00:00:00.000 the Nexus. What is a person? People are different. I do not mean one from
00:00:08.920 another, although they are that, but they are different in kind to everything
00:00:13.360 else in the universe, starkly different. It's not like cockroaches are a little
00:00:17.800 different from ants, bees are a little different again, hummingbirds, different
00:00:22.320 still, then parrots. Flying foxes still fly, but they're a little bit different,
00:00:26.840 perhaps more so, cats different again, koalas look more cuddly as we move along
00:00:32.240 the continuum than monkeys. And so the smooth transition of differences goes
00:00:38.280 onto chimpanzees and bonobos, and we're just next, right? No. Everything was
00:00:46.560 more or less fine until the claim that we're next, as if we're on the same
00:00:51.640 continuum. We are not. In the same way that the leaf still growing on the branch
00:00:57.520 is different in kind to the rocks below, or indeed the plant different to the
00:01:02.280 bee in kind, so are we different to all other species. Yes, rocks and leaves
00:01:09.600 have some similarities, both are made of atoms, but so much for that. It is the
00:01:15.240 differences that really matter. Life and non-life are different in kind, there are
00:01:20.680 many ways school students learn of the differences, but the real difference
00:01:25.080 between the living and the never was alive, come down to the presence or
00:01:30.040 absence of genetic information. Life grows, life reproduces, life passes on
00:01:36.200 information from one generation to the next, and that information it passes on
00:01:40.440 is in response to encounters with the environment. Plants and animals are
00:01:45.600 different in kind too. Do we need to spell out the ways? I guess some might need
00:01:50.200 to be reminded. Plants utilize photosynthesis. They are autotrophs. They can make
00:01:55.120 their own food. Animals cannot do this. They must physically move from place
00:02:01.080 to place in order to eat. Animals tend to have somewhat more complex nervous
00:02:05.440 systems while plants lack almost any sign of having sense organs. That's not
00:02:09.800 to say they have none, but compared to an animal, it's not much. They cannot
00:02:13.800 encode information about the environment around them and represent it in some
00:02:18.240 way in a nervous system, which is to say in a computer of a kind. Whatever the
00:02:24.000 case, I labour this point because it is clear to people, I guess, because they
00:02:28.160 are taught this among other things, that there is a clear line to be drawn
00:02:31.240 between the living and the non-living, and then within the living between the
00:02:34.920 plants and the animals. Both the non-living and the living have many
00:02:38.920 similarities and we could list them. So too with plants and animals, but does
00:02:43.760 anyone doubt that it is the differences that are the really interesting thing
00:02:47.680 here? But humans are unique for another reason. They often want to deny how
00:02:52.440 unique the hours are species, we stand apart from all other life on earth. On the
00:02:57.480 one hand, many will immediately recognise to the point of celebration all the
00:03:01.440 damage we can do to the planet, so we are taught. So on the one hand we are
00:03:05.840 different in kind, we are uniquely destructive, it is said. But even if we were
00:03:11.760 to grant this, where does that capacity for being uniquely destructive come
00:03:16.680 from? It comes from our capacity to control the environment around us. It comes
00:03:21.480 from our capacity to be uniquely creative. But where does that come from? It comes
00:03:27.240 from our capacity to explain it, to explain something means to give an account of
00:03:31.560 what really exists out there in the world and how those things that exist have
00:03:36.000 relationships between them which allow for the evolution over time of
00:03:40.160 physical systems. A person can not only explain the world in which it finds itself,
00:03:45.760 our world is such that it is always explicable by people. This follows from a
00:03:51.840 momentous discovery and science about the relationship between physics and
00:03:55.600 computation. Computation is that field of study concerned with how to
00:04:00.480 calculate the answer to mathematical problems. It was once thought that such a
00:04:04.240 field of study was itself part of pure mathematics. Being a part of pure
00:04:08.400 mathematics, it was further thought that it could be discussed without ever
00:04:11.400 worrying about what the laws of physics actually were. But how does a
00:04:15.480 computer do what it does? According to some histories of this and there are
00:04:19.240 competing stories, Alan Turing was the first to formalize a system of
00:04:23.760 computation. It's a simple idea. Take an infinitely long strip of paper. We're
00:04:29.000 doing pure mathematics here after all, so we can have infinitely long
00:04:32.600 scripts of paper. And divide it into squares. Each square is either blank or it
00:04:37.840 has a symbol on it. Now a computer on this view is now a device that can read
00:04:43.120 whether or not there is a symbol on the square or not. And further it can write a
00:04:47.560 new symbol or erase a symbol before moving on to the next square. Whether the
00:04:51.680 machine moves on to the next square, let's say to the right along the
00:04:54.640 strip or to the left or stops, all depends on the program that the programmer
00:04:59.360 has written for it instead of instructions. Now the remarkable thing about
00:05:03.960 such a device is that it can be instructed to compute anything that is
00:05:07.920 computable. No matter what the mathematical problem, if it is computable and not
00:05:12.680 all mathematical questions are computable, not by a long shot. If it is
00:05:16.680 computable, then the Turing machine can compute it. Indeed, Turing's whole
00:05:21.360 purpose was to solve a problem in pure mathematics. Mathematics, given what most
00:05:26.000 people thought then, and the popular conception now, is just a mechanical
00:05:29.760 process of following rules, the rules of inference or the rules of mathematics. So
00:05:34.320 then it should be possible for a machine to just do the maths by following the
00:05:37.880 rules for what sort of a mathematical problem could be posed to it. For reasons
00:05:42.520 beyond the scope of what I'm talking about here and now, that claim was shown to
00:05:46.400 be false. Mathematics is not purely mechanical. There are just some mathematical
00:05:50.840 questions the machine cannot find an answer to. For one reason, for some
00:05:55.640 questions, it will just run and run forever without ever being able to find the
00:05:59.920 answer. This is just one among many other issues involving the creativity of
00:06:04.720 mathematicians as being central to discovery of mathematical knowledge. Now
00:06:09.240 one amazing thing about the laws of physics as we know them, that they are
00:06:12.880 expressible mathematically as computable functions, Turing
00:06:17.080 computable functions. In other words, the laws of physics are, during
00:06:21.000 computable, by a Turing machine. And this is actually the answer to that
00:06:24.920 long-standing question posed by Eugene Wigner about the so-called unreasonable
00:06:29.840 effectiveness of mathematics in the natural sciences. The fact is that the laws of
00:06:33.880 physics, the laws of nature, are not only mathematically informed, but
00:06:38.160 during computable. So this is why mathematics is effective in the physical
00:06:41.880 sciences. The physical sciences, governed by physical laws, which are
00:06:45.160 in computable, and our mathematical process, or proof, is a kind of
00:06:49.240 computation. But a problem looms here. The laws of quantum theory reveal that
00:06:54.880 matter, even something as simple as the motion of electrons moving in place
00:06:58.800 around a nucleus is not so simple. The problem of how to compute the
00:07:03.520 position of the electrons at any time in the future, given their present state,
00:07:06.840 while computable, cannot be efficiently computed by a Turing machine, which is
00:07:11.920 to say, for problems like this, even if the Turing machine was operating at
00:07:16.520 the speed of light, it might still take the lifetime of the universe to
00:07:20.040 calculate where the electrons would be some minutes from now. As Richard
00:07:25.100 Feynman quipped about the early pioneers of computation, they thought they
00:07:28.720 understood paper, by which he meant that Turing machine itself is actually
00:07:33.240 a real machine. It is not merely imaginary or the product of pure
00:07:36.920 mathematical intuition or something like that, whatever that might be. It must be
00:07:41.280 made out of physical stuff, like paper, and that obeys the laws of quantum theory.
00:07:46.200 So it was David Deut, who in 1985 published a paper titled quantum theory, the
00:07:52.600 Church Turing thesis and the universal quantum computer, while Turing had
00:07:57.200 assumed that his machine operated according to classical laws of physics in a
00:08:01.800 kind of abstract space. Deut brought this down to earth. He applied the actual
00:08:07.400 laws of quantum theory that governed the universe to Turing's machine in a new
00:08:12.480 mode of computation was born. The Turing machine was still universal, that
00:08:17.840 did not change, but now it was made out of actual paper, or actual matter, and
00:08:23.040 not an idealized kind of abstract paper obeying fictional laws, but rather
00:08:27.920 stuff obeying the actual laws of physics. Quantum physics. Strangely enough, the
00:08:33.880 real world is even more powerful than Turing imagined because actual matter,
00:08:37.640 actual paper, so to speak, a proper understanding of the matter paper is made of
00:08:42.200 allowed for the efficient computation of things like electrons orbiting nuclei
00:08:47.760 in atoms. What might have taken the classical universal Turing machine, the
00:08:52.440 lifetime of the universe, might now take only minutes with a quantum computer for
00:08:57.440 some tasks. Like, for example, simulating or modeling quantum systems like atoms
00:09:02.480 or electrons interacting, thus was the birth of quantum computation, an entire
00:09:07.360 industry and a race to building the first universal quantum computer, which we
00:09:12.040 still do not have, but we will one day, because it is physically possible, so if
00:09:16.040 we just keep on correcting errors and improving our knowledge and technology,
00:09:19.840 whatever is not prohibited by the laws of physics is possible given the right
00:09:23.960 knowledge. But what this also means is that anything that exists in physical
00:09:28.680 reality can be simulated by a quantum computer, atoms can be, stars, solar
00:09:33.800 system, galaxies can be, whole universes can be, and anything in them, anything
00:09:38.440 including people, including their brains, the brain of a person as a physical
00:09:44.120 system, whatever it is doing, it is doing according to the laws of physics, and
00:09:48.280 because of this, it can, in principle, be simulated by a quantum computer. Now,
00:09:52.880 this might very well mean a quantum computer of the distant future could
00:09:56.240 simulate every atom in a human brain, and therefore replicate the processes in a
00:10:00.960 human brain inside of a quantum computer. What this might be like for such a
00:10:05.480 simulated brain is anyone's guess, but we should not deny that such a simulation
00:10:09.600 would be a person. A person is the software running on the brain, so a
00:10:13.880 simulation of a piece of software is that piece of software, so a simulation of
00:10:18.640 a person is a person. So therefore, a moral hazard is before us here that we
00:10:23.920 should be eager to solve long before we try to do such a thing. We're switching
00:10:28.600 off the simulation we like putting the person to death. We're switching it on
00:10:32.280 the form of torture. Absent human-like senses would the person in the
00:10:36.040 simulation be in a terrible night marriage void of nothingness or at a
00:10:39.160 confusion like a terrible but unending acid trip, somehow coupled with the
00:10:43.000 knowledge that one is being simulated? Would that person in the simulation have
00:10:47.160 all the memories of the physical brain that it has just simulated? Presumably so
00:10:51.800 and presumably that is reason enough never to try the experiment in precisely
00:10:56.800 this way. But it may be and we expect it to be the case that simulating every
00:11:02.040 single atom in a brain would not be needed to simulate a person. Instead we
00:11:05.880 just need to simulate that part of the brain that is doing actual
00:11:08.600 computations, in particular the necessary parts of the brain that are able to
00:11:12.800 conjecture explanations of everything else. That is what a person is after all a
00:11:17.200 universal explainer. If we can simulate just that part that is enough in
00:11:22.680 order to simulate a person in order to create a person. But we have very little
00:11:27.200 idea of course precisely where in the brain and how these computations are
00:11:31.640 performed nor more importantly what the program is then structs the brain to
00:11:36.760 compute from one moment to the next which is to say we do not know what the mind
00:11:41.720 is in terms of what the code might be. But what the algorithm might be written
00:11:46.120 to capture the process that is the mind. The process that generates knowledge
00:11:50.520 creates explanations seeks to comprehend the world around it. These are
00:11:54.840 also anonymous and we do not know what the code for any of them are. A person
00:11:59.760 uniquely unlike everything else in the known universe can create explanations.
00:12:04.360 Those explanations are a sign of the person gradually coming to comprehend the
00:12:08.600 world in which it finds itself. What does it mean to comprehend something
00:12:12.600 understanding? To comprehend or understand something is to complete a certain
00:12:19.040 kind of computation that is after all what the brain is doing it is computing
00:12:23.320 things that part of the brain that deals with computing models of the world
00:12:27.040 for explanations is the software more commonly referred to as the mind. Not all
00:12:32.560 the brain is a mind, conjecturing explanations, much is dealing with largely
00:12:36.360 unconscious processes, monitoring sleep cycles whether one is hungry and so on.
00:12:40.680 But the mind does seek to understand which means it seeks to create inside of
00:12:45.520 itself some kind of model of what is outside as well as inside. This is the sense
00:12:50.760 in which we say that if the laws of physics are comprehensible they must be
00:12:55.120 capable of being embodied in another physical object, the Noah. If the laws of
00:13:00.240 physics were such that they could not be embodied elsewhere like the mind of
00:13:03.680 person then this would mean the attempt to comprehend the laws of physics would
00:13:07.640 be impossible. But this is not the world we are in. We are in a world where
00:13:12.160 computation can be universal. There can be devices that can compute anything that
00:13:16.600 is computable. And the laws of physics are computable. They consist of
00:13:20.880 computable mathematical functions that simply is provably the case. There is
00:13:25.720 nothing in the standard model or quantum field theory or general relativity the
00:13:29.560 laws of thermodynamics construct a theory or string theory if you want to go
00:13:32.560 that way that contain within them. Non-computable functions. The functions used by
00:13:37.920 physics are computable. The laws of physics are computable as such a computer
00:13:41.400 can be programmed to simulate what the laws of physics are doing. One such
00:13:45.100 computer is the human brain. The human brain being able to explain things in
00:13:48.440 the first place to create knowledge is thus able and principle to comprehend to
00:13:52.400 understand those laws of physics. We might also wonder along with the British
00:13:56.640 historian Lord McCauley who wrote in response to the pessimists of his time on
00:14:01.120 what principle is it that with nothing but improvement behind us we are to
00:14:05.560 expect nothing but deterioration before us. We could paraphrase that wonderful
00:14:10.240 quib to how is it that with nothing but simplifications and
00:14:13.600 unifications behind us we are to expect the wall of complexity and
00:14:17.600 incomprehensibility before us. In other words our grand and deepest theories
00:14:23.120 explain more become more unified and are not impenetrably complex despite
00:14:28.120 what we have taught at school and university and the way in which we are taught
00:14:32.160 those things. Understanding is just a physical process. It is in truth identical to
00:14:38.680 the act of creating the knowledge in the first place that aha moment people
00:14:42.480 get when they understand something is precisely the same feeling as the
00:14:45.800 scientists who gets it for the first time ever. It is just different in degree
00:14:49.320 perhaps not in kind. The first person ever Einstein to understand that
00:14:54.200 accelerations and gravity are two sides of the same coin that for example and
00:14:58.160 elevator which is stationary on the ground will cause the occupants to
00:15:01.120 experience precisely the same sensations as the same elevator in deep space
00:15:04.920 accelerating at 9.8 meters per second per second. This is known as the
00:15:08.280 equivalent principle between gravitation and acceleration. He called this
00:15:11.760 his happiest thought. Now if you understand that same principle you may have a
00:15:16.280 happy thought too. A happy sensation of comprehension of course it's
00:15:20.520 tempered by the fact that well firstly you're not the first ever to have
00:15:23.840 understood that and secondly Einstein may of course have understood things a
00:15:28.360 little more deeply because he'd been pondering that same problem for hours a day
00:15:32.560 for years at a time and so his happy thought was probably deeper but not
00:15:38.040 different in kind whatever the case. Understanding is creating knowledge and
00:15:43.080 creating knowledge is a process that minds do it is about modeling being embodied
00:15:47.640 in a mind. This is where we talk about self similarity. The idea that a mind can
00:15:53.360 contain within it a working model of the rest of physical reality to some
00:15:57.360 arbitrary degree of accuracy. We are always scratching the surface so the model
00:16:01.720 is never perfect but in principle anything that exists can be represented or
00:16:05.960 embodied in the mind of a person including the person. This is the self
00:16:10.120 similarity part. A part of a person is just like in some respects the rest of
00:16:15.000 everything else and it becomes more and more like the rest of the time as it
00:16:18.960 learns more so I should just pause here and have a little diversion on this
00:16:24.120 concept of self similarity and self similarity is a concept out of
00:16:29.520 mathematics it's often used when discussing things like fractals. Fractals
00:16:34.680 being these patterns that are merged from rather simple mathematical
00:16:38.520 formula where no matter how much you magnify a part of the fractal it looks
00:16:45.440 the same as the part of the fractal that was not magnified. It continues to
00:16:50.480 repeat itself in a sense that the smaller parts are similar to the larger
00:16:55.400 parts of the fractal. In physical reality we have things like this as well.
00:17:00.440 Coastal lines for example the more that you magnify the coastal line the more
00:17:06.000 that it looks like the coastline from a greater distance away. It's self
00:17:10.560 similarly it's similar to itself. Now the kind of self similarity that's invoked
00:17:15.480 in the work of David Deutsch when it comes to knowledge and the laws of
00:17:19.720 physics is deeper than this. It's about how structures in the mind are similar
00:17:26.520 to other parts of physical reality and this is a kind of unique aspect to the
00:17:32.920 minds of people. The example that's used by David Deutsch is a wonderful one. He's
00:17:39.240 used it in his TED talk so he uses it in the beginning of infinity where he
00:17:42.880 compares our physical understanding of what's going on with a quasar. A quasar is
00:17:49.560 an extremely distant very luminous object which we think is a black hole
00:17:56.720 gradually consuming stars and as a consequence of this process of a
00:18:02.560 black hole consuming a star, a very violent high-energy process, vast quantities
00:18:08.480 of energy and light are produced and we can detect that from here on Earth. We
00:18:13.120 can see using our telescopes these extremely distant objects quasars,
00:18:17.480 quasies, stellar radio sources, more luminous than entire galaxies. Our most
00:18:22.640 powerful telescopes can see these quasars. What does that have to do with
00:18:27.400 self similarity? Well let's consider our knowledge of quasars. Let's consider
00:18:31.720 our understanding of what a quasar really is. Our understanding of what a
00:18:35.960 quasar really is is as I described a black hole consuming stars and as a
00:18:42.480 consequence the accretion disk which is the disk of material that is falling
00:18:48.280 into the black hole is rotating so quickly that it creates magnetic field. The
00:18:53.120 reason it creates magnetic field is because this gas that is spiraling into the
00:18:58.280 black hole is ionized, ionized gas. Ionized gas means you have an electrical
00:19:04.680 current of a kind and ion is a charged particle so lots of the moving together
00:19:09.680 constitute an electric current and all the way back in the 1800s we had people
00:19:14.560 like Michael Faraday explaining how moving charges like electrons or in
00:19:20.200 this case ions can generate magnetic field. These magnetic fields that are
00:19:24.880 generated caused a production of jets of material to head in all directions
00:19:30.320 but in our case towards the earth which we can see which we can detect and
00:19:34.920 which allow us of course via our telescopes via the detection of this light to
00:19:39.400 thereby understand the process which is producing this phenomena that we see.
00:19:44.840 So out there in reality we have this thing called a quasar which is an extremely
00:19:51.000 violent, unusual object and as David says the physics of the quasar could not
00:19:56.840 be more unlike the physics of the brain. What's it's got to do with self-similarity?
00:20:01.640 Well despite the fact that the physics of the quasar is so different to the
00:20:06.440 physics of the brain nonetheless there's something in the brain of the
00:20:11.800 relevant astrophysic with the relevant knowledge that is similar similar to
00:20:16.880 the quasar. What's similar? The mathematical relationships of the parts of the
00:20:23.240 explanation describing and explaining what's going on in that quasar is similar
00:20:29.240 to what is actually going on with the matter in the quasar. The matter in the
00:20:34.520 quasar is obeying physical laws and those physical laws have mathematical
00:20:40.400 relationships between them. The relationship between the physical forces and the
00:20:45.320 matter what is physically going on on the other side of the universe in that
00:20:49.600 quasar is replicated and similar to what's going on between the abstract
00:20:57.000 ideas and the mathematical relationships between those abstract ideas in the
00:21:01.640 mind of a physicist who understands the quasar and as we come to understand
00:21:05.840 quasars more and more the fidelity or the accuracy with which that explanation
00:21:12.680 comes to resemble the actual quasar out there increases over time. We gain a
00:21:19.080 more accurate model as we correct the errors in our understanding of that thing
00:21:24.200 over there. So this is what self-similarity is that structures separated not only
00:21:30.520 by distance but separated by the kind of matter and relationships that make
00:21:35.160 them up. In other words the relationships that make up what's going on in the
00:21:38.360 neurons inside the brain and the relationships between what's going on with the
00:21:42.920 particles of a created material from the star being consumed by the quasar come
00:21:48.160 to have a similarity between them. Not so much a superficial visual similarity
00:21:55.360 but rather a deeper similarity. There is a one-to-one correspondence between the
00:22:01.480 ideas of the astrophysicist coming to understand the quasar and the physical
00:22:07.320 processes going on inside the quasar. Now there's a further way in which this is
00:22:11.360 self-similarity of the universe. Namely not only does the astrophysicist over
00:22:17.440 time come to have a visual and mathematical representation, a model of the
00:22:23.880 quasar in their mind that increases in its accuracy over time as the astrophysicist
00:22:29.200 comes to learn more about that quasar but this is true of every physical
00:22:32.960 process in the entire universe. Everything that we begin to learn about we are
00:22:37.200 creating models of. So we are creating models of all the other stuff that's out
00:22:41.280 there in the universe inside of human minds. There are models of the rest of
00:22:46.920 physical reality. The human mind is coming to understand with increasing
00:22:51.520 fidelity over time the rest of physical reality. So the mathematical
00:22:56.040 relationships that exist out there between physical objects are coming to be
00:23:00.720 represented by abstract objects inside the mind of physicists. And a further level of
00:23:07.440 self-similarity is the human being, the person is coming to understand all the
00:23:12.080 stuff out there and the stuff that's in here as well. We come to understand our
00:23:16.560 own psychology better over time as well. This is of course just in its very
00:23:21.800 nascent beginnings, our understanding of our own mental state. But as that
00:23:25.600 increases as well then we kind of have this feedback between the self-similarity
00:23:31.480 in our minds of the rest of physical reality as well as ourselves which are
00:23:34.880 also part of physical reality. It's kind of a recursive learning that's going on
00:23:39.080 and so we are becoming more and more similar in terms of our knowledge to the
00:23:44.280 rest of objective reality out there. These two things are coming to resemble
00:23:49.000 each other in deep fundamental ways. Again we did not have a very good explanation
00:23:56.240 of exactly what a person is but a person is made of matter, obeying physical
00:24:00.920 laws and so that matter can be in principle simulated because the laws of
00:24:05.520 physics are true and computable and understanding is just a kind of
00:24:08.960 computation it is something minds do. This means the laws of physics are such
00:24:13.280 that they mandate their own comprehensibility which is an astonishing fact.
00:24:17.560 Logically it did not need to be this way it is not logically necessary that
00:24:22.080 the laws of physics be computable but they are that as a contingent empirical
00:24:26.320 fact about our world the laws of physics could have consisted of functions
00:24:30.560 not computable or the laws might have been such that computation was not
00:24:34.560 possible or that universal computation was not possible or quantum theory was
00:24:38.560 false in all sorts of ways or it could have been that there were two substances
00:24:42.200 in the world matter obeying physical laws and spirits in the spiritual world and
00:24:46.600 soul that does not that operated by means other than physical processes. Now some
00:24:50.560 people do insist on this it should be said whenever anyone says understanding
00:24:54.960 is not computing they are appealing to the supernatural they are saying that
00:24:58.840 something a mind does is not physical not governed by the laws of physics but
00:25:04.160 the rest of us are scientific realists we defer to the best explanation we do
00:25:08.280 not jump to supernatural ideas because we do not like the sound of what conclusions
00:25:13.680 follow from our best scientific theories we take our best scientific theories
00:25:17.920 seriously and so that matter can be in principle simulated because the laws of
00:25:27.680 physics are true and computable and understanding is just a kind of
00:25:30.920 computation it is something mine to do this means the laws of physics are such
00:25:35.720 that they mandate their own comprehensibility so let's unpack that claim
00:25:41.840 that the laws of physics mandate their own comprehensibility well we have to
00:25:48.760 begin with the notion that there is this law of physics there is this law of
00:25:54.520 physics proven mathematically by David Deutsch in his seminal 1985 paper
00:26:01.120 now that paper it's just remind ourselves of that paper it's titled quantum
00:26:07.520 theory the Church Turing principle and the universal quantum computer okay so
00:26:13.160 let's just consider what the Church Turing principle or hypothesis is what
00:26:19.600 Turing said the way Turing wrote it and I'm just quoting from David's paper
00:26:22.760 he said every function which would naturally be regarded as computable can
00:26:28.600 be computed by the universal Turing machine okay so that's what Turing
00:26:34.120 said with respect to his principle all computable things can be computed by a
00:26:42.280 Turing machine by a computer in other words it almost sounds like a
00:26:45.960 tautology it's a principle it wasn't proven until David proved it with this
00:26:52.720 paper and how did he prove it well he proved it by assuming rightly that
00:26:59.880 computers have to be made of stuff they have to be made of matter the matter
00:27:05.520 abays the laws of physics what are the laws of physics the quantum laws of
00:27:10.280 physics now does that mean the quantum laws of physics are the final forever
00:27:14.720 word on what the laws of physics are no so what he's doing is using our best
00:27:20.160 knowledge of what the laws of physics are now it could be wrong but what else
00:27:24.720 can we do it could be that general relativity is wrong it could be we're all
00:27:28.240 living in a simulation all these silly claims about we could be wrong of
00:27:32.120 course we always could be wrong but we don't make much progress assuming we're
00:27:36.760 wrong unless we have somewhere better to jump to unless someone has a better
00:27:40.360 idea simply assuming that our best knowledge is wrong doesn't get us very far
00:27:44.600 unless we and less we have something better to replace it with so assuming
00:27:48.720 quantum theory is correct then assuming that real physical computers are
00:27:56.360 Bay quantum theory applying quantum theory to computation we can make a few
00:28:04.080 other claims like for example the laws of physics consist of Turing
00:28:11.560 computable functions so this just simply is the case all the ways in which we
00:28:17.160 express the laws in quantum theory and elsewhere by the way but in quantum
00:28:21.840 theory in particular is via computable functions it's not like there's a law
00:28:27.040 of physics in quantum theory that is not computable it's computable which
00:28:31.560 means given that all matter conforms abays quantum theory then that means
00:28:38.200 any physical process that happens anywhere in the universe at any time is
00:28:42.800 going to be able to be computable by a Turing machine why because a
00:28:49.240 Turing machine a universal Turing machine operating via laws of
00:28:54.040 quantum theory is going to be able to simulate any physical system in the
00:29:00.440 universe made of physical stuff because that physical physical stuff is obeying
00:29:05.280 the laws of quantum theory the very laws which themselves are computable as
00:29:10.080 David says in his paper he says every fine-artly
00:29:13.440 realizable physical system can be perfectly simulated by a universal model
00:29:17.120 computing machine operating by finite means now this by the way has been
00:29:21.120 amended and I think he was I'm not sure if he was required to put something
00:29:26.200 like that in there by an editor or something but in fact the better way to
00:29:29.120 phrase that sentence is that every fine-artly realizable physical system can
00:29:35.680 be arbitrarily accurately simulated by a universal model computing machine
00:29:42.600 operating by finite means in other words every fine-artly
00:29:45.960 realizable physical system so every physical system that's out there
00:29:49.360 okay everything that really exists out there in the known universe can be
00:29:53.960 simulated to whatever degree of accuracy you like by a universal computing
00:29:59.720 machine okay a quantum computer can do this because inside of the quantum
00:30:04.880 computer you could have a simulation of an atom for example now this could
00:30:10.920 be done by a classical Turing computer you could have an atom simulated
00:30:16.800 inside of a classical laptop problem is that it's not going to be very
00:30:23.400 accurate at all it's going to be very very slow in order to calculate things
00:30:27.200 like where the electrons are from moment to moment why because where the
00:30:31.640 electrons are rounded nucleus are from moment to moment is governed by the
00:30:34.800 laws of quantum theory and it says that there are many many many many many
00:30:38.440 places that the electrons can be from moment to moment as they orbit the nucleus
00:30:42.400 this is one of the great insights of quantum theory so you presented with a
00:30:46.240 problem that although a normal computer a classical computer a classical
00:30:50.920 Turing machine operating according to the laws of classical physics would be
00:30:57.280 able to simulate an atom if you want to predict where the electrons are going
00:31:00.840 to be a minute from now around that nucleus what you're going to find is that
00:31:06.000 your classical computer is going to grind to a halt all the possibilities that
00:31:10.320 come together to enable you to predict the position and the velocity of these
00:31:15.040 electrons as they're going around the nucleus from moment to moment it's going
00:31:19.280 to exponentially spiral into and just a vast number of computations which will
00:31:26.240 slow down your computer so if you want to calculate where the electrons are
00:31:29.440 going to be a minute from now your computer is going to take years perhaps the
00:31:33.440 lifetime of the universe in order to do that however if you have a quantum
00:31:38.280 computer it can do it efficiently so if you want to predict where the electrons
00:31:42.280 are going to be a minute from now perhaps it can do that calculation in a few
00:31:46.760 minutes or in a few seconds something like that it can do it efficiently it's
00:31:49.920 not going to take the lifetime the universe can to do that because it can take
00:31:54.520 part in this quantum parallelism this this different mode of computation which
00:31:59.520 quantum computers allow for now extend that argument to any physical system not
00:32:05.880 just an atom not just trying to predict where the electrons are going to be
00:32:08.800 around an atom but now extended to ensembles like a collections of atoms
00:32:14.640 working together lots of atoms such as would exist in a human brain so a
00:32:21.000 quantum computer in theory could simulate the operation of a human brain of course
00:32:28.480 this is unfeasible right now but in principle in principle it's physically
00:32:32.280 possible for a quantum computer to simulate a physical brain therefore a human
00:32:38.160 being can be simulated a person can be simulated inside of a quantum computer
00:32:43.200 and everything that a human mind can do everything a human brain can do can be
00:32:47.840 simulated by a quantum computer what are some of the more interesting things
00:32:51.200 that a human brain can do or a human mind can do well probably the most
00:32:54.680 interesting thing it does for our purposes and our discussions what we're
00:32:57.960 talking about with the creation of knowledge is comprehend things understand
00:33:03.360 things create explanations so this particularly unique interesting capacity
00:33:11.200 of the human mind namely the capacity to understand things in particular the
00:33:17.240 capacity to understand the laws of physics that's just one thing that the human
00:33:23.360 mind can do can be simulated by a quantum computer because a computer can
00:33:29.360 simulate any physical system including the human brain including the human
00:33:33.520 mind comprehension understanding is a kind of computation it's a thing that the
00:33:39.680 human brain does now the laws of physics mandate everything that can be done
00:33:45.120 right everything that can be done physically in the universe is something that
00:33:51.120 has been mandated to be done by the laws of physics the laws of physics have
00:33:56.240 mandated have said that orbits are approximately circular around the Sun that's
00:34:02.360 one thing the laws of physics are such that if I would drop an object here it
00:34:07.800 will go towards the ground rather than rise up towards the sky that's mandated by
00:34:13.240 the laws of physics the laws of physics mandate that electrons will repel each
00:34:18.160 other they mandate that electrons will be attracted towards protons positive
00:34:24.080 attracts negative okay there's all these things anything that happens is mandated
00:34:28.040 by the laws of physics mandated or another way of saying that is determined
00:34:32.360 determined to happen everything that happens is determined to happen now this is
00:34:37.960 not a full explanation of everything that happens it's it's a very it doesn't
00:34:43.280 get us very far to say that things are determined or mandated for example the
00:34:47.500 laws of physics are such they determine that whatever happens out there in
00:34:51.460 physical reality was determined to have happened by those animals or physics in
00:34:55.240 other words the creation of the city of London was determined by the laws of
00:34:59.740 physics but if you want to understand why the city of London was created that's
00:35:04.840 a wrong level of analysis trying to say well the laws of physics mandated that
00:35:09.320 London would be there eventually doesn't tell you much about the reasons why
00:35:12.520 London actually happened it just says that London doesn't obey supernatural
00:35:19.480 laws it obeys physical laws it was determined to be there if you want to
00:35:23.220 really understand why London is there then you'd have to talk about history and
00:35:26.920 politics and wars and cultures and et cetera et cetera in order to get a full
00:35:32.860 understanding as full as we can of why London is there rather than just saying
00:35:37.500 it was determined to be there what's that got to do with this well we're just
00:35:41.460 saying that comprehension we can comprehend stuff we can comprehend stuff we
00:35:46.920 have comprehended stuff that capacity to comprehend was determined by the laws
00:35:52.380 of physics mandated by the laws of physics the rules of physics have allowed
00:35:56.980 for comprehension to exist comprehension of everything that has been
00:36:01.660 comprehended some of which is the laws of physics we've been able to
00:36:05.760 understand the laws of physics the laws of physics as we know them as we
00:36:09.380 understand them. That's been mandated by those laws of physics. Now, you might
00:36:13.300 very well say, well, this process can't go on forever. Now, again, again, go back
00:36:17.060 to what Macaulay said on what principle is it, that with nothing but improvement
00:36:22.580 behind us, we to expect nothing but deterioration before us. And the
00:36:28.260 paraphrase, which I talk from David Deutsch, to be honest. David paraphrased is to
00:36:34.580 say, how is it that with nothing but simplifications and
00:36:38.020 unification behind us, are we expect a wall of are we to expect a wall of
00:36:43.380 complexity and incomprehensibility before us? In other words, the laws of
00:36:48.020 physics hitherto that we have gradually come to discover over time, have
00:36:53.700 always revealed themselves to be comprehensible. Our most complex laws of
00:36:59.060 physics at the moment are comprehensible. This has always been the story, and we
00:37:05.060 have continued to understand the laws of physics. So to say that some
00:37:09.860 law of physics in the future is going to be incomprehensible. This is a
00:37:14.100 strong, this is an argument that is made by so many public intellectuals.
00:37:18.580 Is a belief in the supernatural. It's a belief that there will be something
00:37:23.140 that is mandated to be incomprehensible by those same laws.
00:37:28.900 But the best we know right now, and that's, again, all we can go on is the best
00:37:32.900 that we know right now, is that the laws of physics, as we know them,
00:37:37.380 mandate their own comprehensibility. Because comprehension is a
00:37:42.820 computation. It's something that minds do. The mind, as it comprehend, has
00:37:47.700 comprehended quantum theory and computation. And marrying these things
00:37:54.180 together, all physical processes can be computed by this
00:37:59.220 universal quantum Turing machine, the universal quantum computer.
00:38:03.380 Deutscher's creation of theory of universal quantum computation,
00:38:10.340 that such a quantum computer can simulate the operation of
00:38:14.500 any other physical system in the entire universe, including a brain.
00:38:18.820 Which can comprehend the laws of physics? Which themselves are comprehensible
00:38:23.460 by that brain? And so therefore, the laws of physics
00:38:26.740 that allowed for brains to come to comprehend things,
00:38:30.100 mandate their own comprehensibility. So this is an important aspect of human
00:38:34.980 nature or the question of what a person is. A person is an entity
00:38:39.540 able to complete computations. A person is made possible by the fact that the laws
00:38:43.940 of physics are computable. But more than this fact,
00:38:46.500 a person is able to create explanations of the rest of physical reality.
00:38:50.580 We have then a confluence of two of the deepest strands in the fabric of reality.
00:38:56.100 The theory of computation and the theory of epistemology.
00:38:59.060 A person is to be found at the crossroads of these. Their brain is a computer
00:39:06.260 that is able to generate explanations. It is a unique kind of computer.
00:39:10.900 The hardware is universal, a small ask after all, for all we needed
00:39:14.580 was paper and the ability to read some symbols. And our brain can do that and
00:39:20.900 It can comprehend what is comprehensible. And the laws of physics are
00:39:24.500 comprehensible. And it manages this by conjecturing,
00:39:27.460 guessing what might be so. And then criticizing via a method of comparing that
00:39:32.100 guess to physical reality. It tests the guess. And so over time, the mind
00:39:36.980 comes to represent the rest of physical reality to increasing accuracy
00:39:40.980 over time as it learns more. How did the brain and mind come into being?
00:39:46.020 By that other deep thread of the fabric of reality,
00:39:49.380 evolution by natural selection. Now we did not know why it is
00:39:53.380 that blind evolution seems to have tended towards
00:39:57.380 increasing complexity. It seems to have wandered seemingly aimlessly
00:40:02.020 towards complexity. After all, for the overwhelming majority of the history of life
00:40:06.660 on earth, very little was done with DNA. For billions of years,
00:40:10.900 nothing more complex than bacteria multiplied in the oceans and on the land.
00:40:15.060 But then an explosion of complexity did happen and more than once.
00:40:19.700 Ultimately, the emergent and yet fundamental principles of evolution by natural
00:40:27.060 creativity surviving. And this then allowed for memes to be not only encoded in
00:40:32.020 the minds of people, but allowed for a process of evolution
00:40:35.620 of those memes. A variety of memes that make a person a person,
00:40:39.380 both rational, irrational and anti-rational. But importantly,
00:40:42.820 the rational memes, those memes that allow for fast error correction of ideas
00:40:46.740 and thus objective improvement of the knowledge of their holders
00:40:49.860 has evolved. A human person then has evolved via a process of
00:40:53.940 near Darwinian selection. And then that person has a mind which
00:40:57.460 contains memes subject to the selective pressure of criticism
00:41:01.380 so that some memes do not survive. And new ideas can be created.
00:41:05.540 We people therefore find ourselves at the junction now of three threads,
00:41:09.940 evolution by natural selection, the theory of computation and universal
00:41:13.540 computation of that, and the theory of knowledge, the capacity for universal
00:41:17.940 explanation by the means of conjecture and refutation.
00:41:21.140 But people persist over time while also in a constant state of change
00:41:25.620 as the ancient Greek philosopher Peraclitus said in around 500 BCE,
00:41:31.380 no man ever steps in the same river twice, for it is not the same river
00:41:35.540 and he is not the same man. But he is, is he not?
00:41:39.540 Were he not? No one would ever be responsible for anything.
00:41:43.140 Are we constantly changing? Yes, so we are not the same person as we were a moment ago,
00:41:48.180 but if we are responsible then something must persist over time to say that
00:41:52.580 we are the same person who stole the loaf of bread or told the lie yesterday.
00:41:56.740 Here we get into questions of continuous change, time and constants.
00:42:00.980 Something does indeed remain the same about a person from moment to moment.
00:42:04.660 That creative software running on the hardware that is the brain
00:42:07.700 is a constant from moment to moment. Our capacity to explain the world around us
00:42:12.180 does not change. In some deep sense it is who we are.
00:42:16.340 In or out of the river this is a constant while much else might change
00:42:20.660 the atoms in our bodies and the memories and ideas we have.
00:42:24.100 That remains the same. That is the defining characteristic for person
00:42:27.940 and in that sense we are all of us unchanging in a sense
00:42:31.620 and all of us the same. As that program that is our mind searches for new
00:42:35.700 explanations and answers it does so because it, we all of us
00:42:42.820 As Popper said there may be great differences between us with regard to
00:42:49.540 yet we are all equal in our infinite ignorance.
00:42:57.460 Certainly we are in part our memories the ideas we have that motivate our
00:43:01.780 behaviours. We are where we direct our attention that innate capacity to
00:43:06.180 explain, ponder, consider and reflect. We are responsible for where we
00:43:10.580 turn that attention and if we learn the lesson of the importance of
00:43:14.020 quiet reflection then we are responsible for those occasions when we do
00:43:17.780 not. We are constant in our capacity to explain.
00:43:21.540 We are constantly changing in the ideas that we have.
00:43:24.660 Are we more to be identified with our ideas at any one time
00:43:28.980 or are more fundamental nature of being able to generate ideas in the first
00:43:33.220 place? We are unavoidably both our ideas and the capacity to generate them.
00:43:38.900 We are both the same as we step into and out of the river
00:43:42.180 and yet different. This is not a great contradiction.
00:43:45.380 For the final strand, quantum theory, tells us all physical objects in the
00:43:50.100 universe exist in a multiverse and this means a person at this
00:43:54.100 instant is actually uncountably infinite, fungible, entirely identical
00:43:58.740 instances of oneself like an electron. An electron at any one place,
00:44:04.420 at any one time, consists of infinitely many, uncountably infinitely
00:44:09.220 many, fungible, entirely identical instances of itself.
00:44:13.460 All identical ideas, except that in a moment some measure of those
00:44:17.540 electrons will do different things. They will go left rather than right
00:44:21.540 and so then the original infinite number of electrons will partition or
00:44:27.380 Both are infinite so the total number has not changed
00:44:30.340 and nor is any group of those, the original or the two groups it splits into,
00:44:34.820 different in number. They are, after all, infinite in size.
00:44:39.620 The same is true of a person. A person, as they sit there and listen to this,
00:44:43.620 is actually a multiverse object. You are not a single person in a single
00:44:47.940 universe. You are uncountably infinite, many instances,
00:44:52.740 all identical. But for any choice or indeed any quantum event,
00:44:57.060 you will differentiate into groups. Each group will still contain
00:45:00.660 uncountably infinite instances. If there are two groups,
00:45:04.420 then there will be one group of infinite, fungible instances doing one thing
00:45:08.180 and another group doing something else. But you, as a matter of fact,
00:45:12.340 are not one single instance but many. All those fungible instances
00:45:17.300 have the same memory and are conjicturing the same ideas until
00:45:21.460 they don't. And it is then that the conscious experience
00:45:24.500 differentiates too. You are conscious only ever of one set of
00:45:28.340 infinite, fungible instances. Your copies, doing something else,
00:45:32.420 they are conscious of something else. So you are not them.
00:45:35.860 Quantum theory tells us something deep about the nature of personhood.
00:45:39.140 People are more than what we think or what we can observe as a matter of
00:45:42.260 introspection. We too are multiversal and we have evolved such that we can
00:45:47.940 generate knowledge about this multiverse and knowledge tends to cause
00:45:51.460 itself to get replicated to remain instantiated once it is created.
00:45:56.100 We are forming about us knowledge of how to remain in existence
00:45:59.940 in the multiverse. We are knowledge is thus connected to the multiverse
00:46:04.100 because the measure of universes in which knowledge is created
00:46:07.220 tends to increase. Knowledge causes itself to remain instantiated in physical
00:46:12.100 reality. That is its nature. And it is our nature to create it.
00:46:16.020 We are striving to remain in existence. We are people.
00:46:20.100 We are gradually gaining a high fidelity understanding
00:46:23.380 of all the rest of it. And all the rest of it has come together to bring us
00:46:27.540 into being a person is at the nexus of all the strands
00:46:32.100 in the fabric of reality. Now there is something lurking here
00:46:37.380 in understanding the mind as a computation of a kind.
00:46:44.660 It is the case that the brain is hardware. And on this hardware runs the
00:46:49.700 software which I refer to as the mind, which many people refer to as the
00:46:54.020 mind. However, we can't be identified with the software.
00:46:59.460 The software, after all, can be instantiated in any number of physical forms.
00:47:05.540 So if we knew what the code was, so to speak, for a human mind,
00:47:11.940 we could write it down on a piece of paper. But that would not be a person.
00:47:17.940 And the reason it would not be a person is because
00:47:20.900 it's not doing anything. If we take the disk, the compact disk or the
00:47:26.020 DVD or at least days, of course, it's kept in the cloud somewhere. But in the
00:47:29.780 old days, we used to be able to have a disk which contained
00:47:33.380 a planet, a power point for windows or keynote for Mac. The piece of software
00:47:39.220 could be stored on a disk. But insofar as it was the software, it
00:47:44.900 wasn't doing anything until you installed the software and ran the software. The
00:47:50.260 software had to be running before it was actually doing anything.
00:47:53.860 So whatever the software is for a person, it has to be
00:47:57.620 running in some way. So the software for a mind has to be
00:48:02.500 instantiated in the brain. That's one thing. But then it also has to be
00:48:07.140 running. It has to actually be operating for it to be
00:48:11.300 a mind which makes things all quite complicated. And this is where we
00:48:17.620 really come up against the very edge of what we know. A human being
00:48:25.220 is software instantiated in neurons. But obviously we're not identical to
00:48:32.820 our neurons. We're something emergent. We're running on those neurons in some
00:48:39.060 way. But we're not the state of those neurons at any particular time
00:48:43.460 either. We're more than that. It has to be the case that
00:48:48.340 that a human being, a person, is abstract in some way. We're not
00:48:56.180 purely physical. We are, as we say, the software. And the software is not
00:49:02.340 purely physical. It's over and above the atoms, the matter in which it is
00:49:06.660 instantiated. In the same way that the numeral for the number five
00:49:12.260 is not identical to the number five. It's a representation of
00:49:16.580 that abstract object five that exists in abstract space in some way. And
00:49:21.380 there are many different instances, there are many different ways of
00:49:23.940 representing that number using different numerals,
00:49:28.660 different symbols. But they're all equivalent to the thing they represent. But
00:49:35.700 That thing that they represent is an abstract object. Not the physical
00:49:39.220 instantiation they're off. So too with a person, a person is an
00:49:44.660 abstraction that is running upon a brain. But it can't be an abstraction
00:49:51.220 in the same way that the number five is an abstraction.
00:49:55.700 After all, the number five exists out there in abstract space.
00:50:00.260 But we don't. We exist here in the physical real world. In theory,
00:50:06.660 our instantiation could be in silicon. It could be in some other kind of
00:50:11.540 media, but at the moment it's in the wetware of the neurons.
00:50:14.740 But it can't be the case that we are to be identified with the neurons,
00:50:19.460 obviously, because of that fact, because we could be
00:50:22.180 instantiated in something else. But we're not equivalent to the
00:50:25.620 abstraction. After all, the abstraction of the number five is an
00:50:30.500 unchanging perfect ontological object. There is no
00:50:34.660 area in it. It is that thing that's out there that we cannot
00:50:38.260 represent except imperfectly in the physical world.
00:50:41.780 But a person doesn't exist out there in abstract space.
00:50:45.620 It doesn't really make any sense, because if it did exist out there in abstract
00:50:48.660 space, then it would have to be a perfect unchanging thing out there in
00:50:52.660 abstract space. This is what Platonism is kind of about, that there are these
00:50:57.540 perfect objects in abstract space that are unchanging.
00:51:04.340 Is it the case that we are the one exception to the rule where we're the
00:51:08.020 perfect abstraction, which nonetheless is able to change over time?
00:51:11.700 I don't know if that makes sense. But we are an abstraction,
00:51:15.780 but not an abstraction in the sense that the number five is an abstraction,
00:51:19.300 or any other kind of abstraction is an abstraction,
00:51:21.700 because other abstractions are platonic ideals.
00:51:25.220 And those platonic ideals are unchanging, but we change over time.
00:51:30.100 As well as remain constant in certain ways, this constant idea of being able to
00:51:36.020 create explanations is the one constant we carry through
00:51:39.140 from the moment of our becoming people through to our death.
00:51:43.460 We are generating explanations over time. We're conscious of the physical
00:51:47.140 reality in which we exist. But we also, by virtue of the fact we are
00:51:53.300 generating these explanations, changing our minds,
00:51:57.540 creating new ideas in our minds. Those ideas themselves are also
00:52:01.460 abstractions, abstractions that are being instantiated in our minds in
00:52:05.860 various ways. So a person is this very unusual blend between
00:52:11.940 perhaps different from physical things and abstract things.
00:52:16.500 Perhaps it's a third kind of thing. This weird interplay between
00:52:20.660 the physical and the abstract, because as we are running,
00:52:25.700 as we are this mind on this brain that's running, the software that's running on
00:52:32.260 the particular physical instantiation we have at the moment, namely
00:52:35.620 our neurons, or the particular state we have at any one moment in time.
00:52:40.020 After all, we were the same person yesterday and they will be the same person
00:52:43.700 tomorrow, modular minor changes. But the person itself remains the same in
00:52:48.740 some ways, despite the fact they're changing as well.
00:52:51.860 We're abstract, but we're not abstract in the same way that platonic
00:52:55.860 ideals are abstract. So this is where we are really reaching the limits
00:53:00.340 of what we understand a person to be. And this is a very interesting area
00:53:04.260 for people to research. I must credit David Deutsch with some
00:53:09.860 brief but private conversations I had with him when I'm
00:53:12.100 precisely this topic and he inspired me to think along these lines and
00:53:16.340 to continue to think along these lines about what the nature of a person
00:53:22.580 really is. Oh, when I say really is, what a better understanding, a better
00:53:27.220 explanation of what a person is. We don't have much of one yet, but we know it
00:53:32.100 comes in the nexus of these things that I've talked about.
00:53:39.380 but us, as people, existing as minds, running on brains,
00:53:44.420 come to be, come to be these abstract things that seem to need a physical
00:53:49.300 instantiation of a kind, which is a thing that allows for us
00:53:59.140 Now, there is another way in which physics comes to bear on personhood.
00:54:03.860 And I think it illustrates a deep way in which we are both the same person
00:54:07.780 as we step into the river a second time and yet also different.
00:54:12.100 And this is where we consider the nature of personhood
00:54:15.460 in the context of the multiverse understanding of quantum theory.
00:54:20.260 In a particular David Deutsch's invocation of the
00:54:24.500 term fungibility. Right now, as each of us occupy a place at a particular
00:54:30.180 time according to the classical picture that physics gives us,
00:54:33.940 we are, in truth, uncountably many fungible copies of ourselves.
00:54:40.020 David Deutsch's chapter on the multiverse explains more about this.
00:54:43.860 And my series on the multiverse, which is part of the beginning of infinity
00:54:51.700 We have hitherto always understood that to be a person,
00:54:55.860 much like to be a book on a shelf, is to be a single object,
00:55:00.500 occupying a single place at a single time in a single universe.
00:55:05.460 But quantum theory, the most modern variant of quantum theory being the
00:55:09.460 multiverse and the most modern variant of that,
00:55:18.500 There is not one electron there in that place, but infinitely many
00:55:22.500 fungible instances all in the same place at the same time,
00:55:27.300 but occupying different universes and which at some point in the future
00:55:31.300 will partition themselves into measures, different groups,
00:55:38.340 So too with the book on the shelf and so too with a person.
00:55:46.500 you extend across the multiverse. You too are a multiverse object.
00:55:52.260 You have a singular conscious experience, but that experience
00:56:01.700 whether by your conscious choice or the quantum action of an event
00:56:07.860 those instances differentiate. You differentiate in a sense,
00:56:12.740 but you remain only ever conscious of one measure of those instances,
00:56:19.940 those other copies different to you and you form a continuum
00:56:30.820 from you through to instances of you that are doing something completely
00:56:38.420 or bumping into a stranger who will turn out to be a lifelong friend
00:56:41.860 or being interrupted by a call that gives you the opportunity you have been
00:56:45.140 waiting for and there remains you still listening to this
00:56:50.100 that is still infinitely many fungible, perfectly identical copies.
00:56:58.500 constantly in a state of flux, but at the same time your conscious experience
00:57:03.060 remaining singularly about the experience of only one measure of instances,
00:57:08.820 while the other instances are conscious of something else.
00:57:12.420 It is they who do not step back into the river, but you do.
00:57:16.500 And you are the same in that sense. They are different.
00:57:19.780 And yet you are different too because your memory is
00:57:30.420 copies of yourself that are not you. And you are not conscious
00:57:34.180 of going to do otherwise. And you doing what you do,
00:57:38.500 your consciousness being the constant, and though what it is conscious of,
00:57:43.140 all the different times and spaces will continue to change,
00:57:47.460 but you will remain in lockstep with all those other
00:57:51.060 uncountable, fungible instances of yourself, those fungible instances
00:57:55.700 that are you, as could be seen if you had some access to a god's eye view of
00:58:01.060 the multiverse, you would see you as uncountably
00:58:05.460 infinite, fungible instances of yourself in the same place at the same time,
00:58:10.660 but differentiating over time. This is a remarkable fact about what a person is
00:58:19.220 which can compute explanations and comprehend them.
00:58:24.500 explanations which then give them choices so that fungible instances of
00:58:28.580 themselves differentiate into different measures,
00:58:32.020 some larger or some smaller, depending on the personality of that person.
00:58:36.420 Those more like you, of greater measure, those unlike you,
00:58:40.340 of smaller measure. And so not really you at all, but
00:58:43.700 as long as they remain conscious able to create new
00:58:46.500 explanations, which give them choices about what to do next.
00:58:50.420 We are the nexus of the threads of the fabric of reality,
00:58:58.820 unraveling and becoming more entwined over time,
00:59:05.540 but which we now have a scientific and philosophic glimpse
