
1:03:06.400 there are people who try to deny that physics is relevant if it contradicts the political dogma.
1:03:17.920 And that's not true either. It's a rather unfortunate that in the case of global warming,
1:03:26.080 the exact details of how soon this is going to become a major problem depend on supercomputer
1:03:34.720 simulations. The thing is that it is going to become a problem eventually doesn't need
1:03:42.240 supercomputer simulations. It's politically important whether the tipping point is likely to
1:03:49.600 come in 50 years or 150 years. The difference between those is enormously important politically,
1:03:57.280 but it's not at all important technologically it seems to me. It seems to me that in both cases,
1:04:03.360 we need a very rapid progress and we need to assume that the solution is going to come from this
1:04:10.880 rapid scientific and technological progress and that this won't be the last problem that
1:04:16.800 ever faces us. What strange arrogance it is among the opponents of arrogance in technology
1:04:25.600 to assume that global warming is going to be the last major problem that will ever face our
1:04:31.200 species. That seems to me ridiculous and the task of technology is not to optimize the entire planet
1:04:44.480 to solve one particular problem that we happen to know about, but to give us the means of
1:04:51.360 first of all addressing problems that we do not yet know about and secondly,
1:04:57.440 the means to recover from disasters that will also inevitably happen when we make mistakes.
1:05:05.040 And both those things dealing with unforeseen problems and recovering,
1:05:10.720 both those things require knowledge and that's why we need to increase knowledge as far
1:05:18.240 as we can. One final question and I'm sorry about your answer has to be fairly brief.
1:05:27.040 I just wonder where your optimism comes from. I hope you don't mind my saying. I don't mean
1:05:33.840 this as an insult, but it approaches a kind of faith and I wonder if that faith has anything to
1:05:43.840 do with a kind of spirituality on your part, a belief and I don't know God or something.
1:05:51.760 So, well first of all, I deny it. I deny that I have any faith, religious or otherwise,
1:05:58.720 and I deny that I have any spirituality and I also deny that this optimism is an attribute of me.
1:06:06.960 It's as if you were saying what kind of predisposition to multiplicity led you to become
1:06:16.800 a defender of the parallel universes interpretation. That's not how it happened. The reach
1:06:22.400 comes from the ideas, not from what I want them to say. So, I can no more deny the links between
1:06:33.200 the theory of evolution in biology and in, let's say, human ideas than I can deny that they
1:06:41.040 apply to one particular animal. If the theory of evolution is true, then all animals evolved
1:06:48.320 and if somebody wants to say all animals accept elephants or as historically happened,
1:06:54.240 all animals accept humans evolved, then that doesn't make sense as an explanation and what
1:07:01.200 I'm about, what my books are both about, is taking explanation seriously and requiring them to be
1:07:08.400 good explanations, not requiring them to meet predetermined implications. Listen, there are a lot
1:07:20.720 of pessimists out there. As you know, I'm sure you've gotten some pushback against your vision
1:07:28.960 of the future. So, I urge them all to read your book and give your ideas a chance and it might
1:07:36.960 even make some of those pessimists out there a little less gloomy. Well, that's great and I'm
1:07:42.080 glad that you're not one. I'm working on it. Thank you very much, David. It was really a pleasure.
1:07:48.640 Okay. Nice talking to you. All right, same here.
