00:00:00.000 Welcome to Topcast and to the long-awaited or at least often mentioned episode 100.
00:00:27.040 This here is finally my interview with David in full, unabridged form.
00:00:31.960 It contains all my questions for David and multiple more questions.
00:00:39.760 My friend recently told me that he doesn't like it when I say to audio-only listeners
00:00:43.960 that the YouTube version is sometimes better because I put lots of pretty visuals in it.
00:00:48.440 He says that he listens while he's out walking or jogging and can't look at a screen.
00:00:52.520 Well, today Adam, you don't need to worry about that.
00:00:55.680 And to all the other atoms out there who I think outnumber the YouTube viewers by about
00:00:59.920 a 10 to 1 ratio, I'll keep in mind moving forward as we say, that so many of you only
00:01:06.560 listen and don't watch screens, perhaps it would be more fair if it was a 10 to 1 ratio
00:01:12.680 of audio-only to visually important podcasts from now on, we'll see.
00:01:17.600 So this episode is, I have to say up front, rather an astonishing personal accomplishment
00:01:26.720 Among my peer group, like any group of school kids, I guess, the common thing was looking
00:01:31.440 up to famous sports stars or music idols or movie stars.
00:01:38.000 This was back in his early days of doing movies, not his more recent political stuff.
00:01:42.160 Back then, he was quite the optimist and his personal story was easily as heroic as any
00:01:52.200 I'd ever get to meet Arnold much less, have a conversation with him.
00:01:56.200 I lived in Australia in the southwestern suburbs of Sydney.
00:01:59.200 It's not the place to come across movie stars, sports celebrities, singers or accomplished
00:02:06.040 But happily for me, some intellectual heroes of mine were accessible by pure chance and
00:02:13.720 I've mentioned before on this podcast that Professor Paul Davies, author of The Mind
00:02:17.960 of God and many other books, produced a couple of physics documentary series here in Australia
00:02:25.720 He also used to write articles for local news outlets and he appeared on TV here rather
00:02:29.880 regularly when he did live here in Australia for a time.
00:02:33.360 I read, listen to and watched anything and everything Professor Davies ever put out there
00:02:39.560 And early on, he was the guy, my scientific hero, so to speak.
00:02:48.160 When one day, he just happened to turn up and announced at an event I was helping to host
00:02:55.240 I actually got his autograph on my philosophy uni notes as it turned out.
00:03:00.640 The name of the subject in which the uni notes were compiled was called God Life the
00:03:05.160 Universe and Everything, which was right up his alley.
00:03:07.960 And the lecture notes actually had excerpts from one of his books that I proudly showed
00:03:12.760 I was literally studying his stuff at the time.
00:03:14.600 So I ended up having a brief conversation with Paul Davies, winner of the Templeton Prize.
00:03:18.840 And I kind of thought that in my early 20s, this was a pretty good accomplishment for
00:03:22.360 an undergrad physics student still living with their parents in an exceedingly typical
00:03:26.600 home on a typical street and a typical suburb, one among hundreds in greater Sydney Australia.
00:03:32.120 I guess to put it in perspective, it would have been rather like an aspiring pop singer
00:03:37.560 just happening to bump into Michael Jackson or Madonna or for younger listeners Justin Bieber.
00:03:43.320 So that was the late 90s by which time I'd already read the fabric of reality by David
00:03:50.200 And the remarkable thing about having read that book was that I just had to talk about
00:03:56.000 I think many people who read the book end up feeling that way.
00:04:02.720 As much as I loved Paul Davies books, I never really felt a need to discuss them with
00:04:10.080 But sadly, there was no one to really talk to about it at university.
00:04:13.680 The people around me, even in my physics lectures, just didn't seem to get the significance
00:04:19.320 Well, of course, they hadn't read it to begin with.
00:04:21.160 At the same time, I was reformulating my own thoughts from decades of schooling and some
00:04:26.440 years of tertiary education in light of what the fabric of reality was saying about
00:04:33.320 I was converted by that book to the many world interpretation of content theory.
00:04:41.800 In other words, I had some insight into what knowledge actually was and how it was created.
00:04:47.160 But whenever I mentioned either of those things, let's say many worlds to a physics
00:04:51.680 tutor or professor, or Poppa to a philosophy tutor or professor, I barely ever got more
00:04:57.480 than a shrug or maybe a hint that I should go and read about bomian mechanics or maybe
00:05:02.240 take more seriously what Feynman had to say about understanding content theory or in the
00:05:07.200 case of Poppa to look more deeply into the Vienna circle and what Wittgenstein had to
00:05:12.280 say on the matters that Poppa was writing about.
00:05:14.800 In other words, in both cases, there were not many sympathetic ears.
00:05:18.840 Now I cannot remember exactly how it happened, and this is in the era before Google.
00:05:23.760 But some search engine or other allowed me to eventually find myself online in the late
00:05:28.760 90s and the early 2000s, able to now and again, fire a question to David Deutsch himself
00:05:38.000 I was astonished that he was the guy, the inventor of quantum computation, that seemingly
00:05:42.960 no one much knew about, but seemed to know a heck of a lot more and make considerably
00:05:47.960 more sense than anyone else I'd ever encountered in academia or intellectual circles.
00:05:54.440 I was one of the privileged few in retrospect who knew a second book was on the way,
00:06:00.600 so we never knew what it would be called, nor when it would arrive, but the anticipation
00:06:05.120 grew over the decade until finally it was published.
00:06:08.680 I think perhaps only Star Wars fans, waiting for the next canonical film to drop, no exactly
00:06:17.600 Films are a transient thing, but a book, like the beginning of an infinity, is kind
00:06:22.120 of bottomless in a way that no other consumable content quite is.
00:06:26.720 So I've been a fan of David Deutsch for decades now.
00:06:30.120 So it still blows my mind that I could be in a position to actually just have a chat
00:06:34.560 with him as we do here, albeit from the other side of the world.
00:06:38.880 And on that, me being far closer to Antarctica than most of the population of the planet,
00:06:44.760 and most people who are listening to this will be far closer to the Arctic, the finiteness
00:06:48.800 of the speed of light did catch David and I out on more than one occasion, making this
00:06:54.080 episode in some places a little bit disjointed, so editing was required for listenability
00:07:00.080 in some places, but hopefully I've done a good enough job that you don't notice.
00:07:06.200 This seemed to be half-conversation, half-interview, and I have learned now on putting this
00:07:11.600 together to not speak over the person I'm talking to, or try to fill pauses with noises
00:07:17.800 I have learned those lessons now, but I did not know them beforehand, which means there
00:07:22.320 are some places where I do seem to forget, I am being recorded.
00:07:27.080 As this episode 100, a sort of announcement is in order, that being that top cast will
00:07:32.320 continue to go from strength to strength in a space of podcasts that seems to expand continuously,
00:07:38.280 but I think there is a nice little niche here that needs to be filled, so I'll continue
00:07:42.040 doing what I do, but with more energy thanks to the support of Patreons, and especially
00:07:47.440 of course to Naval Ravikant, whose own worldview and wisdom aligns so closely with the
00:07:53.200 optimism, view of progress, and wealth of David Deutsch, and what I am trying to promote
00:07:59.520 So I'll continue doing what I do, which is long-form podcasts, especially on Deutsch's
00:08:04.720 the fabric of reality, Marletos, the science of canon Kant, and Pinker's rationality for
00:08:10.840 But I'll also be broadening out and refining things, making lots more standalone episodes
00:08:16.040 and really tightening things up on some of the ideas we like to talk about here, and
00:08:25.400 And maybe now and again I'll do the odd recorded conversation once in a while.
00:08:29.160 So look forward to that in the coming weeks, and months, and the years, if you're a fan.
00:08:34.600 This introduction is already longer than I hoped for, but I actually haven't done a job
00:08:38.840 of introduction, which I should do in an episode like this, I need to introduce my guest.
00:08:44.120 Of course, David needs no introduction, especially if you're listening to this as a subscriber
00:08:48.560 of Topcast, because Topcast is largely a podcast devoted to the work and worldview of David
00:08:57.080 Deutsch, the inventor of the theory of quantum computation, author of the first quantum algorithm,
00:09:02.920 intellectual successor to the epistemology and philosophy of Karl Popper, author of the fabric
00:09:07.720 of reality and the beginning of infinity, creator of Constructa Theory, David is a fellow
00:09:12.880 of the Royal Society winner of the Dirac Prize in 1998 for quote, pioneering work in quantum
00:09:19.480 computation leading to the concept of a quantum computer and for contributing to the understanding
00:09:25.440 of how such devices might be constructed from quantum gates in quantum networks.
00:09:30.840 And he was also the co-winner of the Dirac Medal in 2017 for quote, building the foundations
00:09:39.920 His books have won prizes and he is one other prizes as well, go to his website and the
00:09:44.840 about me section to find out more about all that.
00:09:47.920 But as I record this, I've just learned that this week, the final week of November 2021,
00:09:52.960 David has won the Isaac Newton Medal from the Institute of Physics in the United Kingdom
00:09:57.720 for quote, founding the discipline, named quantum computation and establishing quantum
00:10:04.400 computations fundamental idea now known as the qubit or quantum bit end quote.
00:10:10.240 He has now also been elected a fellow of that Institute of Physics, prizes, accolades
00:10:15.440 and accomplishments aside the impact of David Deutsch on the world is yet to be fully realized
00:10:21.680 but it is going to become perhaps something like that of an Einstein or a Newton or a Darwin
00:10:27.840 in my opinion, which is why we're so lucky to be able to interrogate him once in a while.
00:10:33.520 Once the first fully functional universal quantum computer is built, the landscape of the
00:10:39.240 When the average person understands and appreciates that its function can only be explained
00:10:43.440 by recourse to a multiverse, the intellectual world will change.
00:10:47.480 When people look back in retrospect and realize he was right all along in what he said
00:10:51.760 about quantum computation and therefore about explanations and hence Papa, the world will
00:10:58.680 We can only hope that that change goes deeper still into how the education of young people
00:11:03.720 is handled, how we deal with problems both known and unknown and why progress, optimism
00:11:09.120 and wealth need to motivate us all individually and as a civilization.
00:11:14.000 The world will be changed and we will see that what I've just said about putting David
00:11:18.320 alongside the biggest names in science and philosophy is neither hyperbole or hubris.
00:11:30.080 I'll have a few brief remarks at the end of this, but for now I present to you my
00:11:35.360 interview, my discussion, my conversation with David Deutsch.
00:11:40.080 Okay, well thanks very much anyway for doing this David.
00:11:46.200 It's a real honour to talk to you and be able to record this conversation.
00:11:52.040 In this book that I've spent the last few years exploring now is unlike just about any
00:11:59.120 other to my mind and I've said this a few times that it's unlike other popular science
00:12:03.680 books because it's not really a popular science book.
00:12:06.960 One thing that it contains within it that is different to other science books is what
00:12:11.560 I might say are sort of discoveries in philosophy and physics or at the very least new ways
00:12:17.160 of refining and explaining material you've put out there elsewhere in other forms perhaps.
00:12:22.640 The first time this seems to crop up actually is in chapter one, the reach of explanations
00:12:27.240 and there we get the concept of good explanations, good explanations being, actual explanations
00:12:32.520 that account for what it's out there in the world and how it works, that are hard to vary.
00:12:39.280 Now I'm convinced and most people who hear about it become convinced over time, but I think
00:12:45.280 there's a lot of people who think, well science isn't it just about testable theories,
00:12:51.960 So there was a lot about explanations even in my first book and some careful readers pointed
00:13:00.680 out that I'd never actually explained what an explanation is in the fabric of reality.
00:13:08.240 In fact, I seem to have taken a bit of a cop out pass by saying just saying about explanations
00:13:15.120 that there isn't any closed list of attributes that an explanation must have and that's
00:13:21.760 because it seemed to me that, and I think it does seem to many people that the difference
00:13:27.920 between an explanation and a prediction is obvious, but to most people it was quite opaque.
00:13:39.160 So I thought about it and this is indeed one of the few things that I will acknowledge
00:13:44.520 is kind of a bit of an innovation in the beginning of infinity, I thought about what exactly
00:13:53.560 makes the difference and I thought of some examples such as the explanation of the seasons
00:14:01.640 as opposed to predicting them and then I think that the example that I like best, although
00:14:07.440 again, not everyone does, is the example of the conjurer where you go in and you go in
00:14:17.200 to see this conjuring performance and you see some cups and balls and the conjurer puts
00:14:24.160 the ball under the cup and after a while you begin to predict that the cup way he puts
00:14:31.160 the ball under is not going to be the one where it ends up.
00:14:34.880 But that doesn't mean you can explain what's going on in the trick.
00:14:40.040 So you can predict quite confidently that the ball isn't there and there you are, it's
00:14:47.200 But that's not what you mean by how is the trick done.
00:14:52.480 What you mean is what has happened to bring about the thing you saw.
00:14:58.240 So you're not asking for an account of the thing you saw, even a perfect prediction of
00:15:04.520 the thing you saw, you're asking about the thing you didn't see.
00:15:10.560 And this comes up so often throughout the book really and I think it's a subtle point
00:15:17.360 And of course the other example that you use and that you often go to is this idea of
00:15:23.080 The one thing that you actually can't observe is indeed the one thing that you're invoking
00:15:28.400 as actually existing and causing the phenomena that you do observe.
00:15:31.960 And I think in all these cases that unobserved thing is the thing that you're really interested
00:15:38.720 It's the only reason you're interested in any kind of prediction at all.
00:15:43.120 And now this concept of then hard to vary where all the parts of the explanation have
00:15:49.240 some functional role and this is really what makes the explanation a good explanation as opposed
00:15:55.360 to any arbitrary account that could be easily varied, mythological accounts and so on, magical
00:16:03.800 Did you have that in mind during the fabric of reality, writing it then, or did it only
00:16:08.000 come later in light of people saying, you know, can you sharpen up what you mean by explanation?
00:16:14.360 Like I said, while I was writing the fabric of reality, I kind of thought that these were
00:16:22.360 I thought that these were words that had an uncontroversial meaning.
00:16:27.240 And it didn't occur to me that most people would not have this meaning in mind, although
00:16:37.760 So in that sense, it wasn't something I invented or something that I realized needs to
00:16:50.440 And then I started to think about, well, things that are explanations and things that
00:16:53.680 aren't explanations and like the ancient myths and so on.
00:16:59.040 And then I thought with the conjurer, there are circumstances where the conjurer did it
00:17:10.720 Can you imagine a person who believes in magic and is slowly coming out of that state of
00:17:18.840 mind, like James Randy's family, the historian when he was a teenager and when he first
00:17:27.840 exposed a fake psychic and was horrified to find that most of the people in the audience
00:17:40.320 There was a famous, I don't know if you know the famous story that he was on Australian
00:17:44.280 It was the same to the spoonbender, Yuri Geller, on one of our daytime lunchtime talkback
00:17:51.360 And the audience was very upset with him and indeed the host was as well and stormed
00:18:01.160 I mean, that anger would happen, I suppose, whether or not he revealed how he did it.
00:18:09.600 It was the fact that he was revealing that he did do it, that was the thing that angered
00:18:16.400 And that was the relevant explanation in context.
00:18:19.840 So that's why I have to say, it's an explanation is hard to vary, while still solving the
00:18:26.760 problem that it purports to solve, which might be different for different people as well
00:18:34.760 I think that piece of sort of prozac terminology explanation that we all use, but I think
00:18:40.840 that you've put a spin on it that is quite helpful.
00:18:44.000 But turning to another word, a word that you in fact don't use, and it brings me to
00:18:48.720 chapter two, and that's called, don't worry, I'm not going to go through every single
00:18:52.320 chapter chronologically, but then just a few of them, but chapter two is titled closer
00:18:58.920 But car popper had this term vericilmatude, which means something like closer to truth.
00:19:05.000 And it seems to me you've deliberately avoided that word, but why is it because it contains
00:19:10.240 a misconception, it's misleading, or it's a needless neologism, what would be the reason
00:19:15.840 I think all of those things, and I think even pop, I don't know the history of this
00:19:20.280 very well, but I think even pop or went off it, pop in general was very into logic.
00:19:28.000 This is, I think, partly a sign of the times that the people who were doing the prevailing
00:19:36.240 philosophy of science at the time, and positivism, and logical positivism, many of them were
00:19:44.840 Pop or wanted a, pop or originally didn't want to mention truth at all, and then he got
00:19:52.880 converted by Tarski, and he tells a story about how they were sitting on a park bench
00:19:58.800 in Vienna, and Tarski explained the correspondence theory of truth to him, and he realized
00:20:03.720 that this is, in fact, a useful concept after all.
00:20:08.880 But I wonder what logic or scientific discovery would have looked like if he had, in fact,
00:20:14.160 written the whole of it without ever mentioning truth.
00:20:16.880 I think it would have been worse in some ways in that it's difficult to make
00:20:22.800 the case for realism if you don't have a concept of truth, and pop or was very keen to
00:20:32.560 But on the other hand, when you do introduce truth and especially very similitude, then
00:20:38.280 the idea is that somehow we can utter truth, or at least we can utter something that's
00:20:46.400 And we'd have a thereby a method of measuring that 90%.
00:20:49.360 And I think very similitude was not intended to be something you could measure, but if you
00:20:55.360 can't measure it, then its only use is a sort of philosophical regulating principle.
00:21:03.200 And I think knowledge and problems are much better concepts.
00:21:10.160 Probably Papa's fundamental concept, the way it turned out when after all these experiments
00:21:18.280 were different conceptual frameworks or whatever, is the idea of a problem, because that
00:21:23.800 comes up not only in his philosophy of science, but in his political philosophy as well,
00:21:29.800 and more generally, he generalizes it to even the problem situation of a gene.
00:21:41.280 I'm not sure even I would go that far, but it's a very unifying concept.
00:21:47.520 And on the other hand, I don't think very similitude is useful at all.
00:21:52.200 And as I said, even truth one has to be very careful to use the concept of truth only
00:22:00.440 as a property of abstractions, and never as something you can actually measure or know
00:22:13.560 But therefore, would you avoid even saying that scientific explanations, indeed explanations
00:22:19.720 in any domain that would happen to be interested in, would even be approximately true,
00:22:24.440 because that would also entail some kind of quantitative claim about how close we are.
00:22:33.200 Or it's a, there's some degree of accuracy in this claim about that, I think we can
00:22:39.360 use it because, again, depending on the problem situation, if one is speaking informally,
00:22:50.040 I just caught myself just a moment ago saying probably, so I'm generally opposed to the
00:22:58.160 I think it's a scam, but that doesn't mean that in everyday life we don't know what
00:23:05.240 we mean when we're saying, you probably meant so and so, I don't mean that there was
00:23:12.440 a stochastic process where he could have meant something else with the probability
00:23:19.320 Yeah, I often find myself catching myself precisely the same way that you said.
00:23:25.480 Generally, it kind of has left my vocabulary in just in day to day life using the word
00:23:31.000 probably, but at the same time, I don't, you know, chastise myself too much because in
00:23:37.200 order to communicate normally, you know, people are going to use this word and I understand
00:23:40.840 I think there isn't as such things as a perfectly precise language, so we want to use terms
00:23:50.560 and ways of understanding things that are suitable to the problem.
00:23:58.880 Making people, for example, as chemical scum might be, a very loose way of understanding
00:24:03.480 what people are, but Hawking did it and you have an excellent refutation of this claim
00:24:09.760 that Stephen Hawking did make, which seems to be the reasonably scientific way of understanding
00:24:17.880 He said that we are just a chemical scum on the surface of a typical planet orbiting
00:24:24.440 But you say this place is not typical, is it, in what sense is it not typical?
00:24:29.280 I think the description of humans as a chemical scum on earth is not accurate in the
00:24:37.720 problem situation in which Hawking used that term.
00:24:42.320 We are certainly made of chemicals, but so is the rest of the earth and so is all other,
00:24:54.120 So to single us out as a scum in these, if you are going to take these terms in the context
00:25:05.240 of trying to describe something purely in terms in reductionist terms of their constituents,
00:25:11.680 then it is simply false to add a pejorative term.
00:25:17.320 That pejorative term comes from a different problem situation and a different vocabulary is
00:25:25.320 It would be enough to say we are chemicals like everything else in the universe and then
00:25:32.160 you see that it would be silly to call the earth a chemical scum or the sun or the solar
00:25:36.880 system or the Milky Way galaxy as a chemical scum, though in the sense in which we are,
00:25:44.960 So we are a special, a very special kind of chemical, but then would that entail that
00:25:52.480 the earth is special by virtue of the fact that it is uniquely suited to ensuring that this
00:25:59.760 set of chemicals called us is able to survive off into some future, that we are only sustained
00:26:07.920 by the existence of this planet and will only continue to be sustained by this planet.
00:26:12.400 So therefore we better look after the environment or else we are going to go extinct.
00:26:16.640 Yes, so you are putting that in a deliberately exaggerated way that makes it much more
00:26:24.920 You could have said that with one tenth the emphasis and it would still be wrong.
00:26:32.000 Now it is true that the earth is that living things can exist on earth, only by virtue
00:26:37.640 of the fact that the earth provides astronomical standards a very unusual set of circumstances,
00:26:46.800 which if they were to vary by astronomical standards by only a few percent, then without
00:26:54.320 a lot of technology we would die and living things in general would die without technological
00:27:00.880 help, but that does not at all mean that the earth is adapted to human existence or even
00:27:09.800 to life, but especially to human existence very accurately.
00:27:16.440 It is more true to say that the earth is barely suitable for life.
00:27:23.480 It provides a relatively stable temperature and sunlight and living things manage to use
00:27:34.800 that even though it is not very conveniently provided and that took it hundreds of millions
00:27:41.680 of years to work out and the rest was provided by life itself and most of the rest as far
00:27:55.560 There are very very few places on earth that humans can live comfortably without technology
00:28:05.440 that is without ideas provided by them and not provided by the earth.
00:28:12.400 So I don't know maybe some South Sea islands with suitable coconuts or whatever they have
00:28:20.280 But even that would be a trap because we are so constituted that if we did live in such an
00:28:27.840 environment for some generations our numbers would increase to the point where we were living
00:28:38.360 So the earth is living on earth what has been provided is really just the bare necessities
00:28:47.080 for us to live somewhere originally the great lived rift valley or something and the rest
00:28:54.920 Yes so the earth is not adapted to life but life can adapt itself to the earth but the
00:29:02.160 only thing that is going to survive in the long run in terms of regular life, not intelligent
00:29:08.960 life like ourselves, the genes the genes are going to want to try and make themselves survive
00:29:13.360 and the animals won't care or the other species don't have this concept of caring into
00:29:19.640 the infinite future about their own survival however we do so we want to adapt ourselves
00:29:26.640 to the earth in some way or if not the earth in something far larger we want to adapt
00:29:33.360 ourselves to the universe in which we find ourselves.
00:29:36.720 And the one thing that enables us to do that is of course solving our problems continually
00:29:41.920 to create the knowledge in order to enable us to do so.
00:29:45.400 And you have the great dichotomy of saying problems are inevitable but problems are soluble
00:29:52.000 and here I have heard over the years people push back against this especially the second
00:30:00.400 For example they argue we can't know everything and they will invoke that it's provably
00:30:06.960 the case that given girdles result there are true statements we cannot prove are true.
00:30:12.440 So there is some and there are some mathematics it's not decidable so some problems are
00:30:16.560 not soluble isn't that correct what's the argument against that line of reasoning.
00:30:22.840 I think that this line of reasoning is reaching for a standard of knowing that it's impossible
00:30:33.800 for anything it's not possible to know even provable things by the standard that they're
00:30:43.160 When we say that something is provable we mean that it's provable from certain axioms
00:30:49.760 and girdles theorem is about provability which means provability from axioms.
00:30:56.240 Now if you have an undecidable statement in some formal system and if it was true you
00:31:03.200 could always add that as another axiom and then it would be provable.
00:31:08.480 So you might ask yeah but how do we know that that statement you're adding is true if
00:31:15.920 Well unfortunately that objection applies to any set of axioms and it applies to the original
00:31:22.960 set of axioms as well and this is a mistake that has been made by many mathematicians
00:31:31.120 even after girdle I think it was made by virtually all mathematicians before girdle but
00:31:38.520 even after mathematicians tend to think that there is a class of axioms that don't
00:31:46.240 need proof or something that they are self-proving or self-evident or they come from
00:31:53.480 mathematical intuition which is infallible or something like that.
00:31:57.920 But in fact the axioms, the rules of inference in logic that for example if the proposition
00:32:05.440 A and B is true then it is necessarily the case that B is also true.
00:32:12.440 Now it seems self-evident but it is not provable so what are you going to do?
00:32:20.200 Are you going to say that this is a problem that is insoluble and therefore it's not true
00:32:27.960 No people don't bother saying it with axioms because they have this misconception that
00:32:34.100 axioms are somehow enshrined by God or something and we can know for sure that they
00:32:44.080 We are trying to solve problems, we are not trying to establish truths and girdles,
00:32:50.600 but the theorem is not about establishing truths either, it's about deriving things from other
00:32:57.480 Yes and there is some one line of discussion I often pursue here and correct me if I'm
00:33:04.560 wrong but this vast class of undecidable, unprovable statements which must vastly outnumber
00:33:16.200 They're in a sense uninteresting because that's not what the claims of science, physics
00:33:23.960 for example consist of and so they don't have and again I would appeal to your better
00:33:29.920 knowledge on this, they don't have any, they can't possibly have any effects on our world,
00:33:37.320 they're not going to help us to solve problems as we would say.
00:33:40.960 We know they exist but beyond that what are they interesting in any way?
00:33:46.160 Well they're certainly interesting because mathematics is interesting and we're interested
00:33:51.160 in abstractions as well as in physical problems.
00:33:56.480 The reason that it seems implausible at the moment that undecidable propositions might
00:34:04.960 be relevant to some practical problem like how to feed the world or how to eliminate
00:34:11.680 viruses and so on is that the undecidable propositions are all about infinite sets, infinite
00:34:19.880 sets of things like the set of all numbers and that kind of thing and physics as we currently
00:34:28.640 conceive of it, the infinite sets that appear in physics are very tame and don't have
00:34:37.400 But that's like I can conceive that maybe one day somebody invents a different physical
00:34:42.880 theory where the undecidability of certain propositions about the real numbers would tell you
00:34:51.320 something about how to do and how not to do certain things that you want.
00:34:59.080 I think Roger Penrose once pointed out that certain theories of quantum gravity do depend
00:35:09.200 Basically it's like if you're working out a Feynman diagram to work out what the probability
00:35:17.440 is that a certain gravitational wave will interact with another gravitational wave.
00:35:25.600 Then if you want to work that out accurately you have to do a sum, you have to sum the
00:35:30.080 amplitudes for all possible processes over all geometries and for all possible topologies
00:35:39.440 and to enumerate all possible topologies in the relevant sense, I'm not a mathematician.
00:35:45.880 I don't know about this stuff but apparently that's an undecidable task and therefore
00:35:51.920 you couldn't work out this probability amplitude for the gravitational wave doing something
00:35:57.760 rather because you would have to have a mathematical expression for all topologies in a given
00:36:06.440 So that's an example of how in principle laws of physics might have undecidable consequences.
00:36:13.440 Yes and therefore that the under-siderable consequences are actually interesting.
00:36:21.320 Yes, in principle, something that you wanted to do might depend on working out this thing.
00:36:29.480 But I don't see any particular reason for making a distance, as long as we have the
00:36:35.840 necessities of life and comfort, I don't see any reason for making a distinction between
00:36:42.160 problems in engineering and in physics and in pure mathematics, they're all problems,
00:36:49.640 they're all conflicts between theories that interest people, people want to know what
00:36:55.800 One thing I say in the book about pure mathematical problems is that sometimes discovering
00:37:03.760 that something is undecidable is the solution to the problem in the sense that it's the
00:37:10.280 problem, it's what you wanted to know because you have in mind some prima facie argument that
00:37:19.960 is true and another prima facie argument that it's false and then you discover that it's
00:37:27.040 actually undecidable and that explains why you could have these two conflicting intuitions
00:37:34.640 about it and then you can go and criticize your intuitions in other ways because
00:37:40.240 you know that you're not going to be able to resolve it by proving one of them true or false.
00:37:46.520 Now you mentioned in that answer the concept of abstractions and you actually invoked abstractions
00:37:52.000 in talking about it of course pure mathematics is about abstractions and I don't know what
00:37:57.040 might be the most controversial chapter in the book but I think among intellectual types
00:38:01.320 to at least some extent it would be chapter five if it's not going to be the white flowers
00:38:06.920 a beautiful chapter it's going to be the one that claims there is a reality to abstractions
00:38:13.600 because to some people this seems weirdly enough you know not to me I think not to most
00:38:18.840 people listening to this but it can sound like an appeal to the supernatural or some sort
00:38:24.160 of woo because some people are physicalists they think that everything just has to come
00:38:30.080 down to the behavior of atoms but I wanted to ask you if you distinguish between kinds
00:38:36.080 of abstractions rather than defending the thesis that abstractions are real I know this
00:38:40.800 is not necessarily a world to find area but for example something like numbers their abstractions
00:38:46.240 are they different in kind to let's say knowledge because after all there may be infinitely
00:38:52.920 well there are infinitely many prime numbers and not all of those prime numbers ever
00:38:57.000 need to be instantiated in a physical substrate anywhere nevertheless they still exist
00:39:01.880 but knowledge to be knowledge has to be extensive and stands here in a physical substrate
00:39:07.480 it's also abstract but well I might pull the brakes there can you explain if there
00:39:13.520 are these different species of abstractions and if so how do we understand the differences
00:39:20.440 in their existence yes there are different species of abstractions I mean maybe it's
00:39:27.400 better to say there there is a classification of abstractions and some classifications
00:39:33.480 are quite useful because abstractions within the same category of classification have
00:39:40.440 similar properties and can be understood with similar explanations or the same explanation
00:39:45.720 but then with the different problem situations you might want to classify things differently
00:39:50.880 like you know just like in biology we may wish to sometimes we want to classify things
00:39:56.400 as mammals and birds and reptiles and so on and on other occasions we may want to classify
00:40:03.400 them as aquatic creatures and terrestrial creatures and aerial creatures and so on so
00:40:10.040 classifications are useful relative to the problems that they are that you want to talk
00:40:16.440 about and it's the same with abstractions it's it's definitely true that some abstractions
00:40:22.280 as you say like knowledge and information more generally don't exist unless they're instantiated
00:40:30.040 so they have to have this extra element of being instantiated but that's also true of
00:40:36.360 there are more classifications than that even even among pure abstractions that there
00:40:42.000 are abstractions that it seems to be important in mathematics to like I said to distinguish
00:40:49.920 between abstractions that involve infinite sets and abstractions that don't and then
00:40:56.720 the whole idea of a set is not universally applicable so the set of all sets it famously
00:41:03.600 turned out even before girdle it turned out that this from Russell that it turned out
00:41:09.320 that the set of all sets isn't a set so then you have to invoke a class it's just a
00:41:16.640 class of thing or the set of all sets that don't contain itself so there's there's not
00:41:20.880 that's right so there's but it doesn't help because there's it doesn't help with everything
00:41:26.160 because there's no such thing as the class of all classes either right so yes there are
00:41:33.040 different kinds of things and another thing which which I think is still slightly mysterious
00:41:38.120 is what kind of an abstraction the laws of physics are some people think precisely by
00:41:43.840 arguments such as such as you've mentioned that there really are no laws of physics all
00:41:49.760 there are physical events and physical processes and laws are just a kind way of summarizing
00:41:57.120 physical events and processes they just are so because I see that that looking out of the
00:42:03.600 window I can see that the sky is cloudless at the moment that is some kind of emergent consequence
00:42:10.160 of the laws of physics but it if it's true then people who deny that there are laws of physics
00:42:19.360 will say well that's just a fact about the universe and you could you could summarize it and say
00:42:24.800 that on three of the days of this week the sky was clear and that's not a law of nature so why
00:42:31.760 should we why should there be anything special about the statement that nothing can exceed
00:42:39.600 the speed of light well it's because the statement that nothing exceeds the speed of light is
00:42:46.320 not just a prediction it is an explanation it's an explanation of how the universe is that the
00:42:52.960 universe is a four-dimensional pseudo-remanion manifold with a metric and so on and so on and the
00:43:02.720 fact that the speed of light is finite emerges from that explanation and you could write down
00:43:12.880 all the predictions that follow from that in a sort of infinitely long list of things like
00:43:20.080 like this dog can't run faster than light and this car can't travel faster than light and what
00:43:25.440 once you've made that infinitely long list or maybe just very long very very long list you would
00:43:31.760 have written down everything that can be deduced about what happens in nature but you wouldn't have
00:43:39.200 ever listed that law and you wouldn't have ever mentioned manifolds and four-dimensional or
00:43:48.160 anything like that well you'd have some significant explaining to do wouldn't you it well if you
00:43:54.000 wanted explanations you'd have a lot of explaining to you would in fact have all the explaining to do
00:43:59.680 at the end of that huge process that you had at the beginning you wouldn't have explained anything
00:44:05.200 we were we were just talking about how the nature of physical laws and whether or not and to what
00:44:13.680 extent they might be pure abstractions or a kind of abstraction of some kind and I was just thinking
00:44:19.440 into myself that for anyone who denies the existence of physical laws in their own right laws or
00:44:26.400 physics and to just say well there are just facts of matter about the universe for example
00:44:33.360 the orbits of planets going around stars are approximately circular or elliptical then those facts
00:44:40.960 of the matter those regularities in nature seem to be crying out for an explanation so to deny
00:44:47.200 that there would be really existing physical laws behind those regularities in nature seems to
00:44:52.240 me to be going to a lot of work to avoid what might otherwise be called Occam's Razor well isn't
00:44:58.240 the simple explanation there are physical laws out there governing these things yes of course if
00:45:04.080 somebody insists on the non-existence of explanations like exactly like insistence on the non-existence
00:45:13.280 of anything you can't be proved wrong but I think the motivation for denying the existence of
00:45:23.920 laws is the old mistake of empiricism it is the assumption that raw facts or raw sensory
00:45:36.480 impressions have a privileged status in that we can access them directly and this is this
00:45:45.040 people contrast this with things like laws and explanations in general which they say we can't access
00:45:52.080 directly so they are they have some kind of a lesser reality and we can in principle not insist
00:46:00.640 on there being real one can insist on there not being real and it doesn't make any difference
00:46:05.520 the trouble with that is that exactly the same is true of sense impressions as well
00:46:11.120 and so this argument that abstractions don't really exist or that laws don't really exist
00:46:18.400 and so on hidden in there is the assumption that sense impressions or that kind of thing
00:46:25.520 do really exist in some sense of really which is itself a mistake that all knowledge is
00:46:32.880 conjectural all observations are theory laden there is nothing that is an authoritative source
00:46:40.320 of knowledge everything is conjecture and so what once you've realized that everything is
00:46:45.040 conjecture but that knowledge can still exist then the reason for making a distinction between
00:46:50.720 different kinds of existence well no there is a distinction between different kinds of
00:46:55.920 existence but the justification the motivation for denying that certain things exist even if we
00:47:03.600 need them in our explanations goes away hmm and this once one it becomes at least somewhat familiar
00:47:12.560 with the worldview that you've presented in your books and with Popper's worldview it's very
00:47:18.400 difficult to try and reimagine what people mean by directly observe I struggle now to try and
00:47:26.720 conceive of what one really means when they say well there are certain things you can just observe
00:47:32.080 you can just see but on explaining to them well let's think about what that whole process
00:47:38.080 of seeing actually consists of or photons you know being absorbed and then reemitted
00:47:44.320 back towards the eye and then being converted into electrical signals which then go into your brain
00:47:48.960 this this whole concept of direct observation actually itself vanishes into a cloud of explanation
00:47:57.200 not so much a cloud but a kind of way of understanding the world that denies the possibility
00:48:04.000 of direct observation I don't even know what someone really intends by this terminology this way
00:48:10.480 of denying the reality of things which we don't have direct access to when we don't have direct
00:48:18.320 access to anything even I would tentatively argue that the even the contents of our own minds
00:48:25.120 I agree in a way the contents of our minds are quite a highly sophisticated kind of knowledge
00:48:32.560 that we only know through an extensive chain of interpretations some of which are notoriously unreliable
00:48:42.800 you know even in everyday language we we know what we mean when we say you're just fooling
00:48:48.160 yourself or the content of those ideas is incompatible with empiricism with the idea that
00:48:57.920 knowledge reliable knowledge comes from the senses and I think what people regard that as just
00:49:04.880 one of those things you know it's it's one of the mysteries of nature it's it's the problem of
00:49:09.920 induction or something like that and you say it's hard to imagine what people mean when they
00:49:17.280 when they talk about direct observation it's interesting that that concept of direct observation
00:49:24.560 also had to be invented at one time yeah and in fact it was quite a liberation when it was first
00:49:30.480 invented like in various stages there were there was empiricism in the John Locke sense
00:49:38.240 is relatively recent but but the idea that we can gain knowledge by looking at the world which
00:49:45.680 is false was these concepts of knowledge and looking and reliable and that kind of thing they're
00:49:52.640 not built into our genes somebody invented those concepts and at the time when they invented them
00:49:58.880 they were an improvement on something that was more vague and more false than that trust the
00:50:05.040 authority or something for example yes but there was a time when you didn't even have to say trust
00:50:11.600 the authorities when trusting the authorities was just the way that the world was and nobody
00:50:18.240 bothered to put that into words and it was that reminded me of the divine right of kings which is
00:50:23.440 a concept that was invented only after the authority of kings was questioned yes well this all
00:50:31.680 raises the fact that there is this creativity going on this creation of concepts in order to try and
00:50:39.200 come to better understand the world yeah that is the uniquely creative capacity of the human mind
00:50:46.400 and mind itself how do you understand the nature of mind I sometimes think of it as this abstraction
00:50:52.880 I think you've said this to me it's a it's a it's a it's a funny kind of abstraction it's an
00:50:57.840 abstraction that itself needs to be instantiated in matter but also needs to be running it can't
00:51:03.840 just be like any other piece of knowledge which you can transmit from one place to another in different
00:51:09.760 physical forms and that's one way of understanding what knowledge is it allows itself to continue
00:51:14.960 to persist over time to get itself copied to get itself replicated but our mind a human mind
00:51:21.360 this thing that is enabling the creation of this knowledge it itself is an unusual kind of
00:51:28.560 abstraction how do you think of it at the moment yes so it's an unusual kind of of knowledge so we
00:51:34.640 have yet another classification a mind is a kind of a kind of knowledge you might say but it's a
00:51:41.680 kind of knowledge that doesn't only have to be instantiated but as you have just said it has to be
00:51:47.520 running now what does that mean running how fast running in what because running in the wrong kind
00:51:56.960 of computer would make it gibberish or in a kind of computer that has the wrong mapping to reality
00:52:04.960 we don't know how it works we don't know how the mind so the mind is characterized by creativity
00:52:10.720 I think we can go that far at least the human mind is characterized by creativity
00:52:15.680 but we don't know what creativity is we don't know what the distinction is between a computer
00:52:21.280 program that is running creatively and one that is not running creatively one day we will know
00:52:27.680 but we don't know yet I think also there are and again minds that minds exist is common sense
00:52:35.440 even though we don't know how they work or what specifically they are so more recent ideas that
00:52:41.280 maybe minds don't exist that had to be invented too it is not at all common sense and it doesn't
00:52:49.360 at all follow from any good philosophy but we don't know and one of the things I think that is a
00:52:57.440 misconception that dates from a very long time ago is that a mind is like mostly consistent
00:53:06.720 that it consists of the ideas in a mind are mostly consistent and when they're inconsistent that's
00:53:14.160 a kind of emergency and we have to fix that because because that means that it's not a proper
00:53:21.840 mind really it's it contains inconsistencies rather and therefore that's no different from
00:53:31.840 a load of propositions written down on a piece of paper I don't think that's true at all I think
00:53:38.880 a better way to think of the mind is as a set of problems and a problem consists of conflicting
00:53:46.000 theories so or rather a problem is is more like some conflicting theories that we have noticed
00:53:53.520 because we don't really think of something as a problem unless it's giving rise to some thought
00:53:59.040 so but but there must be ideas that are conflicting with each other before we have noticed it
00:54:05.600 and so the mind I think that is sort of massive tangled ideas which are largely inconsistent
00:54:13.040 the parts of it which we have sorted out into a kind of consistency are a minority
00:54:21.200 that are currently not giving rise to any thought they they might be invoked in some
00:54:27.920 thought that's about some other inconsistency but the part of the mind that is thinking
00:54:34.160 is full of inconsistency and so therefore a model of the mind that thinks of the mind as a set
00:54:41.440 of consistent propositions with occasional inconsistencies that we then fix it is I think very far
00:54:50.960 from the truth it's it's not a set of consistent ideas and it's not a set of propositions because
00:54:59.200 propositions have a definite truth value they each proposition is either true or false and it has
00:55:05.920 a perfectly definite meaning if it has a meaning whereas the ideas in minds don't have a definite
00:55:13.120 meaning and they're not precisely true or false we can make them have as sharp a meaning as our
00:55:20.560 current problem situation requires that's what we should be aiming for and we can make them as
00:55:26.880 consistent as the current problem situation requires and we're striving you talked earlier about
00:55:34.640 truth we're striving to make them as true as the current problem situation requires yes so it
00:55:41.840 sounds that whatever the nature of the mind is in a computational sense has to be radically
00:55:49.760 different to any other kind of program that we've hitherto encountered because all those other
00:55:57.040 programs are written in such a way that it's proposition after proposition perhaps one following
00:56:03.520 from another it's an algorithm of a kind and these statements need to be consistent or the
00:56:09.840 computer program itself isn't going to run but you're saying that it's possibly the case that
00:56:15.440 underlying this uniquely creative capacity of the human mind is something that is quite the mirror
00:56:21.440 image of that in in at least some respects and maybe this is this is what is needed in order to
00:56:27.600 go some way to explaining what's going on here with creativity or another way that you've
00:56:35.200 put that in the beginning infinity is of course explanatory universality this idea that
00:56:41.920 even if there were other kinds of creativity prior to us what we have is a kind of creativity
00:56:49.840 which allows us to create knowledge which is going to be able to solve problems in principle
00:56:56.720 about anything that exists in the physical universe which brings me to one of my little hobby
00:57:01.760 horses which is this concept that people sometimes raise that well there might be snailions out
00:57:08.400 there the super advanced aliens who are going to have some successor to the successor to the
00:57:13.760 successor of the unification of quantum theory and general relativity and even if they could
00:57:18.240 bring it to us we wouldn't understand it it would be written in a mathematics that's too complicated
00:57:24.240 for us or consists of concepts that are beyond our puny human minds to understand either that or
00:57:31.040 you know the super intelligence is going to come along at some point in the future and it too
00:57:35.440 is going to recognize that it's so much smarter than us and we probably all deserve to be exterminated
00:57:40.960 something like that what's wrong with these I think quite commonly held views about other kinds
00:57:48.560 of minds, super advanced alien minds or super intelligent artificial intelligences again of course
00:57:54.800 we can't prove that such things don't exist there's a very famous one called God which there have
00:58:02.000 been disputes about for many centuries they have yes I mean even the Bible speaks of unbelievers
00:58:16.240 so they must have existed right yes and to be a believer in that kind of entity means that
00:58:25.840 you're believing in an entity whose mind whose mental processes are first of all not embedded
00:58:34.000 in physics not instantiated in physics in in the same way that hours are and also that they can
00:58:40.720 reach further they can understand things that things embedded in mere physics can never understand
00:58:47.600 and you can't prove that's false but it is a bad explanation as I point out in the beginning of
00:58:55.280 infinity and so one thing is that there are many such theories and there are many theories about
00:59:02.800 such entities whether they be snailions or gods or devils or demons or artificial general
00:59:11.680 intelligences those theories since they're bad explanations they have the property that if two
00:59:18.880 people such believers in different ones come to persuade me of their view then there's nothing
00:59:26.320 I can do to choose between them it's it's like they are invoking some non understandable thing
00:59:33.440 and the two of them are invoking some two non understandable things with a non understandable
00:59:39.440 difference between them so I would like to you know put both those people into a sack and tie it
00:59:46.560 shut and then only have to debate with the survivor for efficiency very good so that that's related
00:59:56.400 to this idea that again problems are soluble and what I would suggest is that a kind of a special
1:00:02.320 case of that almost is that the all evils are due to lack of knowledge principle of optimism
1:00:08.240 that you have but here it's really interesting the principle of optimism this claim that all evils
1:00:13.840 are due to a lack of knowledge seems to be linking quite strongly epistemology stuff about knowledge
1:00:20.480 to evil stuff about morality isn't that a big leap surely people who do evil things are doing
1:00:27.920 evil things because of their ideas which is to say what they know it's not a lack of knowledge is
1:00:33.200 it's it's a it is the presence of some knowledge oh well that's the same thing they are doing it
1:00:40.560 because their knowledge is inadequate is false in some relevant way and even the the good guys
1:00:48.480 their knowledge is better than the bad guys but it's still not true it's not perfect it can be
1:00:55.920 improved the good in fact the good guys are characterized to a large extent by the fact that they
1:01:02.000 are open to correcting their existing knowledge and to adopting better ideas that they previously
1:01:08.800 didn't know yes I think it's the it's the natural thing it should be one's first guess that
1:01:16.400 moral knowledge is included in the same epistemology as physical or mathematical knowledge
1:01:23.120 because as I've said the arguments that there are different kinds of knowledge depending on
1:01:29.360 some kind of privilege access to one or the other is just a mistake it's it's you know
1:01:35.600 empiricism or something of the kind that that is is just a not understanding the
1:01:42.640 conjectural nature of all ideas yes and that include must include moral ones and mathematical
1:01:49.840 ones and physical ones and and so on and uniformly the way to get better ideas is to try to
1:01:56.160 get better explanations in the light of the problems that one has with those ideas there might
1:02:01.760 be I think there's even another way that the beginning infinity does create a strong link in one's
1:02:09.040 mind between epistemology and morality and that would be in the moral injunction do not destroy
1:02:15.760 the means of error correction so there we have you know error correction that's epistemology and
1:02:21.440 do not do this thing okay so there's a moral claim now I wanted to focus on this for a minute
1:02:27.120 because this might raise an issue within constructor theory and that this is your new physics
1:02:33.760 along with your new theory of physics along with kiaramiletto about the physics of the possible
1:02:38.720 in the impossible or the possible in impossible transformations I think is one way it might be described
1:02:44.640 and among many things to be excited about with this approach is the link it seems to me between
1:02:50.240 physics and epistemology and we already know some of this story we know that what can be proven
1:02:56.640 in mathematics depends on what we know about what the laws of physics are and how the laws of
1:03:00.800 physics operate and because we know that proofs in mathematics are a kind of computation computation
1:03:05.600 requires a computer the computer has to be made out of something they made out of matter the
1:03:09.520 matter obeys laws of physics so we can only prove things that the laws of physics say it is
1:03:14.160 possible to prove but constructor theory seems to be generalizing this further I'm not sure if
1:03:19.360 that'd be fair to say so we're going beyond mathematics now and perhaps into realms where we are
1:03:24.720 saying look some things are not possible to know and some things are possible to know even outside
1:03:29.840 of mathematics but there may be things impossible to know in history for example for in science
1:03:34.880 because there will be no transformation allowing us to actually construct the knowledge that
1:03:39.760 solves the problem there but this if I've just gone way off the rails in my reasoning here
1:03:45.360 would seem to contradict the problems a soluble claim in the beginning infinity though the one
1:03:51.200 example I want to call on I think you might have mentioned this in the fabric of reality I can't
1:03:55.840 remember but it's something to the effect of let's say you wanted to know what Augustus
1:04:01.280 Caesar ate on his 13th birthday that's a reasonable scientific question but it might also be
1:04:07.520 unknowable but it's not going to be a problem for our understanding because it's going to be
1:04:13.360 inherently uninteresting it's not going to solve any actual historical problems but is this
1:04:18.400 why of thinking about how constructive theory comes to bear on morality and epistemology at all
1:04:26.160 valid I think that one can address that issue without using constructive theory directly
1:04:33.680 if constructive theory works then there will be a theory of knowledge within constructive theory
1:04:39.520 just like there will be a theory of quantum mechanics within constructive theory we don't know how
1:04:44.560 these subsidiary theories whether these subsidiary theories will be changed or if they have to
1:04:51.280 be changed to what extent they have to be now theory of knowledge is nowhere near as precise
1:04:57.280 and accurate as theories about physics I don't quite understand your question because
1:05:04.480 suppose we had a problem about Caesar's what Caesar ate on his 13th birthday I think the example I
1:05:12.080 usually use is Julius Caesar's last meal yes yes never mind I mean Augustus Caesar's 13th birthday
1:05:18.560 meal is just as good if some problem depended on knowing that as a solution then it's not accurate
1:05:30.560 to cast this problem in terms of having to have evidence of what it was you know this is not
1:05:38.960 necessarily a question of which observables can be observed in physics we know that most of the
1:05:46.080 observables the detailed observables of the past are have been randomized to such an extent that it
1:05:53.440 would require an infeasible amount of collection of knowledge an infeasible amount of measurement
1:06:00.000 shall we say to to reconstitute it and that might well be true I mean if it isn't true of
1:06:06.240 of these Caesar meal events it'll be true of some lots of events it'll be true of most events
1:06:13.840 at the time so assume that it is infeasible because of the laws of physics and this could be
1:06:23.120 expressed precisely in constructive theory to measure Julius Caesar's last meal that doesn't
1:06:29.200 mean that we can't solve the problem that gave rise to this question because it can't be a
1:06:34.480 question about physics from from from the point of view of physics this is a very uninteresting
1:06:39.840 question so it would be a thing it would be a question about history or about sociology or about
1:06:47.040 you know some subject that has been invented yet in which there would be explanations that rival
1:06:52.720 explanations both of which had reasonable arguments in their favor and which somebody decided could
1:06:58.880 be resolved by making this measurement and then it turns out this measurement is impossible well that
1:07:04.480 doesn't mean that it can't be resolved in other ways yes I mean we we know that that last meal
1:07:12.320 was not a cheeseburger and that is not because we have measurements to that effect
1:07:20.720 it's because we have a high level theories about the development of human culture and the problem
1:07:27.280 about what he ate etc would have come out of that kind of field yes precisely if it will
1:07:36.800 when may well come out of that kind of field as well yeah I can only imagine that the question
1:07:41.760 would arise if there was a problem about how and why he died so if it was Julius Caesar and there
1:07:48.800 was some concern that maybe he'd been poisoned just before he died well then there would presumably
1:07:54.800 be theories about you know existing historical documents about how various other people living
1:08:02.400 with him at the time didn't particularly like him and then presumably although we might not be
1:08:06.160 able to tell what his final meal was some very smart forensic scientist might be able to detect
1:08:11.600 some kind of toxin in where his stomach used to be so I imagine that even a problem like this
1:08:17.520 it wouldn't be framed in exactly those words what was his last meal but it might be
1:08:22.880 you know some some others kind of historical questions I mean it would arise out of some problem
1:08:28.960 that wasn't a physics problem for sure yes but by the way there is this problem with Napoleon you
1:08:34.800 know did he die of wallpaper right because you know it's it's controversial how Napoleon died
1:08:44.080 he wasn't that old and he had some symptoms which are consistent with arsenic poisoning
1:08:52.080 and there were people who would would have preferred to see him dead and then other people
1:08:58.880 who said well yes it was arsenic poisoning but it was because of the wallpaper the color of the
1:09:06.000 wallpaper was was caused by arsenic paint and other people who said yes so there was arsenic in
1:09:13.200 the wallpaper but not enough to kill him and so on and so on and this this problem is
1:09:18.240 eminently addressable not by going and finding video evidence of the poisoning okay so
1:09:25.920 following proper and like myself and I was in that tradition we don't place any real currency on
1:09:30.800 the source of an idea because any idea can be evaluated utterly independent of its source or its
1:09:35.520 author and I can take all that on board I think you go even further in this that you're not
1:09:40.560 even interested much in the origin of ideas or the history of ideas and this is actually encapsulated
1:09:46.320 in what Naval has been pains to point out in his podcast with me anyway at least not much
1:09:51.440 interested in names who said what and so on it's basically about the ideas and I think that's
1:09:55.600 quite right nevertheless personally and I guess is a point of indulgence for anything else
1:10:00.800 I am interested in the history of ideas to some extent so you know I like to know the fact that
1:10:05.360 Einstein really was the primary generator of general relativity but it's interesting to know that
1:10:09.920 Marcel Grossman for example helped him and you know I think one or more of his wives might have
1:10:15.280 helped him as well with the mathematics on general relativity so it's it's interesting historically
1:10:20.480 about how these great theories kind of came to us what the lineage is now that brings me to
1:10:27.280 this question about quantum computation I'm interested in this because you were inspired obviously
1:10:33.200 by Turing and your paper as of I think it was last week anyway it's now been cited 6122 times
1:10:41.360 which is no small feat that that paper being titled quantum theory the church cheering
1:10:46.560 principle in the universal quantum computer what I wanted to ask you about that is as you wrote
1:10:52.240 it because I think when Turing wrote his paper on the Turing machine he was thinking well to
1:10:56.880 an abstract mathematical object this isn't going to have much I don't know it did he think it
1:11:02.640 was going to have much in the way of a huge industry of engineering these things was going to
1:11:09.040 follow I don't know if that was in his mind but did you have any sense in writing the paper
1:11:13.600 about quantum computation that it would have spawned an industry a multi billion dollar at the
1:11:19.280 moment industry of racing to build these things did that into your mind at the time no I was entirely
1:11:29.120 concerned with the laws of physics and that this was a hitherto
1:11:36.400 unsuspected facet of quantum theory that it had this intimate relationship with computation
1:11:44.320 so I had in the back of my mind that maybe this could be built a quantum computer could be built
1:11:52.160 for the purpose of demonstrating or testing properties of the laws of physics of quantum theory
1:11:58.800 but I wasn't concerned with practical uses of it at all and not even other laboratory uses of
1:12:07.520 it and by the way I think I'm not a so I'm not a historian of science I don't know much about
1:12:14.880 the history of ideas in general yes only certain very narrow facets I but I think that history
1:12:23.920 in general is an extremely important worthwhile subject and the history of ideas in particular
1:12:30.160 is I think the most important aspect of history it's just that I happen you know to to have
1:12:38.240 studied other things mostly but I think that Turing was also not interested at the time when
1:12:46.400 you wrote that paper in making anything useful. Babbage interestingly was yes and the for him
1:12:58.240 the again I'm going by TV documentaries rather than any real research of my own but it seems that
1:13:06.960 that he was initially concerned with a very practical application of computers
1:13:13.680 namely the autumn automation of the printing of mathematical tables which had to do with navigation
1:13:21.120 and so on and that he even when he conceived of the universal version of this machine which
1:13:29.600 was then called the analytical engine he still wasn't then what he saw was this this was a
1:13:36.240 universal machine for arithmetic and for algebra but or not even for algebra I'm not sure
1:13:42.160 for for arithmetic at least and it was lovelace who saw that this machine would be universal
1:13:49.680 in the sense that we mean today. Yes yes and so that then that leads me to the question that
1:13:56.880 I don't know I don't want it to be too uncomfortable but there is this question about
1:14:00.960 was it church was it cheering and now of course you bring in Babbage as well and love
1:14:05.360 lace you say is with the first to figure out that these machines could be universal well to what extent do
1:14:11.520 you think Feynman understood the universality of quantum computation did he have a conception of it
1:14:19.760 at all around the time when you were writing this paper or was it only in light of you telling him
1:14:26.480 about the proof that he then sort of got what you were going on about I don't know I only met him once
1:14:33.280 and we had a long conversation only part of which was about quantum computation and and I was not
1:14:42.880 at all focused on finding out what he knows right okay yes so I don't know but I know that in his
1:14:52.560 published work there is no real hint of the thing that is now called a universal quantum computer
1:15:00.640 or actually it's now more often called the universal quantum Turing machine which is a very
1:15:06.320 bad terminology but there's although he again he was aware that quantum computation could be
1:15:15.440 more powerful than classical computation and he was aware of a certain level of universality
1:15:21.760 but his idea for how to make one of these was itself to put on some kind of circuit board
1:15:32.560 a quantum system that had specially tuned Hamiltonians whereas the in the real quantum computer
1:15:41.600 the special tuning is itself a quantum program it's there's a single machine you don't have to
1:15:47.920 change the hardware to make to make to compute a new quantum computation there is a single
1:15:55.840 machine that can be programmed to enact any quantum computation and I don't think in I don't
1:16:03.200 think there's any hint of that in Feynman's published work although the speed with which he
1:16:09.680 costened on to the algorithm that I explained to him suggests that he was on the verge of that either
1:16:17.360 before I spoke to him or just after okay two final just purely for fun questions but yes but as you
1:16:26.960 said who cares this is true this is true except for historians of science I'm sure in the
1:16:33.760 the years and decades to come this will be a certainly a point of interesting in future they'll
1:16:39.760 analyze the wallpaper and find out yes okay this question just purely for fun do you have any
1:16:48.400 opinion on tic-tacs that's a big thing going on at the moment and do you know what I'm talking
1:16:52.720 about no I don't know what it is okay so this is the the American military specifically I think the
1:17:00.480 Navy who've released these videos of what they say are unidentified objects of some kind
1:17:08.320 and I know this is ridiculous they say things like their violating laws of physics or at least
1:17:15.200 they are evidence of technology which is not explicable given the current state of technology
1:17:23.280 you haven't heard about these things seen anything about these things no have any opinion on these
1:17:27.360 things well now that you mention it I've seen things on Twitter right are now explicable in the
1:17:33.680 light of is it the American military or something having having said something about your
1:17:40.480 foes yes I see okay well the opportunities for error are enormous and to perform a scientific
1:17:52.880 experiment there is a crucial test of sophisticated scientific theories is very very difficult
1:18:01.680 and universally almost universally underestimated it's sort of taken for granted that Einstein did
1:18:09.120 a very difficult thing but it's not so much understood the stern and gurlach who did experiments
1:18:16.560 on quantum superpositions of particles in different positions and they did an amazing thing as well
1:18:22.160 yes good experiments are rare and they require usually a great deal of skill and creativity
1:18:33.200 and it's not the kind of thing that military pilots or policemen are typically cognizant of
1:18:44.960 yes so I think when people like that report a thing that quote violates the laws of physics
1:18:53.840 I would consider it unreasonable to go for any explanation of that other than human error
1:19:01.840 yes yes and of course when you do look at the footage there is no apparent violation laws of
1:19:07.600 physics even if you grant that this thing is moving at a high velocity beyond anything that
1:19:13.200 we might be capable of that's still sub light speed so it has a violated relativity on the one
1:19:18.960 hand and by the way even if you don't have an answer for what's going on there well that's kind
1:19:24.560 of where you might have to stop you don't immediately lead to it's aliens from the other side
1:19:29.440 of the galaxy my last question is from my father and I'll just ask you this before I go it's about
1:19:35.840 dark energy and we know the universe is accelerating in its expansion it's behaving as if
1:19:44.080 there is negative pressure on the outside of the observable universe isn't this evidence that
1:19:49.920 the observable universe is actually inside of a much larger region itself of lower density but
1:19:58.720 magnificently greater size perhaps infinite in size and perhaps it's actually got zero density perhaps
1:20:03.520 is void beyond our universe is the thing into which the universe is necessarily expanding because
1:20:09.120 of a positive pressure inside of our universe and outside of that outside of our universe that's
1:20:13.360 negative pressure could this be a solution so first of all dark energy is just the name given to
1:20:19.520 this anomalous expansion which we haven't explained yes so I think the reason that dark energy
1:20:25.440 was chosen as a name is because of dark matter where the all reasonable theories of it so far
1:20:33.600 have postulated that it's a kind of matter and it's dark because because it doesn't interact
1:20:39.120 with photons and so on with dark energy we don't have such a thing we we don't know that there
1:20:45.440 is a source of pressure or that these observations are caused by something pushing on the universe
1:20:51.040 and so on but with the prevailing theories of what dark energy does never mind what it is but what
1:20:59.200 it does the universe is not expanding into anything the universe is is the length scales in the
1:21:08.240 universe are increasing intrinsically and this is the same same as was the case with the with the
1:21:17.200 prevailing theories before dark energy that the universe initially had well at any rate very near
1:21:24.960 to the big bang it was very small there was a time when it was only the size of an atom there was
1:21:30.320 a time when it was only the size of a neutron and so on and at that time and now it's much bigger
1:21:36.560 the difference between then and now is not that it has expanded to fill a void it has just
1:21:42.720 expanded intrinsically yes and some of the present theories say that it is in fact infinitely
1:21:50.160 large and that it is infinitely large and homogeneous so that the the total amount of matter
1:21:58.320 in it is infinite I don't think that there are any theories I mean one could easily write down
1:22:05.280 a theory in which the universe was inhomogeneous and we are in the only place in it that has matter
1:22:12.320 right yes that wouldn't help in any way with any of the existing theories and more generally by
1:22:17.520 the way theories of inhomogeneity in the universe as far as I know I'm not an expert on this but
1:22:25.280 I think they've only been invoked by people who want to say that there is no dark energy that
1:22:30.320 it's just a coincidence caused by inhomogenities excellent okay I think that absolutely
1:22:37.040 answer the question I think that will do for now but I hope not for the last time I make my
1:22:41.280 through the fabric of reality after all now at the moment so perhaps at the end of that we can
1:22:46.000 speak again if not sooner so thank you very much for writing the book so I think they've been
1:22:53.840 well the explanations are transformed the world I think they've been life transforming for many
1:22:57.840 people so it's been wonderful to talk to you very gratifying today to have this conversation
1:23:03.440 so have a wonderful remainder of the day yourself same to you it's always fun chatting
1:23:13.840 so there we go I hope you enjoyed that I certainly did as I say I'm working on what might be
1:23:19.600 called interview technique it's a steep learning curve the content of Deutsch and Poppers Uvoire
1:23:25.360 is deep and subtle enough but adding to that how to run a podcast and being surrounded by new
1:23:31.040 upgraded podcast hardware and software that I'm struggling to learn to use there's a whole other
1:23:36.640 thing but hopefully will improve rapidly over the coming weeks and months if you're a new listener
1:23:41.680 I'd encourage you to go out and to listen to all of the David Deutsch content that is out there
1:23:46.560 his TED talks and other interviews of course buy his books subscribe to my podcast here wherever
1:23:52.160 you're listening there is a YouTube version as I say if you are on audio only which sometimes has
1:23:57.040 those pretty visuals subscribe to the Naval podcast where we are exploring all the major themes
1:24:03.280 in the fabric of reality and the beginning of infinity and Naval is broadening all that content
1:24:09.520 out into the realms of wealth wisdom and life and finally if you're someone client go to
1:24:15.520 www.brethall.org and follow the links there to support this podcast there are lots of great
1:24:22.160 podcasts out there all about science and philosophy and even thinking but I think here we have a
1:24:28.400 small community uniquely devoted to a particularly special kind of clear thinking about life
1:24:35.360 informed by the best that science and philosophy can teach us we'd like to grow so the ideas can
1:24:41.280 reach into places where the errors need correcting so I'll keep doing my bit until next time
1:24:46.080 let me steal a line from Naval and say stay optimistic bye-bye
