00:00:00.000 Welcome to Topcast, and to episode 106, which is part 2 of chapter 4 of the fabric of reality,
00:00:09.040 criteria for reality. And in the last part, we went through a refutation of solipsism and the various
00:00:16.640 other, what one might call metaphysical theories about ultimate reality. Namely, that realism
00:00:23.920 might not be true because perhaps it's all a dream going on in your head or perhaps it's a
00:00:29.280 simulation going on in a computer or perhaps it's the machinations of an evil demon. Whatever the case
00:00:35.120 might be, realism might not be false. How can we rule this out? And we were talking about the fact
00:00:40.640 that no scientific experiment can falsify that kind of theory, that kind of strange claim
00:00:48.240 that reality itself might be utterly different from what we experience or what our science is telling
00:00:54.160 us the truth of the matter happens to be and that all of our supposed good explanations are
00:01:00.320 actually bad explanations based upon the fact that ultimate reality is all going on in the
00:01:05.360 mind of a dreamer. It seems we can't rule that out logically and we can't rule that out scientifically
00:01:11.680 either. So what can we do? Well, what we can do is what we did do in the last episode and in the
00:01:18.480 fabric of reality, David goes through a refutation, not a scientific falsification,
00:01:23.840 not a logical disprove, but a philosophical refutation. An explanation that these explanations are
00:01:30.800 bad explanations and where we finished was with David saying in the fabric of reality and I'll
00:01:35.680 quote again, quote, so we can continue. Reassured with common sense realism and the pursuit of
00:01:41.760 explanations by scientific methods, but in the light of this conclusion, what can we say about
00:01:46.720 the arguments that made solipsism and its relatives superficially plausible, namely that they
00:01:52.960 could neither be proved false nor ruled out by experiment. What is the status of those arguments
00:01:57.920 now? If we have neither proved solipsism false, nor ruled it out by experiment, what have we done?
00:02:04.240 And David goes on to say, there is an assumption built into this question. It is that theories
00:02:09.760 can be classified in a hierarchy, mathematical, to scientific, to philosophical, of decreasing
00:02:17.760 intrinsic reliability. Many people take the existence of this hierarchy of a granted despite the
00:02:23.520 fact that these judgments of comparative reliability depend entirely on philosophical arguments,
00:02:29.200 arguments that classify themselves as quite unreliable. In fact, the idea of this hierarchy is a
00:02:34.960 cousin of the reductionist mistake I discussed in chapter one. Namely, the theory that microscopic
00:02:40.720 laws and phenomena are more fundamental and emergent ones, pausing their my reflection. We learn this
00:02:47.600 in school. And in fact, mathematics teachers are quite proud of the fact that they can say to the
00:02:53.520 other teachers of other subjects, we have privileged access to teaching certainty, to teaching
00:02:59.440 mathematical, logical certainty in our classes. And they really take this seriously, I suppose,
00:03:05.440 they get it from their lecturers as well. So it bleeds into culture because it's kind of there in
00:03:10.240 the schooling system that mathematics is taught has been absolutely certain on a firm foundation.
00:03:16.240 But of course, this very claim that mathematics is certain that it has built upon a firm foundation
00:03:23.040 and infallible way of getting at the truth. That very claim is itself a philosophical argument.
00:03:29.360 It's false. It turns out that it's false. But the mean fact that we're trying to
00:03:32.960 admit that anyone would be trying to make that argument should reconsider the fact that they're not
00:03:37.360 getting there by a mathematical proof, which is supposedly the only way to get to absolutely
00:03:43.360 certain truth. So if the argument for mathematics has the only privileged access to absolutely
00:03:49.600 certain truth, but that argument itself is based upon a philosophical claim, which itself,
00:03:54.880 supposedly, is nothing but a mere matter of opinion, we've got a problem. And of course,
00:03:59.680 in the David Deutsch fallibleist worldview, we're going to do away with all of that,
00:04:04.080 and we're simply going to regard each of the different domains of our inquiry, call them what
00:04:08.480 you want, mathematical, scientific, philosophical. As all unequal footing in a sense,
00:04:13.680 all part of an interconnected web of knowledge and interconnected web of fallible guesses about
00:04:19.040 the nature of reality. So let's go on to see what David says next about this.
00:04:23.120 Quote, the same assumption occurs in inductivism, which supposes that we can be absolutely
00:04:29.040 certain of the conclusions of mathematical arguments because they are deductive reasonably sure
00:04:35.200 of scientific arguments because they are inductive. And forever undecided about philosophical
00:04:40.800 arguments, which it sees as little more than matters of taste and quote, and isn't that the
00:04:46.000 truth? I mean, not only do we pick that up in school, it's something that I think almost everyone
00:04:51.600 lives with all the time, unless they've encountered the work of Popper and Deutsch and associated
00:04:56.640 ideas, but you don't have to step very far outside of the popularian worldview or the worldview
00:05:02.800 presented in the fabric of reality, the beginning of infinity, before you get this as simply common
00:05:08.320 sense, this idea that as David says there in that paragraph, mathematical arguments are certain
00:05:14.960 because they're deductive. So you can be sure of them and you can be almost sure of scientific
00:05:20.400 arguments because they're inductive. And as the philosophy, well, that's just a mere matter of opinion
00:05:25.360 more or less. So I'm skipping about a paragraph and David goes on to say, quote, the rejection
00:05:30.080 of mere explanations on the grounds that they are not justified by any ultimate explanation, inevitably
00:05:36.800 propels one into futile searches for an ultimate source of justification. There is no such
00:05:42.400 source, nor is there that hierarchy of reliability from mathematical to scientific to philosophical
00:05:49.120 arguments. Some philosophical arguments, including the argument against solipsism are far more
00:05:55.200 compelling than any scientific argument. Indeed, every scientific argument assumes the
00:06:00.400 falsity, not only of solipsism, but also of other philosophical theories, including any number
00:06:06.000 of variants of solipsism that might contradict specific parts of the scientific argument. I shall
00:06:11.760 also show in chapter 10 that even purely mathematical arguments derive their reliability
00:06:17.680 from the physical and philosophical theories that underpin them, and therefore they cannot,
00:06:23.120 after all, yield absolute certainty. Having embraced realism, we are continually faced with
00:06:28.960 decisions as to whether entities referred to in competing explanations are real or not, deciding
00:06:34.560 that they are not real. As we did in the case of the angel theory of planetary motion,
00:06:39.200 is equivalent to rejecting the corresponding explanation. Thus, in searching for and judging
00:06:43.760 explanations, we need more than just a refutation of solipsism. We need to develop reasons for
00:06:49.280 accepting or rejecting the existence of entities that may appear in contending theories.
00:06:54.480 In other words, we need a criterion for reality. We should not, of course, expect to find a final
00:07:00.720 or infallible criterion. Our judgments of what is, or is not real, always depend on the various
00:07:05.920 explanations that are available to us, and sometimes changes our explanations improve just
00:07:11.680 pausing their more reflections. So what David is going to come to here in the fabric of reality
00:07:17.760 is that our criterion for reality is whether or not an entity kicks back, and we'll have more
00:07:23.280 to say about this. This is Dr. Johnson's criterion. And whether something kicks back is about whether
00:07:29.200 it behaves autonomously, unpredictably, in a complex way, in a way that would require, if it was
00:07:35.520 going to be an illusion, computationally, highly complex in order to simulate, in order to give
00:07:42.240 us the appearance of that thing. But later, of course, in the beginning of infinity, I think we get
00:07:46.640 a more parsimonious version of this, which entails all of those other ways in which we explain
00:07:51.600 whether a thing is real or not, whether a thing exists or not, where we say a thing is real,
00:07:56.160 or a thing exists to the extent that it appears in our best explanations of reality.
00:08:02.160 If and only if, it appears in those explanations. So I'll pick it up by David says, quote,
00:08:07.680 not only do explanations change, but our criteria and ideas about what should count as an
00:08:14.080 explanation are gradually changing, improving, too. So the list of acceptable modes of explanation
00:08:20.240 will always be open-ended, and consequently, the list of acceptable criteria for reality
00:08:25.600 must be open-ended, too. But what is it about an explanation given that for whatever reasons
00:08:31.920 we find its satisfactory, that should make us classify some things as real and other things
00:08:37.120 as illusory or imaginary? James Boswell relates in his life of Johnson, how he and Dr. Johnson
00:08:43.840 were discussing Bishop Berkeley's solipsistic theory of the non-existence of the material world.
00:08:49.920 Boswell remarked that although no one believed a theory, no one could refuse it either.
00:08:54.800 Dr. Johnson kicked a large rock and said, as his foot rebounded, I refused it thus.
00:08:59.680 Dr. Johnson's point was that Berkeley's denial of the rock's existence is incompatible with
00:09:05.200 finding an explanation of the rebound that he himself felt. Solipsism cannot accommodate any
00:09:10.960 explanation of why that experiment or any experiment should have won outcome, rather than another,
00:09:15.760 to explain the effect that the rock had on him, Dr. Johnson was forced to take a position on the
00:09:20.240 nature of rocks, were they part of an autonomous external reality, or were they figments of his
00:09:24.720 imagination? In the latter case, he would have to conclude that his imagination was itself a vast
00:09:31.120 complex autonomous universe, causing their mind reflection. So Bishop Berkeley, or Bishop
00:09:35.360 Berkeley, however we pronounce it, he had this vision of idealism, idealism, meaning that
00:09:41.840 what is apparently happening in external reality isn't really it's just all ideas, it's going on
00:09:47.600 inside your head. But what Johnson would say about that, what Dr. Johnson would say about that,
00:09:52.320 is if you kick a rock and reliably, the same experience as happening again and again,
00:09:57.600 you're effectively doing a scientific experiment in order to test theories about what happens when
00:10:03.440 you kick rocks, and your foot continues to rebound, why should it have this consistent character?
00:10:08.640 Why should there be this autonomous way in which your imagination behaves consistently over time?
00:10:15.120 You would have to concede that your imagination is itself this extremely complex thing,
00:10:21.440 which behaves according to physical laws that one can discover. And as we say, that means that
00:10:27.600 your idealism, Bishop Berkeley's idealism, this idea of solipsism, or whatever you like, is
00:10:32.560 nothing but realism. The claim that there really is an external autonomous reality, which you
00:10:38.080 cannot simply imagine into existence, you cannot imagine into existence the behavior of different
00:10:44.000 things, but rather you have to go out into the world and investigate things to find out
00:10:47.760 how they're going to behave, namely by kicking them. If it was all just in your imagination,
00:10:52.800 we should expect that each time you kick the rock, something different might happen. Sometimes
00:10:57.200 your foot might rebound, sometimes it might go through it, sometimes the rock might disappear,
00:11:01.040 sometimes the rock might turn into a rabbit and so on and add in for an item. But the fact that
00:11:06.160 the rock behaves in a predictable way, and the fact that we can learn about the properties of rocks
00:11:11.760 and so on and so forth for every other object in our external reality, means that it can't just
00:11:18.400 all be in your imagination, or if you postulate that all you're saying is that your imagination
00:11:23.280 is equally as complex and subject to physical laws as real physical realities. And so you are
00:11:31.760 just saying that realism is true, plus the assumption that you're dreaming that physical reality
00:11:37.600 and of existence. So it's a needless philosophical assumption. There it goes on to say after a paragraph
00:11:43.280 that I'm skipping. Quote, but Dr. Johnson's idea is more than just a refutation of solipsism.
00:11:48.960 It also illustrates the criterion for reality that is used in science, namely if something
00:11:54.960 can kick back, it exists. Kicking back here does not necessarily mean that the alleged object is
00:12:00.240 responding to being kicked, to being physically affected as Dr. Johnson's rock was. It is enough
00:12:05.840 that when we kick something, the object affects us in ways that require independent explanation.
00:12:12.160 For example, Galileo had no means of affecting planets, but he could affect the light that came from
00:12:17.440 them. His equivalent of kicking the rock was refracting that light from the lenses of his telescopes
00:12:22.080 and eyes. That light responded by kicking his retina back, the way it kicked back allowed him to
00:12:27.280 conclude, not only that the light was real, but that the heliocentric planetary motions required
00:12:32.800 to explain the patterns in which the light arrived were also real. By the way, Dr. Johnson did not
00:12:38.160 directly kick the rock either. A person is a mind, not a body. The Dr. Johnson who performed the
00:12:43.280 experiment was a mind, and that mind directly kicked only some nerves, which transmitted signals to
00:12:49.360 the muscles which propelled his foot towards the rock shortly afterwards. Dr. Johnson
00:12:53.440 perceived being kicked back by the rock, but again only indirectly after the impact had set up a
00:12:58.240 pressure pattern in his shoe and then in his skin, and had then led to electrically impossible
00:13:02.160 in his nerves and so forth. Dr. Johnson's mind, like Galileo's and everyone else's, kicked
00:13:07.520 nerves and was kicked back by nerves and inferred the existence and properties of reality
00:13:12.880 from those interactions alone. What Dr. Johnson was entitled to infer about reality depends on
00:13:18.720 how he could best explain what had happened. Just pausing their my reflection. So this concept
00:13:24.720 of kicking back, obviously it's metaphorical in almost all situations, except when you're explicitly
00:13:30.240 kicking rocks, but even then as David says, it's not really you that are kicking the rock,
00:13:34.160 you are kicking the nerves inside of your brain. All that aside, what the kickback means is that
00:13:39.600 you are getting evidence, feedback from the external physical reality around you, and that external
00:13:46.640 physical reality is not merely bending to your will. It is sometimes behaving in completely
00:13:52.080 unpredictable ways as Galileo's discovery through his telescope was. I'm not sure if he
00:13:58.000 hypothesized that there would be definitely moons going around Jupiter, but when he saw that,
00:14:04.080 that was an unexpected kickback from reality. Galileo, by the way, was the first one to discover
00:14:10.400 moons orbiting Jupiter. Okay, so skipping a quite substantial part of the book now, a couple of pages,
00:14:17.520 and I'm picking it up where David says, quote, it is not how hard something kicks back that makes
00:14:22.960 the theory of its existence compelling. What matters is it's role in the explanations that such
00:14:28.480 a theory provides. I have given examples from physics where very tiny kicks lead us to momentous
00:14:34.960 conclusions about reality, because we have no other explanation. The converse can also happen.
00:14:39.920 If there is no clear cut winner among the contending explanations, then even a very powerful kick
00:14:45.520 may not convince us that the supposed source has independent reality. For example, you may one day
00:14:51.040 see terrifying monsters attacking you, and then wake up. If the explanation that they originated
00:14:55.760 within your own mind seems adequate, it would be irrational for you to conclude that there really
00:15:00.480 are such monsters out there. If you feel a sudden pain in your shoulders, you walk down a busy
00:15:05.200 street and look around and see nothing to explain it, you may wonder whether the pain was caused
00:15:10.080 by an unconscious part of your own mind, or by your body, or by something outside, you may consider
00:15:16.400 it possible that a hidden prankster has shot you with an airgun yet come to no conclusion as to the
00:15:21.440 reality of such a person. But if you then saw an airgun pellet rolling away on the pavement,
00:15:26.240 you might conclude that no explanation solved the problem as well as the airgun explanation,
00:15:32.080 in which case you would adopt it. In other words, you were tentatively infer the existence of
00:15:37.040 a person you had not seen and might never see, just because of that person's role in the best
00:15:42.800 explanation available to you, pausing their my reflection. Isn't that a wonderful little example?
00:15:47.200 As I have often said on this podcast, getting it straight from David Deutsch, we are usually
00:15:53.760 in science explaining the scene in terms of the unseen. This is what science is all about,
00:15:59.120 almost every single interesting phenomena in modern science is about explaining what we do see,
00:16:06.000 light, rocks, stars, etc, etc, matter around us. All the stuff we see is explained in terms of
00:16:13.200 things we cannot see, subatomic particles, nuclear processes going on inside of stars, the core
00:16:19.920 of the earth, evolution on time scales that we cannot observe, the movement of tectonic plates,
00:16:25.520 etc, etc. And this is not unusual even in day to day life, as David says there, you know,
00:16:30.480 you might very well have this experience of being shot by an airgun. Well, if that happens,
00:16:35.440 and you see the pellet rolling away, it would be the best explanation that someone that you might
00:16:40.720 never see, the unseen person must exist in order for you to have experienced what you experienced,
00:16:47.760 as David goes on to say, quote, clearly the theory of such a person's existence is not a logical
00:16:54.240 consequence of the observed evidence, which, incidentally, would consist of a single observation,
00:16:59.440 nor does that theory have the form of an inductive generalization. For example, that you will
00:17:04.000 observe the same thing again, if you perform the same experiment, nor is the theory experimentally
00:17:08.320 testable, experiment could never prove the absence of a hidden prankster. Despite all that,
00:17:13.600 the argument in favor of the theory could be overwhelmingly convincing if it were the best
00:17:19.040 explanation, pausing their my reflection. So this is what detectives and the legal system have to do
00:17:24.720 all the time. What they're doing is trying to explain one off events rather often. And when you
00:17:31.760 have these one off events, a particular murder, a particular assault, where you do not have the
00:17:36.640 murderer or you do not have the criminal in custody. And you might not even know who the person is
00:17:41.440 yet. Nonetheless, the best explanation has to be that a person did it that a particular person did
00:17:48.560 this thing, but you can't arrive at that conclusion based upon any kind of inductive claim. It's
00:17:55.760 not like you're going to be able to witness that same murder over and over again. You've got it
00:18:00.960 only one time. You're witnessing it only once and you will only ever witness it once. And there's
00:18:05.600 no experiment that you can do in order to demonstrate that a person, a particular person, did this
00:18:12.160 murder, but rather what we do is we gather evidence and then the best explanation of the evidence.
00:18:17.520 Our conjectures, which all come to bear on trying to explain this evidence, are then set against
00:18:23.120 one another in light of the evidence. And each of them ruled out until one of them, ideally,
00:18:29.280 explains all the evidence. And no piece of evidence is able to rule out a particular
00:18:35.200 murderer or criminal or whatever happens to be the case. So I guess what I'm saying there is,
00:18:39.520 if you want another refutation of inductivism, then just look at how the legal system works.
00:18:45.520 David goes on to say, quote, whenever I have used Dr. Johnson's criterion to argue for the reality
00:18:50.960 of something, one attribute in particular has always been relevant, namely complexity. We prefer
00:18:56.480 simpler explanations to more complex ones. And we prefer explanations that are capable of
00:19:01.280 accounting for detail and complexity to explanations that can account only for simple aspects of
00:19:06.880 phenomena. Dr. Johnson's criterion tells us to regard as real, those complex entities which,
00:19:13.280 if we did not regard them as real, would complicate our explanations. For instance, we must regard
00:19:18.880 the planets as real because if we did not, we should be forced into complicated explanations
00:19:23.600 of a cosmic planetarium, or of altered laws of physics, or of angels, or of whatever else would
00:19:29.200 under that assumption, be giving us the illusion that there are planets out there in space. Thus,
00:19:34.960 the observed complexity in the structural behavior of an entity is part of the evidence that
00:19:40.400 that entity is real, but it is not sufficient evidence. We did not, for example, deem our
00:19:45.200 reflections in a mirror to be real people. Of course, illusions themselves are real physical
00:19:49.760 processes, but the illusory entities they show us need not be considered real because they
00:19:54.720 derive their complexity from somewhere else. They are not autonomously complex. Why do we accept
00:20:00.080 the mirror theory of reflections, but reject the planetarium theory of the solar system?
00:20:04.880 It is because, given a simple explanation of the action of mirrors, we can understand that nothing,
00:20:09.760 of what we see in them genuinely lies behind them. No further explanation is needed because
00:20:15.280 the reflections, though, complex are not autonomous. Their complexity is merely borrowed
00:20:20.480 from our side of the mirror. That is not so for planets. The theory that the cosmic planetarium is
00:20:26.080 real, and that nothing lies beyond it, only makes the problem worse. For if we accepted it,
00:20:30.720 then instead of asking only how the solar system works, we should first have to ask how the
00:20:35.520 planetarium works. And then how the solar system it is displaying works. We could not avoid the
00:20:40.640 latter question, and it is effectively a repetition of what we were trying to answer in the first
00:20:44.880 place. Now we can rephrase Dr Johnson's criterion thus, if, according to the simplest explanation,
00:20:52.080 an entity is complex and autonomous, then that entity is real. Computational complexity theory
00:20:57.840 is the branch of computer science that is concerned with what resources, such as time,
00:21:02.880 memory capacity, or energy, are required to perform given classes of computations. The complexity
00:21:08.880 of a piece of information is defined in terms of the computational resources, such as the length
00:21:14.560 of the program, the number of computational steps or the amount of memory that a computer
00:21:19.040 would need if it was to reproduce that piece of information. Several different definitions of
00:21:24.160 complexity are in use, each with its own domain of applicability. The exact definitions need
00:21:28.800 not concern us here, but they are all based on the idea that a complex process is one that
00:21:34.240 in effect presents us with the results of a substantial computation. The sense in which the
00:21:38.880 motion of planets presents us with the results of a substantial computation is well illustrated by
00:21:44.400 a planetarium. Consider a planetarium controlled by a computer which calculates the exact
00:21:48.880 image that the projectors should display to represent the night sky. To do this authentically,
00:21:53.200 the computer has to use the formula provided by astronomical theories. In fact, the computation
00:21:57.920 is identical to the one that it would perform if it were calculating predictions of where an
00:22:03.200 observatory should point its telescopes to see real planets and stars. What we mean by saying
00:22:10.080 that the appearance of the planetarium is as complex as that of the night sky depicts is that
00:22:15.760 those two computations, one describing the night sky, the other describing the planetarium,
00:22:21.200 are largely identical. So we can re-express Dr Johnson's criterion again in terms of hypothetical
00:22:28.240 computations. Quote, if a substantial amount of computation would be required to give us the illusion
00:22:35.200 that a certain entity is real, then that entity is real. If Dr Johnson's leg invariably
00:22:41.520 rebounded when he extended it, then the source of his illusions, God, a virtual reality machine
00:22:47.360 or whatever, would need to perform only a single computation to determine when to give him the rebounding
00:22:52.800 sensation, something like if leg is extended, then rebound. But to reproduce what Dr Johnson
00:22:58.880 experienced in a realistic experiment, it would be necessary to take into account where the rock is
00:23:04.320 and where the Dr Johnson's foot is going to hit or miss it and how heavy, how hard and how
00:23:08.800 firmly lodged it is and whether anyone else has just kicked it out of the way and so on, a vast
00:23:13.600 computation, pausing their my reflection. So yes, this is the point. If you're trying to assert
00:23:21.200 that what external reality appears to be isn't actually real, but rather it's an illusion,
00:23:26.800 it's a dream, it's a deception by a demon or a god or something like that, then what you're
00:23:31.440 saying is that those objects in the illusion, the dream rocks, the dream people, the dream planets
00:23:37.760 and so on and so forth are acting in such a way that is so complex that if you were to get a
00:23:43.200 computer to actually compute what is required in order to make the illusion as real, as realism
00:23:49.360 would otherwise seem, means that you have to compute precisely the laws of physics as they are
00:23:55.840 under realism. Basically, if you're trying to create the illusion of a rock, you need to simulate a
00:24:00.800 rock and the higher the fatality of the simulation of that rock, the more computation is required
00:24:06.880 and clearly if you've got an illusion that has the fidelity of realism, then you're going to have
00:24:12.880 to do a simulation that is of such high resolution that you may as well just that you may as well
00:24:19.440 just fall back on realism realism is just all of that simulation without the needless extra assumption
00:24:26.880 that it's all a simulation. But we might very well consider where is this really an issue,
00:24:32.800 apart from in the hallowed halls of academia in the ivory tower debating about whether or not
00:24:38.000 we're all living in a simulation or it's all a dream, does this really have any practical
00:24:42.240 significance? Is it really a scientific question? Well yes, of course it is, this is one of the
00:24:47.600 motivations for the fabric of reality is in trying to persuade people that there is a realistic way
00:24:53.680 of looking at quantum theory. So yes, because this has many antecedents, okay the classic one is of
00:25:00.240 course Galileo, Galileo, trying to convince the church that it wasn't just that we appeared
00:25:05.760 to live in a universe where the sun was at the center and the earth was orbiting the sun,
00:25:10.240 but rather those appearances were reality. The explanation of the sun being at the center and the
00:25:16.720 earth going around the sun and the other planets going around the sun wasn't merely a convenient
00:25:20.640 mathematical device for making predictions, it was reality. And so we come forward to today where
00:25:27.200 people deny the realistic conception of quantum theory, they deny the richness of what reality
00:25:33.840 contains, but we need that richness, that complexity, that computational complexity in order to be
00:25:39.520 able to make the accurate predictions that we do make. Nowhere is this more clear than in the case
00:25:44.400 of quantum theory, as David goes on to say in this very chapter, quote, physicists, trying to cling
00:25:51.600 to a single universe worldview, sometimes try to explain quantum interference phenomena as follows,
00:25:57.600 no shadow photons exist, they say, or in other words no multiverse exists, and what carries
00:26:02.800 the effect of the distant slits to the photon we see is nothing, some sort of action at a distance,
00:26:09.520 as in Newton's law of gravity, simply makes photons change course when a distance that is opened,
00:26:16.160 but there is nothing simple about the supposed action at a distance. The appropriate physical law
00:26:22.080 would have to say that a photon is affected by distant objects exactly as if something
00:26:28.160 were passing through the distant gaps and bouncing off the distant mirrors, so as to intercept
00:26:33.600 that photon at the right time and place, calculating how a photon reacts to these different
00:26:39.200 objects would require the same computational effort as working out the history of large numbers
00:26:44.880 of shadow photons, the computation would have to work its way through a story of what each
00:26:50.320 shadow photon does, it bounces off this, is stopped by that, and so on, therefore,
00:26:55.840 just as with Dr. Johnson's rock, and just as with Galileo's planets, a story that is in effect
00:27:01.680 about shadow photons necessarily appears in any explanation of the observed effects, the
00:27:07.200 irreducible complexity of that story makes it philosophically untenable to deny that the object
00:27:13.600 exists, end quote, this is just my reflection here, another way of putting this is that
00:27:18.960 well, when you look at the shredding away the equation, which is a description of the position,
00:27:25.120 for example, it doesn't have to be the position, it could be any of the other quantum properties
00:27:30.480 that a particle or a system happens to have, it could be the velocities of these particles,
00:27:35.040 but let's say in a simple case we're just talking about, I don't know, the position of a single
00:27:40.080 electron, then what you have at some time t is a plot of all the positions that, in theory,
00:27:47.440 actually in reality, but in theory, the electron is occupying, and you need to have all of these
00:27:54.240 positions in order to be able to make some claim about how this electron is going to behave
00:28:01.120 in the future, so what positions it could possibly occupy in the future at some future time t,
00:28:07.520 and so if you're going to make that prediction by calculating using the laws of quantum theory,
00:28:12.640 you have to know what all the positions are now, and if all those positions come together now
00:28:17.520 in order to affect future positions and future velocities of the electron, then in what sense
00:28:23.680 aren't they real? Well, some people just deny that these are all real, and in fact, that all
00:28:27.920 the possible positions that the electron could have at some point in the future, well, they all
00:28:32.480 collapse, as we say, the collapse of the wave function happens upon measurement, and this is to deny
00:28:39.440 the reality of all those other positions, and yet those other positions were required in order to
00:28:44.720 make sensible claims about where the electron is now and where the electron might be found in the future.
00:28:51.280 So, this is the sense in which it is as computationally complex to either have a single
00:28:57.760 universe theory or a many universe's theory. The single universe's theory simply says that all the
00:29:03.520 entities are required to take account of when you're computing what it's going to happen from
00:29:09.520 one moment to the next, using the laws of quantum theory. All those entities are not real, the only
00:29:13.680 ones that are real are the ones that you observe, so there's some special place for the observer,
00:29:18.080 there's some special physics for the observer, and this is what the multiverse vision of quantum
00:29:23.680 theory denies. It says there is no special dip dispensation, there is no special theory of physics
00:29:28.800 for observers, there is one universal physics for everything, observers and non-observers,
00:29:34.720 and hence it's all real, all the things required in the computation, everything that makes these
00:29:39.360 situations computationally complex are real. But still, some people deny the reality of the things
00:29:46.400 that we cannot see, which, as we've said in this podcast, as David says in both of his books,
00:29:50.960 over and over again, is a strange way of envisioning what science is, science is the scene in terms
00:29:58.560 of the unseen. As David goes on to say right now, quote, the physicist David Bonne,
00:30:04.640 constructed a theory with predictions identical to those of quantum theory, in which a sort of
00:30:09.360 wave accompanies every photon, washes over the entire barrier, passes through the slits,
00:30:14.880 and interferes with the photon that we see. Bonne's theory is often presented as a single
00:30:19.760 universe variant of quantum theory, but according to Dr Johnson's criterion, that is a mistake.
00:30:25.360 Working out what bones invisible wave will do requires the same computations as working out
00:30:30.560 what trillions of shadow photons will do. Some parts of the wave describe us, the observers
00:30:34.960 detecting and reacting to photons, other parts of the wave describe other versions of us,
00:30:39.600 reacting to photons in different positions. Bonne's modest nomenclature,
00:30:43.440 referring to most reality as a wave, does not change the fact that in his theory,
00:30:49.200 reality consists of large sets of complex entities, each of which can perceive other entities
00:30:54.800 in its own set, but can only indirectly perceive entities in other sets. These sets of entities
00:31:00.800 are, in other words, parallel universes, pausing their myreflection. Yes, so Bonne and wave
00:31:06.000 mechanics, this idea of David Bonne, that there is this indivisible wave that passes through
00:31:11.600 the slits, for example, that it is accompanying any particle that we see has an accompanying wave
00:31:17.920 associated with it. Well, this wave is just the counterparts in the other universes of the particle
00:31:23.760 that we see, and as David has said in other contexts, this is nothing but the multiverse
00:31:28.640 in heavy disguise, not even that heavy disguise, really, after all, if you were to have a god's
00:31:34.000 eye view of the multiverse, and if you were to see what happens during a interference experiment,
00:31:40.240 such as firing, I suppose, at one electron at a double slit, then what you would see is something
00:31:46.640 that looks like a wave, but that's just because the stupendously large amount of accompanying
00:31:51.920 electrons in other universes, there's so many of them that they appear to move, or when you take
00:31:57.600 them all together, the entire ensemble of them, the entire set of them, or class of them,
00:32:01.440 or how you want to describe them, appears to move kind of like a wave, it would kind of look
00:32:05.520 like a wave in higher dimensional space, it is a wave, and if you were to just glance at that
00:32:10.160 wave, you might very well say, well that's a wave, but then if you ask the question, what is
00:32:14.000 that wave made out of? And you look closely at higher resolution, you would see that the wave
00:32:19.760 that appears to be there is actually made up of lots and lots of particles, it's made up of
00:32:25.280 lots and lots of electrons that are accompanying the electron that any observer in any
00:32:29.120 particularly universe would observe as only being one electron. Let's continue, and David says,
00:32:34.240 quote, I have described Galileo's new conception of our relationship with external reality
00:32:39.680 as a great methodological discovery, it gave us a new reliable form of reasoning involving
00:32:45.200 observational evidence, that is indeed one aspect of his discovery, scientific reasoning is
00:32:50.640 reliable, not in the sense that it certifies that any particular theory will survive unchanged,
00:32:56.960 even until tomorrow, but in the sense that we are right to rely on it, for we are right
00:33:01.360 to seek solutions to problems rather than sources of ultimate justification. Observational evidence
00:33:07.680 is indeed evident, not in the sense that any theory can be deduced, induced, or in any other way
00:33:14.240 inferred from it, but in the sense that it can constitute a genuine reason for preferring one theory
00:33:20.400 to another, pausing there just my reflection on that. So how can observational evidence,
00:33:25.680 cause us to prefer one theory over another? Well simply by the fact that observational evidence
00:33:30.800 tends to refute all other theories except for one. Ideally this is what happens in science,
00:33:36.560 we end up only with one theory being able to explain the observational evidence. So all of its
00:33:41.600 rivals are no longer preferred, and this is what this is the sense in which we say that it allows us
00:33:47.520 to prefer one theory to another or one theory to all the other rivals. The observational evidence
00:33:53.280 simply rules out all the other rivals can only be explained by one theory, one explanation that we
00:33:59.440 have. To fall back on the most classic of all the examples that I use, Edington's experiment,
00:34:05.280 where starlight appears to be in one place rather than another, that one place that the starlight
00:34:09.760 does appear during a solar eclipse is predicted by general relativity, but none of the other rivals.
00:34:15.680 No other rival to general relativity can make that prediction in the way that general relativity
00:34:20.240 does, and so therefore we prefer general relativity over those other theories. Let's continue.
00:34:26.000 David says quote, but there is another side to Galileo's discovery which is
00:34:30.320 much less often appreciated. The reliability of scientific reasoning is not just an attribute of us,
00:34:36.560 of our knowledge and our relationship with reality, it is also a new fact about physical reality
00:34:41.760 itself, a fact which Galileo expressed in the phrase, the book of nature is written in mathematical
00:34:47.360 symbols. As I have said, it is impossible, literally, to read any shred of a theory in nature,
00:34:53.440 that is the inductivist mistake. But what is genuinely out there is evidence.
00:34:58.320 Or more precisely, a reality that will respond with evidence if we interact appropriately with it,
00:35:03.920 given a shred of a theory, or rather shreds of several rival theories, the evidence is available
00:35:09.280 out there, to enable us to distinguish between them, anyone can search for it, find it,
00:35:14.320 and improve upon it if they take the trouble that are not need authorization or initiation
00:35:19.680 or holy texts. They need only be looking in the right way, with fertile problems and promising
00:35:25.520 theories in mind. This open accessibility not only of evidence but of the whole mechanism of
00:35:31.200 knowledge acquisition is a key attribute of Galileo's conception of reality. Galileo may have
00:35:37.200 thought this self-evident, but it is not. It is a substantive assertion about what physical
00:35:42.160 reality is like. Logically, reality need not have had this science-friendly property,
00:35:48.320 but it does. And in abundance, Galileo's universe is saturated with evidence.
00:35:53.280 Copernicus had assembled evidence for his heliocentric theory in Poland.
00:35:57.360 Taiko Brahe had collected his evidence in Denmark and Kepler in Germany. And by pointing his
00:36:02.800 telescope at the skies over Italy, Galileo gained greater access to the same evidence,
00:36:07.840 every part of the Earth's surface on every clear night, for billions of years,
00:36:12.160 has been deluged with evidence about the facts and laws of astronomy. For many other
00:36:16.240 sciences, evidence has similarly been on display to be viewed more clearly in modern times by
00:36:21.040 microscopes and other instruments. Where evidence is not already physically present,
00:36:25.680 we can bring it into existence, with devices such as lasers and pierced barriers,
00:36:30.320 devices which it is open to anyone, anywhere at any time to build. And the evidence will be the
00:36:36.640 same regardless of who reveals it. The more fundamental a theory is, the more readily available
00:36:42.400 is the evidence that bears upon it to those who know how to look. Not just on Earth, but throughout
00:36:48.000 the multiverse, pausing their my reflection on this, isn't this a wonderfully positive,
00:36:53.120 optimistic way of envisioning how to do science. It's open to anyone anywhere to make these
00:37:00.560 profound discoveries as David Deutsch says elsewhere. The evidence, in order to win a Nobel
00:37:06.240 Prize, is here right now in this room either falling from the sky, in the form of light,
00:37:12.240 or around you in the atoms out of which the matter is made, for you to make the discovery.
00:37:17.760 That will lead to the next greatest breakthrough. That could lead to the Nobel Prize.
00:37:21.680 What he says there is, where evidence is not already physically present.
00:37:25.760 We can bring it into existence, with devices such as lasers and pierced barriers,
00:37:30.000 devices which it is open to anyone, anywhere, at any time, to build. Now, yes, building large
00:37:36.480 hydrodron colliders, and James Webb space telescopes. Yes, that's hard, that's expensive,
00:37:41.280 but in principle, in principle, it's possible. And as wealth increases for everyone,
00:37:46.800 this means it becomes more and more possible over time for people to have more and more
00:37:50.640 sophisticated equipment to make the scientific breakthroughs that are required to solve the
00:37:55.360 problems of the future. Everyone now, just about, carries around an extremely high
00:37:59.760 fidelity camera and a supercomputer in their pocket, which can do the kind of experimental work
00:38:06.000 that people before could only dream of. The fact that so few people used them in order to
00:38:11.280 actually do science, well, that's another issue. The fact is science is an even playing field.
00:38:18.000 It's as even as you like, and the cheap and readily available super technology that we have now,
00:38:23.600 in the form of smartphones and computers and that kind of thing, means that even if there is a
00:38:28.880 wealth inequality between people, that wealth inequality is actually decreasing over time. People
00:38:33.520 talk about the increase in equality, but that is usually only ever based on number of shares
00:38:40.000 and a company held by someone like Elon Musk, who happens to own one of the most profitable
00:38:44.800 companies or Jeff Bezos, who owns one of the most profitable companies, on the other hand,
00:38:49.600 inequality has never been more narrow. Many of us own phones identical to Elon Musk.
00:38:55.040 Elon Musk doesn't have a, well, Jeff Bezos doesn't have a, doesn't have better access to the day
00:39:00.560 to day technology than anyone else does. This did not used to be the case of course. You only
00:39:05.040 have to go back two or three decades and the top mobile phones that were available were well
00:39:10.400 out of the reach of the average person. Now, the top mobile phone, you know, as I'm recording this,
00:39:15.440 it's like the iPhone 13 pro or whatever. That is well within the budget of many, many people.
00:39:21.040 So if two for the top desktop computers and so on and so forth and all of this is to say
00:39:25.920 that the typical person has access to technology, which directed towards scientific discovery
00:39:33.040 could indeed make breakthroughs that people of the past could only have dreamed of and to
00:39:37.680 solve problems, even outstanding problems today. Routinely amateur astronomers make discoveries
00:39:42.720 of things like comets and even today exoplanets just by looking at published data on the internet
00:39:49.360 that's freely available and processing it. So the evidence is absolutely available to everyone
00:39:55.920 in order to make these discoveries to solve some of our most pressing problems. David goes on
00:40:00.800 to say, quote, thus physical reality is self similar on several levels. Among the stupendous complexities
00:40:08.800 of the universe and multiverse, some patterns are nevertheless endlessly repeated.
00:40:13.280 Earth and Jupiter are in many ways dramatically dissimilar planets, but they both move in ellipses
00:40:18.880 and they are both made of the same set of 100 or so chemical elements, albeit in different proportions
00:40:24.640 and so are their parallel universe counterparts. The evidence that so impressed Galileo and his
00:40:29.840 contemporaries also exists on other planets and in distant galaxies. The evidence being considered
00:40:35.440 at this moment by physicists and astronomers would also have been available a billion years ago
00:40:40.160 and will still be available a billion years hence. The very existence of general explanatory
00:40:45.120 theories implies that disparate objects and events are physically alike in some ways.
00:40:50.880 The light reaching us from distant galaxies is after all only light, but it looks to us like galaxies.
00:40:57.200 Thus reality contains not only evidence but also the means such as our minds and our artifacts
00:41:02.400 of understanding it. There are mathematical symbols in physical reality, the fact that it is
00:41:07.360 we who put them there does not make them any less physical in those symbols, in our planetariums,
00:41:12.080 books, films and computer memories, and in our brains. There are images of physical reality at large,
00:41:18.080 images not just of the appearance of objects but of the structure of reality. There are laws
00:41:23.120 and explanations, reductive and emergent, there are descriptions and explanations of the big bang
00:41:27.920 and of sub-nuclear particles and processes. There are mathematical abstractions, fiction, art,
00:41:32.800 morality, shadow photons, parallel universes, to the extent that these symbols, images,
00:41:38.080 and theories are true, that is, they resemble inappropriate respects, the concrete or abstract
00:41:42.960 things they refer to, their existence gives reality a new sort of self-similarity, the self-similarity,
00:41:49.440 we call knowledge. And that there is the end of chapter 4 of the fabric of reality, criteria,
00:41:57.040 for reality. And I want to note here just at the end there that powerful way of ending echoes what
00:42:02.880 is said by David in one of his dead talks where he talks about this kind of self-similarity
00:42:09.600 when he talks about the quasar. The most important kind of self-similarity is the self-similarity of
00:42:15.200 what happens inside of our minds where we try to understand objects in our world, including things
00:42:21.360 like quasars. What happens over time, the special relationship we have with the laws of physics
00:42:26.640 means that there can be an object like a quasar with physics as violent and unusual as it's
00:42:32.560 going on in a quasar. And that physics, we can come to understand. And so we can come to build
00:42:38.560 not merely, as David says, a visual representation of what the quasar looks like in our minds,
00:42:44.160 so we can see it in our minds eye. But also, we can have mathematical relationships,
00:42:49.680 we can come to understand the laws, the physical laws expressed in mathematical relationships,
00:42:54.640 and expressed in natural language in our minds as well. And over time, our explanation,
00:43:00.640 our model of that quasar comes to represent the real quasar, existing out there in physical reality
00:43:08.560 with greater and greater fidelity over time. The two structures, the model that's going on inside
00:43:13.600 of our minds, and the physical thing out there, billions of light years away, come to resemble
00:43:18.880 one another more and more accurately over time. This is self-similarity. This is the most important
00:43:24.160 kind of self-similarity that we know of, because it implies everything that we've been talking
00:43:28.960 about here, it implies realism, it implies that this explanation, this objective explanation that
00:43:34.080 is being built over time, error corrected over time, in our minds, conjectured over time in our
00:43:39.440 minds and error corrected, is coming to more accurately represent the reality, the physical
00:43:45.040 reality that's out there. And this final paragraph also, it is a defense of realism. It's also,
00:43:51.920 I would say, an improvement on pop-up. So let's go to that now. Let's have a look at what
00:43:56.960 Popper actually said in objective knowledge about common sense and realism, just briefly,
00:44:02.400 and I'm looking at page 37, if anyone wants to read along this as page 37 of objective knowledge,
00:44:07.840 he says, realism is essential to common sense, common sense or enlightened common sense,
00:44:13.600 distinguishes between appearance and reality. This might be illustrated by examples such as,
00:44:18.640 today the air is so clear that the mountains appear so much nearer than they really are,
00:44:22.640 or perhaps he appears to do it without effort, but he has confessed to me that the tension is
00:44:27.520 almost unbearable. But common sense also realizes that appearances, say a reflection in a looking
00:44:32.960 glass, have a sort of reality. In other words, that there can be a surface reality that is an
00:44:38.000 appearance and a depth reality. Moreover, there are many sorts of real things, and then
00:44:44.080 Popper goes on to list a whole bunch of real things. So I'll skip over that and we'll go to
00:44:49.440 Popper's arguments for realism that he comes to. He says, quote from Popper. My thesis is that
00:44:57.120 realism is neither demonstrable nor refutable. Realism, like anything else outside logic and
00:45:03.120 finite arithmetic, is not demonstrable. But while empirical scientific theories are
00:45:08.240 refutable, realism is not even refutable. Now, I would say he and a here is me translating
00:45:14.640 Popper and I could be getting this wrong. When he uses the word refutation here, what he's talking
00:45:19.120 about is experimental force authentication. Of course, we can refute realism or we can refute
00:45:26.800 any other philosophical theory that we like by means of philosophical argument. Now, we'll fail
00:45:32.960 to do so in the case of realism. It doesn't mean we can't say, hey, that's wrong because
00:45:38.160 here's my argument that the simulation hypothesis is correct. So I'm refuting realism.
00:45:42.320 I'm not successful in my refutation, but I'm attempting to refute it. Or it could also mean
00:45:48.160 that Popper is saying that there's simply no way that any argument can possibly refute realism
00:45:53.920 or possibly show that realism is wrong. I don't think he would go that far. After all, we're
00:45:57.760 fallible. And so making a category claim like it's impossible to even show a flaw with realism
00:46:03.840 can't possibly be the case. Anyway, whatever the case, he goes on to say that realism not being
00:46:08.960 refutable shares this irrefutability with many philosophical or metaphysical theories, in particular,
00:46:14.560 also with idealism. Yes, so there we have it. So he's essentially, he must be saying there that
00:46:20.160 all of these metaphysical theories, idealism or whatever else, the simulation hypothesis,
00:46:24.480 are not experimentally testable or experimentally forceifiable. And he's identifying that with
00:46:30.560 refutability. It could be the case that he's simply wrong as well. And as David has pointed out
00:46:35.200 in the fabric of reality, well, we can refute idealism. How? Well, by talking about the sheer
00:46:41.680 amount of computation required in order to generate an idealistic conception of the world, if
00:46:47.040 you take seriously what idealism is, then you would need to have some means of computing where
00:46:51.920 all of the objects in your dream world happen to be. And that would amount to computing what's
00:46:57.200 really going on in the world. And so therefore we have realism. So there's all sorts of ways of
00:47:01.920 coming at this refutation of things that aren't realism. So that very well could be a simple
00:47:07.120 improvement on Popper, because he goes on straight away to say, but it is arguable. And the weight
00:47:12.480 of the arguments is overwhelmingly in its favor. Okay. So, so this is a poor phrasing, I would say
00:47:19.840 if Popper, the weight of the arguments. Okay. So we don't endorse this idea that we have weight
00:47:24.960 of arguments. Better to say so if he's just saying, a good explanation is what David would say
00:47:31.920 presumably, the way in which to really come at this is to say that we refute idealism because
00:47:38.640 it's a bad explanation rather than talking about weight of arguments. We can argue for realism
00:47:44.000 because it is the best explanation of our metaphysical ontology if we want to use the fancy words,
00:47:49.760 but that's the fact of the matter. Our best explanation, the most parsimonious way of viewing
00:47:54.960 our experience of the world is that it really exists. There's an external reality out there beyond
00:48:00.640 our dreaming, beyond our being inside of a simulation or anything else like that. Popper goes on
00:48:05.440 to say, quote, common sense is on the side of realism. There are, of course, even before day
00:48:09.840 cart, a few hints of doubt whether or not our ordinary world is perhaps just a dream, but even day
00:48:15.440 cart and lock were realists. A philosophical theory competing with realism did not seriously start
00:48:21.120 before Berkeley, Hume and Kant. Kant incidentally even provided a proof for realism, but it was not
00:48:27.440 a valid proof and I think it important that we should be clear why no valid proof of realism
00:48:32.800 can exist. End quote, quite right. We can't and we don't need to. The proof is not the most
00:48:38.800 important thing unless you are someone who subscribes to the hierarchy that David talks about
00:48:43.600 in the fabric of reality in the chapter I just read where mathematical proof, mathematics,
00:48:49.040 the certainty one supposedly gets with mathematics is the gold standard against which all other
00:48:54.560 claims to truth must be measured. And the only thing that sort of gets anywhere near that is
00:49:00.240 scientific confidence that we have these arguments where we collect the evidence and we become
00:49:05.120 highly confident in our scientific claims, whereas philosophy isn't a matter of taste. So we don't
00:49:10.160 need to worry about the fact there's no valid proof for realism. There's no scientific evidence
00:49:14.640 for realism. We have a robust explanation of realism, a philosophically rigorous argument that explains
00:49:23.440 why realism is correct. So what does Papa say about idealism? Well he says quote, in its simplest form,
00:49:29.520 idealism says the world which includes my present audience is just a dream. Now it is clear that
00:49:34.800 this theory, though you will know it is false, is not refutable. Whatever you, my audience,
00:49:39.600 may do to convince me of your reality talking to me or writing a letter or perhaps kicking me,
00:49:43.520 it cannot possibly assume the force of a refutation. For I would continue to say that I am
00:49:48.480 dreaming that you are talking to me or that I receive the letter or filter kick. One might say that
00:49:53.840 these answers are all in various ways, immunising strategies. That is so, and it is a strong
00:49:59.840 argument against idealism. But again, that it is a self immunising theory, does not refute it.
00:50:05.280 So we can see there that clearly what he means by refutation is experimental falsification,
00:50:10.480 rather than refutation by it being a bad explanation or rejecting it because it's a bad
00:50:17.120 explanation. And he continues quote, thus idealism is irrefutable. And this means of course that
00:50:22.960 realism is indomonstrable. But I am prepared to concede that realism is not only indomonstrable,
00:50:28.960 but like idealism irrefutable also, that no describeable event and no conceivable experience
00:50:35.920 can be taken as an effective refutation of realism. Thus there will be in this issue as in so many
00:50:42.720 no conclusive argument, but there are arguments in favour of realism or rather against idealism.
00:50:49.360 And now proper goes on to list his arguments against idealism or for realism if you like.
00:50:54.560 One, perhaps the strongest argument consists of a combination of two, a, that realism is part of
00:51:01.440 common sense, and b, that all the alleged arguments against it are not only philosophical in the
00:51:06.560 most derogatory sense of this term, but are at the same time based upon an uncritically
00:51:11.280 accepted part of common sense, that is to say upon that mistaken part of the common sense
00:51:15.920 theory of knowledge, which I have called the bucket theory of mind. And two, although science is
00:51:20.720 a bit out of fashion today with some people, for reasons which are regrettably far from negligible,
00:51:25.760 we should not ignore its relevance to realism despite the fact that there are scientists who
00:51:30.400 were not realists, such as Ernst Mark or in our own lifetime Eugene Wigner. Their arguments fall
00:51:36.480 very clearly in the class just characterising 1b, let us hear forget about Wigner's argument from
00:51:41.840 atomic physics, we can then assert that almost all, if not all, physical, chemical, or biological
00:51:47.680 theories imply realism, in the sense that if they are true, realism must also be true. This is one
00:51:53.680 of the reasons why some people speak of scientific realism, it is quite a good reason, because if it's
00:51:58.320 apparent lack of testability, I myself happen to prefer to call realism metaphysical rather than
00:52:04.320 scientific. However, one may look at this, there are excellent reasons for saying that what we
00:52:08.960 attempt in science is to describe, and so far as possible, explain reality. We do so with the help
00:52:15.440 of conjectural theories, that is, theories which we hope are true or near the truth, but which
00:52:20.480 we cannot establish a certain or even as probable in the sense of a probability calculus,
00:52:25.600 even though they are the best theories which we are able to produce and may therefore be called
00:52:31.040 probable as long as this term is kept free from any association with the calculus of probability,
00:52:36.080 there is a closely related and excellent sense in which we can speak of scientific realism.
00:52:41.280 The procedure we adopt may lead as long as it does not break down for example because of
00:52:45.840 anti-rational attitudes to success in the sense that our conjectural theories tend progressively
00:52:51.280 to come nearer to the truth that is, to true descriptions of certain facts or aspects of reality,
00:52:56.880 and then go pop it on to make some more remarks about realism, but I'm going to pick it up,
00:53:00.960 I'm going to skip that and pick it up where he says, quote, to me idealism appears absurd.
00:53:06.720 For it also implies something like this, that it is my mind which creates this beautiful world,
00:53:11.760 but I know I am not its creator, after all the famous remark beauty is in the eye of the beholder,
00:53:17.440 though perhaps not an utterly stupid remark, means no more than that there is a problem of the
00:53:22.800 appreciation of beauty. I know that the beauty of Rembrandt self-portrait is not in my eye,
00:53:28.400 nor that of Bach's passion in my ear. On the contrary, I can establish to my satisfaction
00:53:33.200 by opening and closing my eyes and ears that my eyes and ears are not good enough to take in
00:53:38.480 all the beauty that is there. Moreover, there are people who are better judges,
00:53:42.560 better able than I, to appreciate the beauty of pictures and music, denying realism,
00:53:47.360 amounts to megalomania, the most widespread occupational disease of the professional philosopher.
00:53:54.320 That's great, end quote. So there, Popper is actually getting out. He's hinting at what David
00:53:59.760 says, using different language, of course, that the inner workings of the mind of the supposed
00:54:06.800 idealists would have to be as complex as what realism actually is, okay, would contain all of
00:54:12.160 this complexity. And he goes on to say, quote, out of many other way, although inconclusive arguments,
00:54:17.280 I wish to mention only one. It is this, if realism is true, more especially something approaching
00:54:23.200 scientific realism than the reason for the impossibility of proving it is obvious. The reason is
00:54:28.560 that our subjective knowledge, even perceptual knowledge, consists of dispositions to act and is
00:54:34.320 thus a kind of tentative adaptation to reality and that we are its searches at best and at any rate
00:54:41.600 fallible. There is no guarantee against error. At the same time, the whole question of the truth
00:54:48.240 and falsity of our opinions and theories clearly becomes pointless if there is no reality,
00:54:53.680 only dreams or illusions. To sum up, I propose to accept realism as the only sensible hypothesis
00:54:59.760 and as a conjecture to which no sensible alternative has ever been offered. I do not wish to be
00:55:05.120 dogmatic about this issue any more than about any other, but I think I know all the epistemological
00:55:09.840 arguments. They are mainly subjectivists, which have been offered in favour of alternatives to realism,
00:55:15.280 such as positivism, idealism, phenomenalism, phenomenology and so on. And although I am not an
00:55:21.120 enemy of the discussion of isms in philosophy, I regard all the philosophical arguments which,
00:55:26.720 to my knowledge, have ever been offered in favour of my list of isms are clearly mistaken.
00:55:31.840 Most of them are the result of a mistaken quest for certainty or for secure foundations on which
00:55:37.200 to build and all of them are typical philosophers, mistakes and the worst sense of the term.
00:55:42.000 They are all derivatives of the mistaken, the common sense of the theory of knowledge,
00:55:45.840 which does not stand up to any serious criticism, pausing their my reflection. That is wonderful
00:55:50.800 there. That is a wonderful philosophical refutation of all of those isms he talks about and a
00:55:56.560 defence of realism. All of these alternatives, idealism, chief among them and its cousins,
00:56:02.800 what Popper is saying there is that the only reason, the only motivation that anyone has for putting
00:56:08.400 the forward in the first place is because they want a secure foundation. They are relying on the
00:56:12.640 justified true belief conception of knowledge. They do not believe in conjecture or knowledge
00:56:16.080 in the first place. They want to know, in the case of modern variants like the simulation hypothesis.
00:56:21.520 Why postulator? We will say that you can have some way of saying well this is absolutely
00:56:25.200 certainly the case. This is certainly what our ultimate reality consists of. Its simulations
00:56:30.560 inside of simulation, inside of simulations. Now I'm justified in my belief that realism,
00:56:36.320 naive realism is not the case, it's not true. But if you're a Papyrian, if you're a fallibleist,
00:56:43.040 then you just say well there's no way of being certain about any of this. But it's a good
00:56:47.600 working hypothesis, just to say that we know that realism is the case and we can come to know
00:56:52.800 that external physical reality that really exists better and better over time, never with certainty.
00:56:57.600 But it's a good way, it's a good place to start on the assumption that realism is true.
00:57:02.080 So I'll end it there for today and just to know that, just to notice that people have asked me,
00:57:07.520 I think in my ask me anything episodes where David has improved upon Popper and I gave a few
00:57:13.440 indications of where I thought David had improved on Popper. Here's another one, okay,
00:57:16.960 in this defense of realism. This defense of realism, I think the most parsimonious way of defending
00:57:23.200 realism is to say it's the best explanation. All these other ways of trying to come at the ultimate
00:57:28.160 metaphysical ontology, what really truly is the case when it comes to the experience we find ourselves
00:57:33.600 in. The reason why idealism fails to be the best explanation is because it ultimately is realism
00:57:40.240 with the additional philosophical assumption that we're just dreaming realism into existence.
00:57:45.600 And I think David has the best way of explaining what it means for something to exist
00:57:49.920 or what it means for something to be real in the beginning of infinity, where he says I think
00:57:53.680 is real or I think exists in so far as it appears in our best explanations of reality and not
00:57:59.280 otherwise. That's how we know, that's how we can conclude a thing exists. So that's the end of the
00:58:05.520 episode today. If you'd like to become a Patreon supporter, please feel free, you can search for that
00:58:10.960 on Google, okay, just search for Patreon, Topcast or Patreon, Brett Hall, but until next time, bye-bye.
