00:00:07.920 This is a parsimonious way of saying, reality is known to exist, or even, I know, reality
00:00:16.520 That there exists a world external to anyone's thoughts on the matter, should not be
00:00:21.120 a strikingly profound claim to make, and yet generations of philosophers have allowed the
00:00:26.840 misconception to leak into academia, down into the schooling system, so that now we have
00:00:36.720 Not skepticism of the, I don't think, ghosts are real kind, but skepticism of the ancient
00:00:44.080 The concern that we cannot know, and because we cannot know, perhaps almost anything
00:00:49.600 goes, including that nothing exists, or that nothing really truly exists if you like.
00:00:56.400 Let us move beyond the relativists who might claim that there is no external reality, or
00:01:01.720 at least that we cannot make objective claims about it, and let us leave behind the philosophical
00:01:11.880 Here we might even throw the, it's all a simulation idea into the same bin.
00:01:16.960 For there, although there might be an external reality, we cannot know it because we are trapped
00:01:21.920 like Plato's caveman in a world that might bear no resemblance to what we think about it.
00:01:30.200 The idea that not only does an external reality exist outside our minds, but that our minds
00:01:39.160 Computers that explain the world around us with increasing fidelity, minds.
00:01:44.880 The minds of people come to form models, accurate working models in the words of David
00:01:56.440 In one of his TED talks, David speaks about quasars, basically black holes that are literally
00:02:02.200 consuming entire stars, and in the process, creating huge so-called accretion disks, white
00:02:08.720 hot rotating disks of electrically charged matter spinning so fast that intense magnetic
00:02:14.120 fields are generated that cause jets of material to shoot outwards from the disk, making
00:02:18.600 the quasar brighter than an entire galaxy, despite the fact, in terms of their physical
00:02:26.280 The physics, as David, are such an object is so different from that of a human brain,
00:02:31.160 and yet the latter is able to form an accurate explanation, a predictive model and a physical
00:02:39.680 This is astounding, and it is this that allows us to say quasars exist.
00:02:50.320 I think exists if it features unavoidably in our best explanations, but not otherwise.
00:02:56.800 We know quasars exist precisely because we have an explanation of otherwise problematic observations.
00:03:03.200 If we did not have those observations, then we would not have a chain of causation which
00:03:08.160 led both creatively and logically to that object I just described.
00:03:13.400 No explanation of the physical world out there requires that elves exist or magical wizards.
00:03:19.840 But explanations of what happens in Tolkien's The Lord of the Rings do, the book The Lord
00:03:24.480 of the Rings exists, and that book, being a work of fiction, relies upon the existence
00:03:29.640 of elves and magical wizards for its own internal consistency.
00:03:33.920 Those fictional entities exist within a fictional world, but they do not really exist,
00:03:39.560 which is to say they did not exist outside of fictional worlds.
00:03:43.800 No explanation of our physical reality requires us to postulate wizards and elves, so wizards
00:03:57.000 Gravity exists, just like matter exists, and space exists.
00:04:01.600 But saying matter exists tells us very little about its nature.
00:04:05.720 Is it continuously divisible, or is it terminated as smallest possible particle?
00:04:15.000 Atons sure, but they are emergent, they are more complex arrangements of more fundamental
00:04:20.000 particles, protons, neutrons, and electrons, and even some of those are likewise emergent,
00:04:25.280 more complex objects composed of simpler ones, but never mind matter.
00:04:32.720 Is that thing which we must invoke in our explanations of, say, tides or the motion of
00:04:38.480 So indeed, the frustration of a dropped glass smashing upon the floor rather than hovering
00:04:48.480 It used to be thought there was a force of gravity.
00:04:51.640 The force explanation of gravity was a way of understanding gravity as being the attraction
00:05:00.960 On this view, which is the view created by Isaac Newton, and which survived for centuries,
00:05:06.520 the force of attraction could be calculated, and thus many phenomena accurately predicted.
00:05:16.200 They merely knew it was a force, so they were right to say, at the time, when there was
00:05:22.800 no viable alternative, the force of gravity exists.
00:05:26.760 Now if we understand them properly, in light of how we understand knowledge today, we
00:05:31.600 should understand that statement to mean, we've fallibley know that the force of gravity
00:05:37.240 Either that force exists or it does not, there is no middle ground.
00:05:43.960 Our knowledge, everyone's knowledge, at all times we should expect is filled with errors,
00:05:49.400 but it becomes terribly cumbersome to preface everything we say on such topics with, we
00:05:56.600 So we can dispense with that, because it literally goes without saying, so we just say,
00:06:03.520 But we can always be wrong about that, and we should expect to be, and as it turns out,
00:06:10.920 Because now we know better, there were indeed problems found with Newton's theory, there
00:06:19.240 An entirely new theory, Einstein's theory of general relativity, was able to make more
00:06:27.160 And more than this, it postulated the existence of a whole slew of other phenomena and
00:06:35.480 And part of this explanation was that the so-called force of gravity was found not to exist.
00:06:46.720 But it's true nature does not require us to invoke a force of attraction.
00:06:51.560 Cities with mass do not attract one another, they may appear to, but then water poured
00:06:57.040 from a kettle into a cup appears for all the world to flow like a continuous fluid, rather
00:07:02.160 than as discrete little particles more resembling dry sand being poured from a bucket.
00:07:07.760 We know those molecules of H2O exist, even though we cannot see them.
00:07:12.640 Our ability to see them, moment to moment, has no bearing on their existence or otherwise,
00:07:17.640 their existence is invoked because our best theory tells us they exist, and that water
00:07:22.760 as a continuous fluid, which is to say fluid made of stuff which never terminates at a
00:07:30.440 And in the same way, our best current theory decides between two mutually exclusive claims.
00:07:38.240 Gravity is a force, versus gravity is not a force.
00:07:42.360 And gravity is not a force, but attraction you think you feel is an illusion, much like
00:07:47.280 the water is a continuous fluid as an illusion, compelling sure, but your senses deceive
00:07:53.760 If you are able to fall freely, perhaps you've been skydiving, you will feel no attraction
00:07:59.200 Sure if you open your eyes, you will see the ground rushing up to meet you, apparently.
00:08:03.040 But close your eyes, you will feel the wind rush past sure, but that sensation is no
00:08:07.960 clue about anything attracting you, you will not feel a pull, instead you will, literally
00:08:13.840 feel whiteless, if anything, in this non-ideal situation, you will feel pushed somewhat upwards.
00:08:20.880 Many more of us have had this sensation to a much lesser effect in certain kinds of
00:08:25.640 fun park rides that give you a couple of seconds of freefall before bringing you to a very
00:08:32.200 In those moments, I have never noticed attraction to the earth, and I've looked for it.
00:08:37.120 I have felt in truth, attraction to nothing at all.
00:08:40.560 And if anything is slight force upwards, and that of course is the force of air upon me
00:08:46.760 This force, the supposed attraction, a pulling force, just is not there.
00:08:51.960 We know what a pull is, any friend can pull your arm, and you will notice what it is
00:08:55.200 like to accelerate towards them, but not in freefall.
00:08:58.960 You can be disabused by the illusion of the sensation of the force of gravity by experiment
00:09:05.040 What gravity actually does, is to sort space and time, or better yet, the single space
00:09:11.600 This means that when objects move, that are not moved through, a Euclidean space of sharp
00:09:16.520 angles along idealised lines such as in high school geometry textbooks.
00:09:21.280 But does all of this mean that the force of gravity simply winked out of existence,
00:09:25.960 the day Einstein published his theory of general relativity?
00:09:31.840 But were the people prior to this date right to say it existed?
00:09:35.480 Yes, they were right to say it existed, but they were wrong.
00:09:41.360 They could not possibly predict the content of future theories.
00:09:45.000 So we are right today to say the force of gravity does not exist, but does it really
00:09:51.120 Yes, and if you want to say more, you can say it does not exist according to our best
00:09:59.880 Yes, it really does not exist according to our best explanation, but someone might
00:10:05.640 But maybe it really, really like ultimately in the final analysis, there really is a force
00:10:11.200 of gravity, but there can be no final analysis.
00:10:15.200 It's just constant progress and improvement, but then you don't really know if the force
00:10:24.240 To really know something means to really know it.
00:10:28.120 And that means according to our best theory and fallibly at that, and knowing that the theory
00:10:33.080 is going to contain errors, not yet found, when someone wants the really, really true
00:10:38.680 knowledge, they are appealing to a feeling of certainty and finality and infallibility.
00:10:44.960 They are demanding a standard, no human can ever reach.
00:10:48.400 Aha, they say, but doesn't this mean we can never really truly know anything?
00:10:58.680 I know it, but you have to give up the notion that no means have the final once and
00:11:04.800 for all completely perfect and error-free answer.
00:11:09.480 Yes, in the final once and for all completely perfect and error-free account of things does
00:11:22.400 I really truly do, but what you're after is not knowledge apparently.
00:11:27.640 You don't want to say, I know about gravity, you want to say, you're certain about it.
00:11:32.680 You want to be an omniscient god or an oracle, you want to appeal to the supernatural.
00:11:38.200 Now there are many such things we could have put into this category, flogiston, the substance
00:11:42.400 that made the difference between that which was flammable and that which was not.
00:11:50.760 A real and vital, the life force that animated living things, or the luminiferous ether,
00:11:56.400 the substance permeating all of space which vibrated with the passage of light waves, and
00:12:04.480 At times we will be mistaken about what exists, but all we can say about what exists is
00:12:10.280 what our best theories say, and nothing more, nothing less.
00:12:14.920 But beyond our knowledge, of course, there are more things than we know to exist.
00:12:19.520 That will always be so, and some of what we think exists will be mistaken.
00:12:28.520 It is, as I like to say, the distinction between that somewhat antiquated way of thinking
00:12:32.560 about philosophy, the ontology of the world, which is to say what ultimately reality consists
00:12:38.560 of utterly independent of people coming to explain it, and epistemology, what we know
00:12:49.920 Knowledge is by its nature, conjectural, and so will contain errors.
00:12:54.080 The only other hand is the flawless account of the perfect reality, so knowledge of ontology
00:12:59.360 is something like an imperfect, perfect account, a silly and pointless notion.
00:13:04.920 That reality exists, and we can come to some understanding of it, is quite enough.
00:13:10.640 That how knowledge is by itself imperfect, and always at every moment riddled with errors,
00:13:16.080 is a product of the process that produces it, our minds, our fallible minds.
00:13:21.440 And this is a cause for hope and genuine excitement, for it means that we will have before
00:13:25.200 us a continuous stream of evidence, which we can interpret, allowing us to correct the errors
00:13:31.040 in our guesses about what the nature of reality is.
00:13:34.520 We can improve and make things ever better if we choose to.
00:13:37.880 We may er and falter, indeed we will, but this is just to say that we will never get
00:13:42.240 to a point beyond which progress cannot be made.
00:13:45.920 For if that were possible, then hope would indeed be lost, would be at the end, would
00:13:50.160 have found an answer that could not be improved, progress would come to a screeching halt,
00:13:55.520 stasis would follow, and that would be a kind of hell, a perpetual state of nothing
00:14:00.080 changing, and the gradual realisation that this is it.
00:14:04.320 Where the only novel to be found, in looking back to the past, to a time where it was
00:14:08.560 possible for things to actually get better, but happily we will not reach the end, there
00:14:13.400 is no end to what we shall discover, and what we will find exists tomorrow, like everything
00:14:19.160 What we know to exist is perpetually open to revision, and this allows us, however slowly
00:14:24.320 and incrementally, to gain control of it, and to show how its existence can help solve
00:14:29.520 our problems, and to make us all the better for having found it.