David Deutsch's "The Fabric of Reality" Chapter 5 “Virtual Reality”

00:00:00.000 Welcome to Topcast and to the next episode in my readings from and reflections upon
00:00:05.360 the fabric of reality. And today it's chapter five, virtual reality. And really this chapter
00:00:12.000 is like a mini exploration of the entire book itself. It's very synecticky if you know the term.
00:00:19.680 The idea that part of the whole can represent the whole. And what I continue to marvel at in this book
00:00:26.800 is it's prescience in a sense which is kind of silly. It's a silly thing to say because David of
00:00:32.320 course is the author. But it seems prescient in retrospect because it seems to predict so much of the
00:00:38.880 content of the beginning of infinity that absolutely has a standard everyone that has read it
00:00:44.960 ever since. But all that means really is that I just continue to be amazed how much I missed
00:00:50.960 the first time around with the fabric of reality. But again, I forgive myself. I was only
00:00:56.480 twenty years old at its publication and extremely busy at that time. And so it was a lot to
00:01:02.240 absorb. And today we're going to cover in this one chapter, computation and universality.
00:01:07.680 The nature of personhood to some extent and the centrality of explanations. The nature of
00:01:12.960 mathematics and the limits upon it imposed by physics and lots, lots more. All of those huge
00:01:19.200 themes that come up here on topcast because they feature so heavily in the work of David Deutschmore
00:01:25.360 broadly. So no long introduction today. Let's just get into some reading chapter five,
00:01:30.960 virtual reality and David writes. The theory of computation has traditionally been studied
00:01:35.680 almost entirely in the abstract as a topic in pure mathematics. This is to miss the point of it.
00:01:40.960 Computers are physical objects and computations are physical processes. What computers
00:01:45.520 cannot compute is determined by the laws of physics alone and not by pure mathematics.
00:01:51.680 One of the most important concepts of the theory of computation is universality. A universal
00:01:56.320 computer is usually defined as an abstract machine that can mimic the computations of any
00:02:01.600 under abstract machine in a certain well-defined class. However, the significance of
00:02:06.720 universality lies in the fact that universal computers are at least good approximations to them
00:02:12.400 can actually be built and can be used to compute not just each other's behaviour,
00:02:16.800 but the behaviour of interesting physical and abstract entities. The fact that this is possible
00:02:23.360 is part of the self-similarity of physical reality that I mentioned in the previous chapter.
00:02:29.040 The best known physical manifestation of universality is an area of technology that has been
00:02:34.080 muted for decades but is only now beginning to take off, namely virtual reality. Just
00:02:40.080 pausing their more reflection and of course I'm going to come back to this throughout the chapter.
00:02:44.480 But not to harp on about it but remember that this book was written in 1997. So now 25 years
00:02:49.920 later not only has virtual reality begun to take off it is routine to find it in all sorts of places
00:02:56.880 into society, not least people's homes as an entertainment device. I know I've got one, a PS4 VR
00:03:03.120 machine and the PS4 VR machine is one of the lower cost ones but it's still fantastic for a whole
00:03:08.480 bunch of things and I will come back to process of that. Let's go back to the book and David
00:03:12.320 Wright's quote. The term refers virtual reality to any situation in which a person is artificially
00:03:17.760 given the experience of being in a specified environment. For example a flight simulator, a machine
00:03:22.480 that gives pilots the experience of flying aircraft without having to leave the ground is a type
00:03:27.360 of virtual reality generator. Such a machine or more precisely the computer that controls it
00:03:32.240 can be programmed with the characteristics of a real or imaginary aircraft. The aircraft's environment
00:03:38.000 such as the weather and the layout of airports can also be specified in the program and quote
00:03:44.800 and just my reflection on that because from here David goes on for a few paragraphs talking about
00:03:49.840 the operation of a flight simulator which I won't like I say 25 years after he wrote this because
00:03:56.720 this chapter is referring to some specific technologies which at the time we're extremely new
00:04:01.440 but now people I think are far more familiar with them we don't need the detailed description. Like
00:04:08.000 I say personally I love my PS4 VR machine it's great there's a number of first-person shooter
00:04:13.760 games you can get with these virtual reality things. I've got this game called Farpoint it's
00:04:18.800 the name of this game where you're on an alien planet just filled with spiders and the spiders
00:04:23.600 can jump and a lot of them are massive. I wouldn't say it's realistic but it's realistic enough
00:04:28.720 it's very cool very scary and so you are you are totally immersed because visually you're totally
00:04:33.440 immersed and you've got their headphones in and so of course auditory you're totally immersed
00:04:38.080 but your other senses are not but it's enough it's enough to have just your hearing in your
00:04:42.080 side of course completely consumed by the VR machine to make you feel like you're really there
00:04:47.200 on this alien planet somewhere other shooting at spiders that are jumping at you and attacking you
00:04:51.920 and the VR of course is not only taking off it just continues to get better and better and the
00:04:56.160 only annoying thing at the moment is the weight of the headset the how cumbersome these things are in
00:05:02.320 any place even the wireless ones are still rather cumbersome and focusing at the goggles for me
00:05:08.000 has always been a bit of a pain but otherwise like I say it's fully immersive as far as
00:05:11.680 sight and hearing goes so I'm skipping all of this section where David is giving us an overview of
00:05:17.280 the functioning of flight simulators especially for people who at the time wouldn't have been
00:05:20.960 familiar with these things hardly at all so I'm going to pick it up where David is introducing a
00:05:26.480 piece of nomenclature for the purpose of this chapter and he says quite I shall use the term image
00:05:32.800 generator for any device such as a planetarium a high-fi system or a spice rack which can generate
00:05:39.200 specifiable sensory input for the user specified pictures sounds odors and so on all count as
00:05:46.800 images for example to generate the olfactory image i.e. the smell of vanilla one opens the vanilla
00:05:52.080 bottle from the spice rack to generate the auditory image i.e. the sound of Mozart's 20th piano
00:05:57.840 concerto one plays the corresponding compact disc on the high-fi system any image generator is a
00:06:03.840 rudimentary sort of virtual reality generator but the term virtual reality is usually reserved
00:06:08.400 for cases where there is both a wide coverage of the user sensory range and a substantial element
00:06:14.880 of interaction kicking back between the user and the simulated entities end quote okay so like I
00:06:21.520 say that's just a bit of nomenclature to be used in this chapter this image generator idea
00:06:25.600 and we'll need it in what to come okay so I'm skipping again a vast sway though the beginning of
00:06:31.440 this chapter I'm going to pick it up where David writes quote if Bishop Barkley or the inquisition
00:06:36.800 had known of virtual reality they would probably have seized upon it as the perfect illustration of
00:06:42.400 the deceitfulness of the senses backing up their arguments against scientific reasoning what
00:06:47.520 would happen if the pilot of the flight simulator tried to use Dr Johnson's test for reality
00:06:52.400 although the simulated aircraft and its surroundings do not really exist they do kick back at
00:06:57.200 the pilot just as if they would if they did exist the pilot can open the throttle and hear the
00:07:01.920 engines roar in response and feel their thrust through the seat and see them through the window
00:07:07.200 vibrating and blasting out hot gas in spite of the fact that there are no engines there at all
00:07:12.080 the pilots make experience the aircraft through a storm and hear the thunder and see the rain
00:07:16.960 driving against the windscreen though none of those things is there in reality what is outside
00:07:22.240 the cockpit in reality is just a computer some hydraulic jacks television screens and loud speakers
00:07:28.400 and a perfectly dry and stationary room does this invalidate Dr Johnson's refutation of solipsism
00:07:34.800 no his conversation with Boswell could just as well have taken place inside a flight simulator
00:07:41.520 or if you did thus he might have said opening a throttle and feeling simulated engine kick
00:07:45.920 there is no engine there what kicks back is ultimately a computer running a program that calculates
00:07:50.560 what an engine would do if it were kicked but those calculations which are external to Dr Johnson's
00:07:56.000 mind respond to the throttle in the same complex and autonomous way as the engine would therefore
00:08:01.920 they pass the test for reality and rightly so for in fact these calculations are physical processes
00:08:07.680 within the computer and the computer is an ordinary physical object no less than an engine and perfectly
00:08:12.560 real the fact that it is not a real engine is irrelevant to the argument against solipsism after all
00:08:18.560 not everything that is real has to be easy to identify end quote just to explain that a little
00:08:24.320 bit more hear the idea is that the external reality is real even if it's a virtual reality
00:08:31.600 that that virtual reality is not part of the person it's autonomous and outside of the person
00:08:37.040 have any experience remember the whole idea here if we go back to previous chapters where David
00:08:41.600 was talking about idealism the bishop Barkley referenced there these philosophers thought that
00:08:46.880 well you could have this situation where your dreaming reality into existence it's all ideas
00:08:51.840 and it's all coming from within you this ancient idea really so solipsism is the claim that only
00:08:58.640 you exist in the universe and that you are dreaming everything into reality now what is our philosophical
00:09:04.720 refutation against that it's that most of reality is acting in an autonomous way a way that you
00:09:10.720 cannot possibly predict or explain without going out and investigating your own mind what is
00:09:17.120 supposedly your own mind which it turns out has all of the richness of objective reality
00:09:22.640 an external reality beyond your mind so you're just adding realism the claim that there is an
00:09:28.560 external objective physical reality beyond your mind you're adding to that that simple statement
00:09:35.520 of realism the additional assumption but you're dreaming at all okay and so here what David is saying
00:09:41.920 is even if even if you were going to be given all of this you know you're sort of born into a
00:09:47.600 virtual reality machine or something like that well it would still not show that solipsism is real
00:09:53.200 it would still show that something was external to you namely the computer running all of this
00:09:58.320 I would say it's like the difference between the person having the experience and what is
00:10:03.840 generating the experience during a dream it is the case that the contents of the dream are produced
00:10:09.760 by the person having the experience and there might be subjective unpredictability there
00:10:15.600 but what won't happen is a rich experience of something you've never experienced before a rich
00:10:21.600 experience you will not dream of having the actual experience of walking down let's say a the main
00:10:26.800 street of Melbourne Australia if you have never done that before or seen it and so on sure you
00:10:31.840 may dream and experience of that but not the actual experience which will contain specifics
00:10:35.840 accurate specifics you can't just dream up what particular buildings are actually there what
00:10:41.280 shops and signs and side streets you will pass and so on what actually is the case in Melbourne
00:10:46.880 in the main street of Melbourne is actually the case and you can't just dream that into existence
00:10:51.040 unless you've already had it you might have a dream of an experience but it won't be an accurate
00:10:56.000 representation of the real reality of what's going on in the main street of Melbourne on the
00:11:00.720 other hand of course if you have had that experience and in particular if it's an experience you have
00:11:04.880 daily because of your commute to work every single day going up and down the main street of Melbourne
00:11:09.680 then it might be the case your dreams will contain accurate specifics a virtual reality generator
00:11:15.840 could give you such an experience even though you've never had it performed reality
00:11:19.760 because it is part of external reality the reality external to you okay so once again
00:11:25.760 I'm skipping a couple of pages and I shall pick it up where David writes quote
00:11:31.280 Virtual reality rendering might seem to fall into the same philosophical category as illusions
00:11:36.960 false trails and coincidences for these two are phenomena which seem to show us
00:11:42.400 something real but actually mislead us we have seen that the scientific worldview
00:11:47.440 can accommodate indeed expects the existence of highly misleading phenomena
00:11:52.640 it is par excellence the worldview that can accommodate both human fallibility
00:11:57.440 and external sources of error nevertheless misleading phenomena are basically unwelcome
00:12:03.280 end quote someone once described David Deutsch's writing as extremely knowledge dense you're
00:12:09.680 getting a lot of information packed into a small amount of words okay he's very efficient
00:12:15.040 on the words in order to convey such a deep ideas and here's here's an example of that
00:12:20.720 we've got their refutations of empiricism claims about human fallibility the the idea of
00:12:29.520 errors and correcting errors and not being able to of course experience things as they are so
00:12:33.840 let's just unpack this a little bit what does it mean that we have seen that the scientific
00:12:38.720 worldview can accommodate indeed expects the existence of highly misleading phenomena
00:12:42.560 well I would say this is a kind of refutation of empiricism empiricism remember is this
00:12:48.640 philosophical position that some scientists especially claimed hold that we get information about
00:12:55.280 reality via our senses seeing is believing in other words this is what empiricism amounts to
00:13:01.600 but as we've been at pains to explain here most of what we see out there experience with
00:13:07.440 our senses is highly misleading and our trope example that we go to all the time is looking up into
00:13:13.360 the sky at night and seeing what stars apparently are that's highly misleading it's
00:13:18.080 misleading to think that what the information you're getting from your senses there just your bare
00:13:22.640 senses is it all going to actually tell you what the true nature of a star is after all it
00:13:30.560 appears to us it seems to any human being that what the star is is a tiny dim prick of white light
00:13:38.400 cold and perhaps closer than they are you don't get a sense of just how far away stars are
00:13:44.080 most of the ones you can see in the night sky are going to be some tens or hundreds and perhaps
00:13:50.560 at absolute most thousands in the case of the very brightest ones light years away you don't get a
00:13:56.000 sense of what a light you're is by looking at any bright point of light in the sky at night
00:14:01.200 after all some of them are nowhere near as far away as that they're the planets and not even
00:14:05.600 stars at all and as for most of the stars being cold and dim no the exact opposite okay so we're
00:14:11.440 getting very misleading information from our senses when you take your finger and you rub it across
00:14:16.960 a smooth surface the desk in front of you the window plane beside you something like that you feel
00:14:23.040 continuity you feel matter as if it is not made up of particles your your senses your physical
00:14:29.440 sensation of touch is unable to discriminate any level between the atoms out of which that matter
00:14:36.960 is truly made so we are misled rather often by our senses but what decides to science error
00:14:43.600 corrects that despite the fact we are fallible as David mentions there are human fallibility
00:14:49.600 and not only are we fallible there's external sources of error as well there's you know
00:14:53.600 measuring devices can go wrong despite that the scientific world view accommodates all of this
00:14:59.360 it expects it and it accommodates all of this how by correcting errors in all of that sense
00:15:04.880 data we have we conjecture explanations and then what's the purpose what do we use the evidence
00:15:10.560 that the sense data that we're gathering we use that in order to discriminate to decide between
00:15:16.320 theories we've already guessed I'm skipping a little and David goes on to say quote we shall see
00:15:21.920 that the existence of virtual reality does not indicate that the human capacity to understand
00:15:26.560 the world is inherently limited but on the contrary that it is inherently unlimited end quote
00:15:34.320 pausing there and I think you can guess what I'm going to say wow it's one of those things that
00:15:39.200 it's one of those quotes there where you just have to say well well well there's the beginning
00:15:43.920 of infinity here in chapter five of the fabric of reality let's read it again because it's just
00:15:49.520 it's a perfect encapsulation of the one of the deepest themes of the beginning of infinity
00:15:54.800 even though it's not in the beginning of infinity we might as well say nothing indicates quote
00:15:59.760 that the human capacity to understand the world is inherently limited but on the contrary
00:16:06.080 that it is inherently unlimited end quote true we human beings are people and people are defined
00:16:14.960 by their capacity to create explanatory knowledge and that capacity to create explanatory
00:16:22.080 knowledge is universal it can be turned in any direction onto any problem about any phenomena
00:16:27.440 there is nothing that there is no phenomena for which we cannot generate an explanation
00:16:31.920 we are universally in our capacity to generate explanations because if someone puts forward
00:16:37.280 something that we say it is claimed not to be explicable then they would have to have an
00:16:41.920 explanation as to why that thing is not explicable but that would be a problem that would be
00:16:47.280 soluble but more importantly than that as David likes to say any claim that a particular
00:16:53.120 phenomena is inexplicable to human beings is nothing but an appeal to the supernatural it's just
00:16:58.720 going back to standard theistic supernatural mystical magical explanation sort of been with us
00:17:05.200 since the beginning of time you can't possibly understand the mind of God you are a pathetic human
00:17:10.480 you are like a cockroach compared to the alien intelligence out there the artificial general super
00:17:15.920 intelligence that is yet to come or god of monotheism in all these cases you can't understand the
00:17:22.160 ultimate nature of reality so anyone even with their scientific rationalist mindset who comes
00:17:27.680 to you to say there is something there that cannot be understood by human beings is doing the same
00:17:33.360 thing as the priest the rabbi the monk and so on and so forth it was saying some things are
00:17:39.360 just beyond the can of people to ever fully appreciate and understand and I think that's fine
00:17:46.560 allow them to believe that so long as they're not getting in the way of everyone else who's actually
00:17:49.840 trying to come to a rational realistic understanding of reality okay we have optimism here now
00:17:55.520 optimism says problems are soluble and the hard stuff we have to deal with is human beings the
00:18:01.040 things that cause suffering the evils in the world can be overcome because they're just a matter
00:18:06.080 of a lack of knowledge so please step aside people who think that certain problems are not soluble
00:18:11.120 who think that our capacity for understanding the world is inherently limited those people can
00:18:16.880 step aside and allow the rest of us go forward into understanding reality because we think it's
00:18:23.680 inherently unlimited and so there's no barriers before us let's keep going and David writes quote
00:18:29.280 it's no anomaly brought about by the accidental properties of human sense organs but is a
00:18:34.160 fundamental property of the multiverse at large and the fact that the multiverse has this property
00:18:39.440 what property this property that the universe is comprehensible that we are in it and we can
00:18:43.680 comprehend the universe far from being a minor embarrassment for realism and science is essential for
00:18:48.240 both it is the very property that makes science possible it is not something that we would rather do
00:18:53.360 without it is something that we literally could not do without these may seem rather lofty claims
00:18:59.760 to make on behalf of flight simulators and video games but it is the phenomenon of virtual reality
00:19:05.280 in general that occupies a central place in the scheme of things not any particular virtual reality
00:19:11.680 generator so I want to consider virtual reality in as general away as possible what if any
00:19:19.280 are its ultimate limits what sort of environment can in principle be artificially rendered
00:19:23.920 and with what accuracy by in principle I mean ignoring transient limitations of technology
00:19:29.840 but taking into account all limitations that may be imposed by the principles of logic and physics
00:19:35.760 the way I have defined it a virtual reality generator is a machine that gives the user
00:19:40.400 experiences of some real or imagined environment such as an aircraft which is or seems to be
00:19:46.320 outside the user's mind let me call those external experiences external experiences are to be
00:19:52.320 contrasted with internal experiences such as one's nervousness when making one's first solo landing
00:19:57.920 or one surprise at the sudden appearance of a thunderstorm out of a clear blue sky a virtual
00:20:03.040 reality generator indirectly causes the user to have internal experiences as well as external ones
00:20:09.040 but it cannot be programmed to render a specific internal experience for example a pilot who makes
00:20:14.000 roughly the same flight twice in the simulator will have roughly the same external experiences
00:20:19.280 on both occasions but on the second occasion will probably be less surprised when the thunderstorm appears
00:20:24.880 of course on the second occasion the pilot would probably also react differently to the appearance
00:20:29.760 of the thunderstorm and that would make the subsequent external experiences quite different too
00:20:33.520 but the point is that although one can program the machine to make a thunderstorm appear in the pilots
00:20:38.560 field of view whenever one likes one cannot program it to make the pilot think whatever one likes
00:20:44.960 in response end quote and here David goes on to consider virtual reality that intervenes in the
00:20:52.000 mind directly you know drugs are one such thing but they're sort of low resolution approximations
00:20:58.000 to what we would imagine could be done in the future with individual electrodes going into
00:21:03.760 individual neurons or perhaps getting right into the synapse and fiddling with the neurotransmit
00:21:09.200 is directly if you can do that with some level of precision without limit you know presumably an
00:21:15.360 interface of the future would be able to replicate simulate interfere with whatever you want to do
00:21:21.440 with the individual neurotransmiters with the chemicals themselves therefore you'd be able to
00:21:27.040 simulate literally any experience that a brain could possibly conjure for the mind of a person
00:21:34.880 when nowhere near there yet a glass of wine is obviously going to alter your experience of reality
00:21:42.000 but it is a very crude method in which to alter one's mood or change one's experience of
00:21:49.200 the sensations and the data that's coming into their brain and then interpreted by their mind
00:21:54.480 okay so I'm skipping a bit and picking it up where David writes another type of experience
00:22:00.400 which certainly cannot be artificially rendered as a logically impossible one
00:22:06.000 I have said that a flight simulator can create the experience of a physically impossible flight
00:22:11.360 through a mountain but nothing can create the experience of factorizing the number 181
00:22:17.440 because that is logically impossible 181 it's a prime number believing that one has factorized
00:22:23.680 181 it is a logically possible experience but an internal one and so also outside the scope of
00:22:30.480 virtual reality another logically impossible experiences unconsciousness for when one is unconscious
00:22:36.560 one is by definition not experiencing anything not experiencing anything is quite different from
00:22:41.920 experiencing a total lack of sensations sensory isolation which is of course a physically
00:22:47.680 possible environment having excluded logically impossible experiences and internal experiences
00:22:53.440 we are left with the vast class of logically possible external experiences
00:22:58.320 experiences of environments which are logically possible but may or may not be physically possible
00:23:05.440 something is physically possible if it is not forbidden by the laws of physics in this book I
00:23:09.840 shall assume that the laws of physics include an as yet unknown rule determining the initial
00:23:15.040 state or other supplementary data necessary to give in principle a complete description of the
00:23:19.760 multiverse otherwise these data would be a set of intrinsically inexplicable facts in that case
00:23:25.440 an environment is physically possible if and only if it actually exists somewhere in the multiverse
00:23:30.400 i.e. in some universe or universes something is physically impossible if it does not happen
00:23:36.080 anywhere in the multiverse pausing their my reflection and importantly my ruminations on this so
00:23:42.000 following the science of cannon count following constructive theory and following what we know
00:23:47.520 about quantum theory given the everretian so-called interpretation unitary quantum theory it's true
00:23:54.000 that anything that can possibly happen is going to happen somewhere in the multiverse but that does
00:23:58.400 not mean that all things that happen unnecessarily caused or represented in equal measure throughout
00:24:04.880 the multiverse as a silly example every single time the lottery a new country is run
00:24:10.640 and you buy a ticket there is a possible sequence of universes where you are the winner
00:24:15.440 week upon week upon week upon week because it's physically possible it's not ruled out by the laws
00:24:20.960 of quantum theory and so therefore it's going to happen somewhere but each time you win the lottery
00:24:26.880 the measure of universes where you subsequently continue to win get ever thinner and thinner
00:24:32.800 there is a smaller and smaller measure of universes where that happens you shouldn't expect it
00:24:36.480 to happen it may very well happens somewhere in physical reality in the multiverse but these
00:24:42.080 long chains of coincidences they are not expected to continue and some of those chains of
00:24:47.440 coincidences can't be said to be causal you go to my multiverse series on that but what we're
00:24:53.440 basically saying here is the classic Harry Potter universe where a bespectled boy somewhere
00:24:59.360 in the multiverse every time he holds a loft a stick is wand and says the magic words
00:25:05.360 abracadabra or whatever they say in Harry Potter a lightning bolt a spark of electricity shoots out
00:25:11.440 from the wand now that's not because he says the magic words and it may have nothing whatever to do
00:25:18.640 with either the bespectled boy or with the wooden stick that he's holding these are just chains
00:25:24.480 of coincidences it's not causal it's not that the boy is causing the magic wand to be magic
00:25:31.920 and to release lightning from the tip of the wand these are just coincidental things yet it
00:25:39.360 appears causal to everyone in that universe and so people in that universe might believe come to
00:25:44.080 think that the bespectled boy is in fact magical but also in every single one of these universes
00:25:50.400 it should be expected that the very next time he says the magic words that no spark does happen
00:25:54.720 in the overall majority of universes where he does try it fails but there is a sliver of
00:25:58.960 universes where it continues to happen okay all of that is fine the put the thing here is that
00:26:03.600 there's a difference between something being physically possible in the universe actually happening
00:26:08.720 and something occurring in our world our part of the multiverse if you like where it actually
00:26:14.800 forms a causal explanation of what's going on and that usually comes down to the creation of
00:26:20.320 knowledge somewhere in the multiverse human beings have figured out how to be effectively
00:26:26.640 immortal you know not die of sickness maybe they still die of accidents but they've cured all
00:26:31.520 illnesses now that part of the multiverse is going to continue to grow presumably the proportion of
00:26:37.760 universes will continue to increase because it's physically possible and it's in very important
00:26:42.480 knowledge useful information which will grow over time because knowledge by its very nature
00:26:48.480 is useful information that's very useful people want to solve the problem of why human beings
00:26:53.600 keep on getting ill sick and dying and if we can figure out how to solve this then so will our
00:27:00.080 counterparts and other universes and if they already have we will too eventually if there's no
00:27:05.280 physical law standing in the way of effective immortality then this is a possible thing that will grow
00:27:13.120 in terms of how much of the multiverse it begins to occupy as David has written these papers the
00:27:18.400 structure of the multiverse is determined by information flow and so essentially what happens
00:27:23.200 into the distant future is a result of the knowledge creation that people undertake in our universe
00:27:29.520 and in universes right beside ours so to speak and so in our part of the universe where we're
00:27:35.040 creating knowledge that knowledge is of course possible and in the case of immortality or any
00:27:39.760 other important issue that we would like to find the solution for we'd like to find immortality
00:27:44.880 would like to find fusion power how to do it here safely on earth perhaps even something more
00:27:50.080 efficient than fusion power who knows what if it's possible then we will find it and that will
00:27:55.200 propagate throughout the multiverse and become an increasingly more important causal reason why
00:28:00.080 other things happen in the multiverse as compared to that other sequence of possible things
00:28:05.040 the Harry Potter universe is where I just mentioned where it will become an increasingly
00:28:08.400 smaller proportion of the multiverse over time when magic appears to have worked but never
00:28:14.160 actually did work okay but knowledge creation actual knowledge creation is a cause of the way in which
00:28:19.920 the multiverse evolves over time because that's useful information that continues to remain
00:28:25.440 instantiated in the universe continues to get itself copied because it's solving a particular
00:28:30.240 problem so that's how that comes to bear all on this let's continue David Ryan I define the
00:28:37.040 repertoire of a virtual reality generator as the set of real or imaginary environments that the
00:28:42.480 generator can be programmed to give the user the experience of my question about the ultimate
00:28:47.680 limits of virtual reality can be stated like this what constraints if any to the laws of physics
00:28:53.440 impose on the repertoire of virtual reality generators and in this section David goes on to consider
00:28:59.200 the resolution the the the limit of precision of senses now these days as he mentions and I'm
00:29:07.760 looking to read this part audio equipment speakers high-fidelity speakers and stuff it routinely
00:29:14.800 replicate precisely the sounds of reality you know I've got cats I play my cats because they
00:29:20.480 are entertained by it these sounds and images of birds on a screen now the sounds even to me
00:29:25.280 are completely indistinguishable from the real sounds that birds make so they are perfectly replicating
00:29:31.760 reality to me if I'm immersed in the sound escape of artificial bird sounds it may as well be
00:29:38.080 real bird sounds repeat for just about anything else I mean my is unable to distinguish at this
00:29:44.400 point between reality and the audible reproduction now there is a difference I would say
00:29:50.000 with music sometimes just because who knows what I I'm not a musician I can't explain this in
00:29:56.000 technical terms but certainly if you're at a concert there is a different experience and the sound
00:30:00.880 there is different to what I recorded concert is and I think they've got that quite right here
00:30:05.520 for reasons maybe listeners can tell me with screens with the visual stuff we're just about
00:30:09.840 there aren't we it's just about the case that a 4k or 8k 16k I think we're getting to high
00:30:18.400 resolution screen as of 2022 that's going to date as someone's going to be listening to this
00:30:22.560 in 2024 2026 and say we've got much better screens now anyway those screens are going to be
00:30:28.320 as high resolution as a window you're going to be able to look at the screen to be unable to tell
00:30:33.040 the difference between the screen and actual reality so with airwood sound with airwood vision
00:30:39.520 what about other stuff one of the really interesting ones neither
00:30:43.360 sight nor sound is smell and one of the pioneers of perhaps the pioneer of virtual reality as
00:30:50.720 we experience it now in games and so forth connected up to our computers he's
00:30:55.760 Jerome Lenny here who I've mentioned before in the podcast great iconoclastic thinker
00:31:00.720 another person by the way who apparently didn't complete high school I don't think
00:31:05.520 and not much university either but has contributed to many different fields
00:31:11.600 to mathematics to physics of course to technology now he wrote a book which I recommend to
00:31:17.520 everyone you are not a gadget wonderful book again about the deep mystery of what it is to be a
00:31:22.560 human being I've often said that Jerome Lenny here is my favorite optimistic pessimist
00:31:28.560 he's a bit of a pessimist about various matters but somehow comes around to this positive
00:31:35.120 wonderfully positive vision of human beings and even a positive vision of economics which is
00:31:41.280 rare today most of the people are tending the collectivist direction he tends more into the free
00:31:48.400 trade-free markets direction but there's still this sort of pessimism about technology now
00:31:54.960 maybe he's right to a certain extent about that he's not a great fan of social media that's
00:31:59.600 taking me far feel of what I wanted to say back in his first book you are not a gadget he
00:32:04.640 writes about this question about how to have smell in virtual reality can we have smell in the
00:32:11.120 same way that we have virtual reality sound and virtual reality vision what would goggles with
00:32:17.680 that stimulate the old factory system be like let me just read a section from you are not a gadget
00:32:22.640 page 184 if you happen to have the book and he writes so Jerome writes quote for 20 years or so
00:32:28.960 I gave a lecture introducing the fundamentals of virtual reality I'd review the basics of vision
00:32:33.840 and hearing as well as of touch and taste at the end the questions would begin in one of the
00:32:38.560 first ones was usually about smell will we have smells in virtual reality anytime soon maybe
00:32:45.040 but probably just a few odors are fundamentally different from images or sounds the latter can
00:32:50.880 be broken down into primary components that are relatively straightforward for computers and the
00:32:55.680 brain to process the visible colors are merely words for different wavelengths of light every sound
00:33:02.800 wave is actually composed of numerous sine waves each of which can be easily described mathematically
00:33:09.440 each one is like a particular size of bump in the corduroy roads of my childhood in other words
00:33:15.840 both colors and sounds can be described with just a few numbers a wide spectrum of colors
00:33:21.600 and turns is described by the interpolations between those numbers the human retina need be
00:33:27.440 sensitive to only a few wavelength or colors in order for our brains to process all the intermediate
00:33:32.080 ones computer graphics work similarly a screen of pixels each capable of reproducing red green or blue
00:33:38.560 can produce approximately all the colors that the human eye can see a music synthesizer
00:33:43.600 can be thought of as generating a lot of sine waves then layering them to create an array of sounds
00:33:49.200 odors are completely different as is the brain's method of sensing them deep in the nasal passage
00:33:55.120 shrouded by a mucus membrane sits a patch of tissue the olfactory epithelium
00:34:00.640 studded with neurons that detect chemicals each of these neurons has cup shaped proteins called
00:34:07.200 olfactory receptors when a particular molecule happens to fall into a matching receptor a neural
00:34:13.520 signal is triggered that is transmitted to the brain as an odor a molecule too large to fit into
00:34:18.720 one of the receptors has no odor the number of distinct odors is limited only by the number
00:34:23.840 of olfactory receptors capable of interacting with them Linda Bach of the Fred Hutchinson cancer
00:34:28.640 research center and Richard Axel of Columbia University winners of the 2004 Nobel Prize in Physiology
00:34:34.480 or Medicine have found that the human nose contains about 1000 different types of olfactory neurons
00:34:40.640 each type able to detect a particular set of chemicals this adds up to a profound difference
00:34:45.760 in the underlying structure of the senses a difference that gives rise to compelling questions about
00:34:50.800 the way we think and perhaps even about the origins of language there is no way to interpolate
00:34:56.240 between two smell molecules true odors can be mixed together to form millions of sense
00:35:02.080 but the world smells can't be broken down into just a few numbers on a gradient there is no
00:35:08.160 smell pixel think of it this way colors and sounds can be measured with rulers but odors must be
00:35:14.880 looked up in a dictionary that's a shame from the point of view of a virtual reality technologist
00:35:20.160 there are thousands of fundamental odors far more than the handful of primary colors perhaps someday
00:35:25.200 we will be able to wire up a person's brain in order to create the illusion of smell
00:35:29.680 but it would take a lot of wires to address all those entries in the mental smell dictionary
00:35:34.800 then again the brain must have some way of organizing all those odors maybe at some level
00:35:39.760 smells do fit into a pattern maybe there's a smell pixel after all okay end quote and then
00:35:45.840 Jaron goes on writing in this vein talking more about smell but that's very interesting isn't it
00:35:50.400 so fundamentally of a different kind so while you have wavelengths effectively for light and for
00:35:57.040 sound no such wavelength exists for smell instead as he says there it's a dictionary that you have
00:36:03.520 to look up particular things but David's not so much talking about that kind of limitation as
00:36:08.960 Jaron admits there and as David agrees if you could just get into the individual neurons
00:36:13.360 problem solved say problem solved of course in principle it's physically possible in practice
00:36:18.800 at the moment we don't have much of a clue about how to do this at all
00:36:21.920 and David actually writes in the very next section on this I'll just read the section that David
00:36:26.720 writes about this after he explains how virtual reality with vision and hearing would work he says
00:36:31.360 but what about the other senses quote is it obvious that it is physically possible to build a
00:36:36.560 general purpose chemical factory that can produce any specified combination of millions of different
00:36:42.240 odouriferous chemicals and a moment's notice or machine which inserted into a gormon's mouth can
00:36:47.840 assume the taste and texture of any possible dish to say nothing of creating a hunger and thirst that
00:36:51.920 proceed the meal and the physical satisfaction that follows it end quote so yes we've got difficulties
00:36:57.680 here with these other kinds of senses now again those practical difficulties pose no barrier to
00:37:04.000 what is physically possible and if you're watching this on YouTube I'm putting up the slide of the
00:37:11.200 image that appears in the book and it's a table of tag table 5.1 a classification of
00:37:17.280 experiences with examples of each virtual reality is concerned with the generation of
00:37:22.080 logically possible external experiences which are only in the top left region of the table
00:37:28.720 so for people listening we've got this table here of both external and internal experiences
00:37:34.560 and the logically possible experiences and logically impossible experiences so the ones that are
00:37:38.320 ruled out that no virtual reality generator can possibly generate to produce would be the experience
00:37:45.600 of factorizing a prime number that's an external experience which is logically impossible
00:37:50.000 and unconsciousness would be an internal experience which is logically impossible so it's
00:37:55.200 logically possible to be proud of one's piloting abilities but that's not something that a
00:38:00.720 virtual reality generator could do because the virtual reality generator we're talking about
00:38:04.720 isn't actually going directly into your mind to fiddle with your capacity to have a particular
00:38:11.440 thought or a particular idea so all of it of what a virtual reality generator is limited to
00:38:17.840 things that are external and physically possible and physically impossible as well so for example
00:38:23.440 piloting an aircraft is physically possible to an external experience but also piloting an
00:38:28.320 aircraft such that it flies faster than a bit of light as also something a virtual reality generator
00:38:32.960 could do physically impossible but it could give you that experience or at least represent that
00:38:38.320 experience David's about to explain a little bit more on that point now the before we get there
00:38:42.800 the next part is about some of the practical difficulties not merely difficulties perhaps
00:38:47.520 impossibilities of generating certain experiences or sensations one of which is to do with
00:38:54.560 gravity now now weightlessness is one such they can fiddle with someone's experience of
00:39:00.960 gravity in certain ways I know I had this back when I was a child and I went to Disneyland for
00:39:07.120 I think the only the second time they had a star wars ride and you went on this ride and of course
00:39:12.240 it was a virtual one of the early forms of virtual reality and you and the other people in the ride
00:39:17.760 all you were doing was staring at a screen and on the screen in front of you and you were also
00:39:21.760 listening to the sounds on the screen in front of you was was where you were going on the ride now
00:39:25.600 if it wanted to give you the experience of accelerating then of course the simulator thing just
00:39:30.800 like a flight simulator used hydraulics to pitch the entire thing upwards and if it wanted to give
00:39:36.400 you the experience of quickly decelerating then it pitch the thing downwards towards the ground
00:39:41.040 and this takes advantage of something called the equivalence principle now the equivalence principle
00:39:45.040 comes from general relativity it's an important idea where if you're listening to this on planet
00:39:50.720 earth and you're sitting down then the force of gravity upon you I shouldn't say force the
00:39:55.360 strength of the gravity and we can measure strength the strength of gravity in various
00:39:59.680 different ways one ways to talk about the acceleration due to gravity the number that's normally
00:40:03.600 used is 9.8 ish now the units can be Newton's per kilogram but equivalently we can talk about
00:40:11.760 9.8 meters per second squared okay that's the number that's the value of gravity if there was
00:40:17.520 such a thing as the surface of Jupiter the value would be higher you would feel heavier
00:40:22.880 and if you went to the moon the value is about one fifth of what it is here on earth and so
00:40:27.200 therefore you feel lighter now the equivalence principle basically says this that if the value here
00:40:32.560 on the surface of earth is 9.8 meters per second squared when you're just sitting there in a
00:40:38.400 chair on the surface of the earth then if you go into deep space somewhere although where you are
00:40:44.320 weightless so to speak far from any gravitational body then if you wanted to replicate what it was
00:40:51.760 like on earth all you would need to do would be to accelerate at the rate of 9.8 meters per second
00:40:58.160 squared so you could stick yourself in a box and if you are unable to see outside if it was a
00:41:03.920 solid metal box then there would be no experiment that you could do inside the box to tell the
00:41:09.520 difference between whether you're in a box in deep space accelerating at 9.8 meters per second
00:41:14.080 squared or on the surface of the earth completely stationary but subject to the gravitational field
00:41:19.200 of the earth of 9.8 meters per second squared that's the equivalence principle in other words
00:41:23.840 accelerations and gravitational fields are equivalent in that way even though we can tell by
00:41:31.440 looking at them that the cause of the two different things is somewhat different now what's that
00:41:36.080 got to do with anything at all well if you want to simulate literal weightlessness here on earth
00:41:41.680 with a virtual reality machine you've got some problems to overcome and perhaps those problems are
00:41:48.000 impossibly high in terms of even in principle being able to overcome on earth if an astronaut wants
00:41:54.560 to train in weightlessness then what they have to do is to get into an aeroplane and the
00:41:58.160 aeroplane follows a parabolic path David explains this and the descent of the parabolic path
00:42:02.560 can be such that you can experience literal weightlessness there's no longer a gravitational field
00:42:07.680 acting upon your body and so you feel weightless you are weightless you will not register upon
00:42:12.720 a scale we also call that freefall in other words the best that a flight simulator on earth could do
00:42:18.720 if it wants to give you that sensation would be aside from getting directly into your brain of
00:42:24.160 course if it was able to somehow get directly into your brain would be on virtual reality then
00:42:29.040 how then it could give you the sensation of weightlessness however the only other way would be to
00:42:32.800 put the flight simulator itself into freefall which obviously means you'd want the flight simulator
00:42:39.440 at high altitude and then you're not simulating weightlessness you are weightless but how to simulate
00:42:44.560 freefall on the ground David asks and let me just read this section he says how to simulate it well
00:42:50.560 quote not easily for the laws of physics getting the way known physics provides no way other
00:42:55.600 than freefall even in principle of removing an object's weight the only way of putting a flight simulator
00:43:01.120 into freefall while it remained stationary on the surface of the earth would be somehow to suspend
00:43:06.080 a massive body such as another planet of similar mass or a black hole above it even if this were
00:43:12.560 possible remember we are concerned here not with immediate practicality but with what the laws of
00:43:18.320 physics do or do not permit a real aircraft could also produce frequent complex changes in the
00:43:25.040 magnitude and direction of the occupants white by maneuvering or switching its engines on and off
00:43:30.240 to simulate these changes the massive body would have to be moved around just as frequently
00:43:35.760 and it seems likely that the speed of light if nothing else would impose an absolute limit on how
00:43:42.080 fast this could be done and then David goes on to explain the approximations that we use you know
00:43:47.840 going underwater for example gives you an approximation but it's a crude approximation to
00:43:52.400 weightlessness so we can ignore those and he ends up concluding by saying or asking quote but could
00:43:57.360 one ever render the experience perfectly in a flight simulator that remained firmly on the ground
00:44:02.080 if not then there would be an absolute limit on the fidelity with which flying experiences
00:44:06.800 can ever be rendered artificially to distinguish between a real aircraft and a simulation a pilot
00:44:13.680 would only have to fly it in freefall trajectory and not see where the weightlessness occurred or
00:44:19.440 not then skipping a little David goes on to say weightlessness and all other sensations can
00:44:24.960 in principle be rendered artificially eventually it will become possible to bypass the sense organs
00:44:30.800 altogether and directly stimulate the nerves that lead from them to the brain so we do not need
00:44:36.560 general purpose chemical factories or impossible artificial gravity machines when we have understood
00:44:41.840 the old factory organs well enough to crack the code in which they send signals to the brain
00:44:46.240 when they detect sense a computer with suitable connections to the relevant nerves could send the
00:44:51.600 brain the same signals then the brain could experience the sense without the corresponding chemicals
00:44:56.640 ever having existed similarly the brain could experience the authentic sensation of weightlessness
00:45:02.560 even under normal gravity and of course no televisions or headphones would be needed or either
00:45:07.760 thus David goes on to say the laws of physics impose no limit on the range and accuracy of image
00:45:12.720 generators there is no possible sensational sequence of sensations the human beings are capable
00:45:17.600 of experiencing that could not in principle be rendered artificially thus the laws of physics
00:45:22.560 impose no limits on the range and accuracy of image generators one day as a generalization of
00:45:27.200 movies there will be what Aldous Huxley and Brave New World called Feelies movies for all the
00:45:32.880 senses one will be able to feel the rocking of a boat beneath one's feet hear the waves and smell
00:45:38.000 the sea see the changing colors of the sunset on the horizon and feel the wind in one's hair
00:45:43.280 whether or not one has any hair or without leaving dry land or venturing out of doors not only
00:45:48.480 that feelies will just as easily be able to depict scenes that have never existed and never could
00:45:53.920 exist or they could play the equivalent of music beautiful abstract combinations of sensations
00:45:59.120 composed to delight the senses that every possible sensation can be artificially rendered as one
00:46:04.560 thing that it will one day be possible once and for all to build a single machine that can render
00:46:10.080 any possible sensation calls for something extra universality a feeling machine with that
00:46:15.440 capability would be a universal image generator okay then David goes on talk about the possibility
00:46:22.160 of creating these universal image generators and so I'm skipping a bit there again we go into
00:46:28.640 the limits of technology the the the the the parochial limits of technology at any given time how
00:46:34.480 good our audio reproduction happens to be so skipping that picking it up where David writes quite
00:46:39.680 if an image generator is playing a recording taken from life it's accuracy maybe defined as the
00:46:45.360 closeness of the rendered images to the ones that a person in the original situation would have
00:46:50.960 perceived more generally if the generator is rendering artificially designed images such as a cartoon
00:46:56.240 or music played from a written composition the accuracy is the closeness of the rendered images
00:47:01.680 to the intended ones by closeness remain closeness as perceived by the user if the rendering is
00:47:07.520 so close has to be indistinguishable by the user from what is intended then we call it perfectly
00:47:13.840 accurate so a rendering that is perfectly accurate for one user may contain inaccuracies that are
00:47:19.440 perceptible to a user with sharper sensors or with additional sensors pause their mind reflection
00:47:25.040 and one might also add and more knowledge as well I'd can certainly imagine listening to a piece
00:47:30.960 of music that I think he's a perfect representation a perfect rendering of a previous piece
00:47:36.320 but not knowing that much about music I imagine someone else who has better knowledge
00:47:41.200 of music even if they don't have sharper sensors than they would be able to tell the difference
00:47:46.240 kind of skipping a bit David goes into what a universal image generator amounts to you know
00:47:51.280 this is the same as a computer all all actual computers we call them universal computers but of
00:47:56.080 course all actual computers to to approximations to universal computers to be a truly universal
00:48:01.600 computer you need an infinite amount of memory in order to you know literally any possible
00:48:05.920 computation that is possible well that includes computations that might last for the you know the
00:48:10.880 length of the universe so therefore you need a lot of you know memory in order to do that the
00:48:14.320 same is true for this universal image generator would need something so an amount of memory that
00:48:20.400 allows it to play a recording of unlimited duration as David says and so would need to be able to
00:48:27.600 maintain itself as it goes along as well so I'm skipping bits here and I'll pick it up where David
00:48:32.800 writes quote the human mind affects the body and the outside world by emitting nerve impulses
00:48:38.480 therefore a virtual reality generator can in principle obtain all the information it needs about
00:48:43.040 what the user is doing by intercepting the nerve signals coming from the user's brain those signals
00:48:47.920 which would have gone to the user's body can instead be transmitted to a computer and coded
00:48:53.200 to determine exactly how the user's body would have moved the signals sent back to the brain by
00:48:58.480 the computer can be the same as those that would have been sent by the body if it were in the
00:49:04.240 specified environment if the specification called for it the simulated body could also react
00:49:10.000 differently from the real one for example to enable it to survive in simulations of environments
00:49:15.120 that would kill a real human body or to simulate mouth functions of the body I had better admit
00:49:20.160 here that it is probably too great an idealization to save the human mind interacts with the
00:49:24.400 outside world only by emitting and receiving nerve impulses there are chemical messages passing
00:49:30.320 in both directions as well I am assuming that in principle those messages could also be intercepted
00:49:35.360 and replaced at some point between the brain and the rest of the body thus the user would lie
00:49:39.520 motionless connected to the computer by having the experience of interacting fully with the
00:49:44.160 simulated world in effect living there okay pausing their my reflection this is as David goes on to say
00:49:50.080 basically talked about in daycarts meditations with the team and the demon is intercepting your
00:49:55.520 senses your brain whatever and perhaps make deceiving you about the real nature of the world this
00:50:00.960 exactly the same thing is true in the matrix the movie by the Wachowski brothers that the matrix
00:50:05.680 movie the series of movies where human beings might be laying in pods and their their their
00:50:12.480 nervous system has a cable attached to it which intercepts these signals going to and from the brain
00:50:18.480 to make you think that you're experiencing a full 3d reality world but in fact you are laying in a
00:50:24.720 pod somewhere as the fuel source or the energy source for a great nefarious computer
00:50:31.840 same idea so skipping lots more and I'm just picking it up where David says quote
00:50:37.120 I do not want to understate the practical problems involved in intercepting all the nerve signals
00:50:41.840 passing into and out of the human brain and in cracking the various codes involved but this is a
00:50:46.400 finite set of problems that we shall have to solve once only after that the focus of virtual reality
00:50:52.240 technology will shift once and for all to the computer to the problem of programming it to render
00:50:57.200 various environments what environments we shall be able to render will no longer depend on what
00:51:02.560 sensors and image generators we can build but only on what environments we can specify
00:51:08.080 specifying an environment will mean supplying a program for the computer which is the heart of
00:51:13.440 the virtual reality generator end quote then David goes on to say how a virtual reality generator
00:51:19.040 unlike an image generator virtual reality generator responds to the users movements and so on
00:51:26.160 inside that environment what the user chooses to do and by way of further exploring this
00:51:31.280 idea David talks about playing tennis and so he says quote the number of possible tennis games
00:51:37.520 that can be played in a single environment that is rendered by a single program is very large
00:51:42.720 consider a rendering of the center court had Wimbledon from the point of view of a player
00:51:47.280 suppose very conservatively that in each second of the game the player can move in one of two
00:51:53.040 perceptibly different ways perceptibly that is to the player then after two seconds there are four
00:51:58.240 possible games after three seconds eight possible games and so on after about four minutes the
00:52:02.880 number of possible games that are perceptibly different from one another exceeds the number of
00:52:08.640 atoms in the universe and it continues to rise exponentially for a program to render that one
00:52:13.600 environment accurately it must be capable of responding in any one of those myriad perceptibly
00:52:19.520 different ways depending upon how the player chooses to behave if two programs respond in the
00:52:24.880 same way to every possible action by the user then they render the same environment if they would
00:52:31.120 respond perceptibly different to even one possible action they render different environments
00:52:36.080 that remains so even if the user never happens to perform the action that shows up the difference
00:52:41.680 the environment of program renders for a given type of user with a given connecting cable
00:52:47.200 is a logical property of the program independent of whether the program is ever executed
00:52:52.000 a rendered environment is accurate insofar as it would respond in the intended way to every
00:52:57.440 possible action of the user thus its accuracy depends not only on experiences which users of it
00:53:03.840 actually have but also on experiences they do not have but would have had if they had chosen
00:53:11.600 to behave differently during the rendering this may sound paradoxical but as I have said it is a
00:53:18.400 straightforward consequence of the fact that virtual reality is like reality itself interactive
00:53:24.080 this gives rise to an important difference between image generation and virtual reality generation
00:53:28.960 the accuracy of an image generator's rendering can in principle be experienced measured
00:53:34.000 and certified by the user but the accuracy of a virtual reality rendering never can be for example
00:53:41.440 if you are a music lover and you know a particular piece well enough you can listen to a performance
00:53:46.960 of it and confirm that it is a perfectly accurate rendering in principle down to the last note
00:53:52.560 phrasing dynamics and all but if you are a tennis fan who knows Wimbledon center court perfectly
00:53:58.240 you can never confirm that a purported rendering of it is accurate even if you are free to explore
00:54:04.240 the rendered center court for however long you like and to kick it in whatever way you like
00:54:09.360 and even if you have equal access to the real center court for comparison you cannot ever certify
00:54:14.720 that the program does indeed render the real location for you can never know what would have
00:54:20.240 happened if only who had explored a little more or looked over your shoulder at the right moment
00:54:25.120 perhaps if you had sat on the rendered umpire's chair and shouted fault a nuclear submarine would
00:54:31.840 have surfaced through the grass and torpedoed the scoreboard end quote so what's David saying there
00:54:37.040 well obviously that wouldn't happen on the real center court so if it happened in the rendered
00:54:42.880 centered court then center court at Wimbledon you know if you yell fault in the umpire's chair
00:54:48.160 and the nuclear submarine rises then clearly it's not an accurate rendering of the actual center
00:54:53.120 court where that thing would not have happened okay let's get going quote on the other hand
00:54:58.880 if you find even one difference between the rendering and the intended environment you get
00:55:03.680 immediately certify that the rendering is inaccurate unless that is the rendered environment
00:55:09.440 has some intentionally unpredictable features for example a roulette wheel is designed to be
00:55:14.640 unpredictable if we make a film of roulette being played in a casino that film may be said to be
00:55:20.000 accurate if the numbers that are shown coming up in the film are the same numbers that actually
00:55:25.440 come up when the film was made the film will show the same numbers every time it is played it is
00:55:30.080 totally predictable so an accurate image of an unpredictable environment must be predictable
00:55:36.640 but what does it mean for a virtual reality rendering of a roulette wheel to be accurate as before
00:55:42.480 it means that a user should not find it perceptibly different from the original but this implies
00:55:48.080 that the rendering must not behave identically to the original if it did either it or the original
00:55:54.720 could be used to predict the others behavior and then neither would be unpredictable nor must it
00:56:00.720 behave the same way every time it is run a perfectly rendered roulette wheel must be just as usable
00:56:07.680 for gambling as a real one therefore it must be just as unpredictable also it must be just as fair
00:56:12.720 that is all the numbers must come up purely randomly with equal probabilities how do we recognize
00:56:18.080 unpredictable environments and how do we confirm purportedly random numbers are distributed fairly
00:56:22.800 well we check whether a rendering of a roulette wheel meets its specifications in the same way
00:56:28.160 that we check whether the real thing does by kicking spinning it and seeing whether it responds as
00:56:33.280 advertised we make a large number of similar observations and perform statistical tests on these
00:56:39.200 outcomes again however many tests we carry out we cannot certify that the rendering is accurate
00:56:44.080 or even that it is probably accurate for however randomly the numbers seem to come up they may
00:56:49.120 nevertheless fall into a secret pattern that would allow a user in the know to predict them
00:56:54.400 or perhaps if we had asked out loud the date of the Battle of Waterloo the next two numbers that
00:56:59.520 came up would invariably show that date 18 15 on the other hand if the sequence that comes up
00:57:05.920 looks unfair we cannot know for sure there it is but we might be able to say that the rendering is
00:57:11.760 probably inaccurate for example if zero came up on our rendered roulette wheel on 10 consecutive
00:57:16.480 spins we should conclude that we probably do not have an accurate rendering of a fair roulette wheel
00:57:22.000 pause there my reflection you have to read all of these in concert with perhaps my recent
00:57:29.680 episodes on probability including the chapter on probability from Stephen Pinker's book
00:57:35.040 Rationality and more importantly perhaps the one before that where I go through David's talk
00:57:39.760 on probability all of this that same meaning is conveyed what David says he conveys precisely
00:57:46.400 the same meaning as I think he would otherwise phrase things now because yeah his take is that
00:57:51.600 probability is not a genuine thing it's a scam but it's a better way to talk about these things in
00:57:57.760 the same way so the roulette wheel a fair roulette wheel is subjectively unpredictable we can't
00:58:02.880 predict where it's going to go next because of the quantum world the quantum laws or physics
00:58:08.000 are the things that mean that from our vantage point we just don't know what number is going to
00:58:13.920 come up next but that's not to say it is literally random literally random and he probably
00:58:18.640 wouldn't say the word probably so often I don't know what we would say here is where he says
00:58:24.240 let me just read it again for example he says quote for example if zero came up on our rendered
00:58:30.240 roulette wheel on 10 consecutive spins we should conclude that we probably do not have an accurate
00:58:35.120 rendering of a fair roulette wheel and quote I would say that one phrasing that we could use
00:58:41.840 instead of using word probably there is if you have 10 consecutive zeros coming up on a roulette
00:58:47.120 wheel a bad explanation is that that was just due to chance one should instead hedge for have
00:58:55.120 the conjecture that there's been a stitch up that it's a put up job that someone is cheating
00:59:00.640 and so on and so forth whatever way you want to say this what isn't the cases that it's the best
00:59:05.520 explanation is that's not a fair roulette wheel we don't have to have any probably about it it's
00:59:11.520 not a fair roulette wheel would be our working hypothesis until such time as someone can show us
00:59:16.320 then in fact it is a fair roulette wheel however they go about doing that let's get going David
00:59:20.720 writes quote when discussing image generators I said that the accuracy of a rendered image depends
00:59:25.840 upon the sharpness and other attributes of the user's senses with virtual reality that is the
00:59:31.200 least of our problems certainly a virtual reality generator that renders a given environment
00:59:36.160 perfectly for humans will not do so for dolphins or extraterrestrials to render a given
00:59:41.040 environment for a user with given types of sense organs they virtual reality generator must be
00:59:46.320 physically adapted to such sense organs and its computer must be programmed with their characteristics
00:59:52.800 end quote yes so that's interesting so we have particular range of senses and then other organisms
00:59:58.800 will have subtly different range of senses so it's no good having a virtual reality generator
1:00:04.720 that is sending us the sensation of seeing ultraviolet or infrared radiation we can't see those
1:00:10.880 things so the whole concept of accuracy here is a virtual reality rendering is accurate
1:00:16.000 for a particular user and if the particular user can't tell the difference between that thing
1:00:20.720 and the real thing then it's accurate as David goes on to say quote this discussion of accuracy
1:00:27.360 in virtual reality mirrors the relationship between theory and experiment in science
1:00:31.520 thereto it is possible to confirm experimentally that a general theory is false but never that
1:00:38.240 it is true and thereto a short-sighted view of science is that it is all about predicting
1:00:43.760 our sense impressions the correct view is that while sense impressions always play a role
1:00:48.560 what science is about is understanding the whole of reality of which only an infinitesimal
1:00:53.920 proportion is ever experienced pause their my reflection there we go again there we have the
1:00:59.760 beginning of an infinity prefaced in or a deep theme of the beginning of a new prefaced in
1:01:05.280 here the fabric of reality again he says what science is about is understanding the whole of reality
1:01:13.600 understanding so there we get explanations an explanation allows you to understand reality and
1:01:20.000 we only ever experience an infinitesimal proportion of it so this small amount of data that we
1:01:26.400 are able together that's the stuff that gives us our problems or allows us to distinguish between
1:01:32.720 the theories we already guess and those theories can be about all of reality wonderful
1:01:39.120 David goes on to say the program and virtual reality generator embodies a general predictive theory
1:01:44.720 of the behavior of the rendered environment the other component deal with keeping track of what the
1:01:50.240 user is doing and with the encoding and decoding of sensory data these as I have said are relatively
1:01:56.160 trivial functions thus if the environment is physically possible rendering it is essentially
1:02:01.520 equivalent to finding rules for predicting the outcome of every experiment that could be
1:02:05.440 performed in that environment because of the way in which scientific knowledge is created
1:02:10.240 ever more accurate predictive rules can be discovered only through ever better explanatory
1:02:16.480 theories so accurately rendering a physically possible environment depends on understanding its
1:02:22.160 physics the converse is also true discovering the physics of an environment depends upon creating
1:02:28.640 a virtual reality rendering of it normally one would say that scientific theories only describe
1:02:34.320 and explain physical objects and processes but do not render them for example an explanation
1:02:39.680 of eclipses of the Sun can be printed in a book a computer can be programmed with astronomical
1:02:44.320 data and physical laws to predict and eclipse and to print out a description of it but rendering
1:02:49.200 the eclipse in virtual reality would require both further programming and further hardware
1:02:55.680 however those are already present in our brains the words numbers printed by the computer
1:03:01.680 amount to descriptions of an eclipse only because someone knows the meanings of those symbols
1:03:07.360 that is the symbols evoke in the reader's mind some sort of likeness of some predicted
1:03:12.800 effect of the eclipse against which the real appearance of that effect will be tested
1:03:17.280 moreover the likeness that is a vote is interactive one can observe an eclipse in many ways
1:03:23.360 with the naked eye or by photography or using various scientific instruments from some positions
1:03:28.160 on earth one will see a total eclipse of the Sun from other positions a partial eclipse and from
1:03:33.360 anywhere else no eclipse at all in each case an observer will experience different images
1:03:38.320 any of which can be predicted by the theory what the computer's description of folks in the
1:03:42.560 readers mind is not just a single image or a sequence of images but a general method of creating
1:03:48.480 many different images corresponding to the many ways in which the reader may contemplate making
1:03:53.680 observations in other words it is a virtual reality rendering thus in a broad enough sense taking
1:04:01.040 into account the processes that must take place inside the scientist mind science and the virtual
1:04:05.760 reality rendering of physically possible environments are two terms to noting the same activity
1:04:11.440 pausing their my reflection there's a depth to that that we can't just brush aside that science
1:04:19.840 and the virtual reality rendering of physical reality physically possible environments are two terms
1:04:25.680 to noting the same activity science this capacity to explain the universe is a virtual reality
1:04:32.560 rendering inside of our minds of what's going on in physical reality that's what a human's mind is
1:04:38.880 doing what a scientist mind is doing when they explain the world they are rendering physical reality
1:04:45.040 a version of physical reality to some degree of fertility to some degree of accuracy inside of their
1:04:51.520 own minds and this gets to the heart of this idea of humans as universal explainers yet of course
1:04:59.200 I think to be discovered by David yet there doesn't come until between here and the beginning
1:05:03.280 of infinity but we're getting hints of it there aren't we we're really getting hints of it there
1:05:07.040 David goes on to talk about virtual reality machines that render physically impossible environments one
1:05:12.240 of which is of course you know flying an airplane faster than the speed of light that is
1:05:17.040 something that a virtual reality generator can do it can render that environment now who cares about
1:05:23.360 that well let's read what David has to say about these reflections on this idea of physically
1:05:28.720 impossible environments being rendered in virtual reality consider a virtual reality generator
1:05:34.160 in the act of rendering a physically impossible environment it might be a flight simulator
1:05:37.760 running a program that calculates the view from the cockpit of an aircraft that can fly faster
1:05:43.280 than light the flight simulator is rendering that environment but in addition the flight simulator
1:05:48.080 is itself the environment that the user is experiencing in the sense that it is a physical object
1:05:53.840 surrounding the user let us consider this environment clearly it is a physically possible environment
1:05:59.440 is it a renderable environment of course in fact it is exceptionally easy to render one simply
1:06:04.960 uses a second flight simulator of the same design running the identical program under those
1:06:09.360 circumstances the second flight simulator can be thought of as rendering either the physically
1:06:14.240 impossible aircraft or a physically possible environment namely the first flight simulator
1:06:19.680 similarly the first flight simulator could be regarded as rendering a physically possible
1:06:23.760 environment namely the second flight simulator if we assume that any virtual reality generator
1:06:28.400 that can in principle be built can in principle be built again then it follows that every virtual
1:06:33.120 reality generator running any program in its repertoire is rendering some physically possible
1:06:38.720 environment it may be rendering other things as well including physically impossible
1:06:43.440 environments but in particular there is always some physically possible environment that
1:06:47.760 it is rendering so which physically impossible environments can be rendered in virtual reality
1:06:52.880 precisely those that are not perceptibly different from physically possible environments therefore
1:06:57.920 the connection between the physical world and the worlds that are renderable in virtual reality
1:07:01.680 is far closer than it looks we think of some virtual reality renderings as depicting fact
1:07:07.200 and others as depicting fiction but the fiction is always an interpretation in the mind of
1:07:12.560 the beholder there is no such thing as a virtual reality environment that the user would be
1:07:17.280 compelled to interpret as physically impossible okay then David goes on to talk about how virtual
1:07:22.080 reality could be used to render environments where the laws of physics are different so in theory
1:07:27.840 sort of physically impossible environment however the mere fact that some virtual reality
1:07:33.280 machine can render that environment makes it a physically possible environment because
1:07:37.520 look the virtual reality machine is rendering that environment so therefore it's physically
1:07:41.520 possible to render the environment so you're having an experience which is physically possible
1:07:45.680 not physically impossible in a sense and David talks about how imagination is a straightforward
1:07:51.840 form of virtual reality and goes on to say quite I'll pick it up where he starts to say quote we
1:07:57.360 realist take the view that reality is out there objective physical and independent of what we
1:08:02.800 believe about it but we never experienced that reality directly every last scrap of our external
1:08:08.480 experiences of virtual reality and every last scrap of our knowledge including our knowledge
1:08:12.880 of the non-physical worlds of logic mathematics and philosophy and of imagination fiction art and
1:08:18.640 fantasy is encoded in the form of programs of the rendering of those worlds on our brain's own
1:08:24.000 virtual reality generator so it is not just science reasoning about the physical world that involves
1:08:30.080 virtual reality all reasoning all thinking and all external experience are forms of virtual reality
1:08:36.800 these things are physical processes which so far have been observed in only one place in the
1:08:41.440 universe namely the vicinity of the planet earth we shall see and chapter eight that all living
1:08:47.280 processes involve virtual reality too but human beings in particular have a special relationship
1:08:52.960 with it biologically speaking the virtual reality rendering of their environment is the characteristic
1:08:57.760 means by which human beings survive in other words it is the reason why human beings exist
1:09:04.000 the ecological niche that human beings occupy depends on virtual reality as directly and as
1:09:10.400 absolutely as the ecological niche that koala bears occupy depends on eucalyptus leaves
1:09:15.920 end quote end of the chapter and there once again we have a hint I I I window into the beginning
1:09:25.120 of infinity because there the characteristic means by which human beings survive what is it a
1:09:29.680 virtual reality rendering of their environment and what is that and understanding of the physics
1:09:36.240 of the environment of all of everything not just the physics but of what the virtual reality
1:09:40.800 rendering of their environment is the explanations of their environment the explanations of the
1:09:44.720 physical world and not just the physical world but the other parts the other aspects of the world
1:09:49.360 the social world in which you occupy that you occupy the philosophical world that you occupy
1:09:53.760 the traditions and the culture that you occupy if that is being rendered inside of your mind
1:09:58.480 the understanding that you have inside of your mind the set of explanations that forms your
1:10:04.400 worldview is essentially a virtual reality rendering of your environment which is connecting this
1:10:11.600 book the fabric of reality to the beginning of infinity David says there again koala bears I think
1:10:16.720 it's not the first time that he said koala bears in this book and every Australian
1:10:21.840 every Australian of course bogs at koala bears but I'm not going to get into it people can't even
1:10:26.640 agree at the moment on what boys and girls means so whether or not koalas are bears or not I think
1:10:31.280 can be passed over in silence but that is the end of the chapter let me read the summary at the
1:10:36.560 end of the chapter here David writes virtual reality is not just a technology in which computers
1:10:41.920 stimulate the behavior of physical environments the fact that virtual reality is possible is an
1:10:46.880 important fact about the fabric of reality it is the basis not only of computation but of human
1:10:52.080 imagination an external experience science mathematics art in fiction what are the ultimate limits
1:10:58.320 the full scope of virtual reality and hence of computation science and imagination the rest
1:11:02.640 in the next chapter we shall see that in one respect the scope of virtual reality
1:11:07.600 is limited while in another it is drastically circumscribed goodbye