WEBVTT 00:00:00.000 --> 00:00:01.639 All right, I want you to just, for a second, 00:00:01.780 --> 00:00:04.660 picture a scene with me. Okay. It's November. 00:00:05.759 --> 00:00:10.759 The year is 1717, and it is a biting, freezing 00:00:10.759 --> 00:00:13.679 cold night in Paris. Mm -hmm. But I don't want 00:00:13.679 --> 00:00:15.279 you to think of the, you know, the romantic, 00:00:15.380 --> 00:00:17.800 glowing Paris we see in movies. Right. This is 00:00:17.800 --> 00:00:20.039 not the city of light yet, not by a long shot. 00:00:20.199 --> 00:00:23.640 Exactly. This is 18th century Paris. It's dark. 00:00:23.820 --> 00:00:26.469 It probably smells of wood smoke and... Well, 00:00:26.550 --> 00:00:29.910 open sewers. It's quiet except for the wind rattling 00:00:29.910 --> 00:00:32.250 the shutters. It's a setting that sounds like 00:00:32.250 --> 00:00:34.289 the beginning of, I don't know, a Charles Dickens 00:00:34.289 --> 00:00:36.369 novel, doesn't it? It really does. Yeah. Because 00:00:36.369 --> 00:00:39.130 we're zooming in on a very specific place. The 00:00:39.130 --> 00:00:41.770 steps of a church. Saint -Jean -Laurent. Okay. 00:00:41.850 --> 00:00:44.829 And right there, on those cold stone steps exposed 00:00:44.829 --> 00:00:47.969 to all the elements, someone has left a bundle. 00:00:48.229 --> 00:00:52.119 No! It's a newborn baby. A foundling. Foundling. 00:00:52.240 --> 00:00:54.159 And we have to be really honest about the reality 00:00:54.159 --> 00:00:56.880 of that time. Abandoning a child on church steps 00:00:56.880 --> 00:00:58.880 in November was, I mean, it was usually a death 00:00:58.880 --> 00:01:01.399 sentence. A death sentence. Oh, absolutely. The 00:01:01.399 --> 00:01:04.500 survival rate for foundlings in 18th century 00:01:04.500 --> 00:01:07.219 France was terrifyingly low. You're talking about 00:01:07.219 --> 00:01:10.400 the cold, hunger, disease. The odds were just 00:01:10.400 --> 00:01:12.920 stacked entirely against this child. So by all 00:01:12.920 --> 00:01:14.719 rights, that should have been the end of the 00:01:14.719 --> 00:01:17.879 story. Just a tragic anonymous statistic in the 00:01:17.879 --> 00:01:20.230 parish. Should have been. But it wasn't. This 00:01:20.230 --> 00:01:22.430 shivering infant didn't just survive the night. 00:01:22.650 --> 00:01:24.849 He grew up to become one of the most formidable 00:01:24.849 --> 00:01:26.989 intellects of the entire Enlightenment. It's 00:01:26.989 --> 00:01:28.909 an incredible story. We were talking about a 00:01:28.909 --> 00:01:32.810 man who would basically rewrite the laws of physics, 00:01:32.969 --> 00:01:35.409 co -edit the most important, maybe the most famous 00:01:35.409 --> 00:01:39.439 book in human history. And he tried to turn music 00:01:39.439 --> 00:01:41.480 into a math problem. And maybe the most surprising 00:01:41.480 --> 00:01:43.900 thing of all, a man who had the integrity, or 00:01:43.900 --> 00:01:46.599 maybe it was the skepticism, to tell a king he 00:01:46.599 --> 00:01:49.040 didn't want a planet or a moon named after him. 00:01:49.079 --> 00:01:51.519 Today we are diving deep into the life and mind 00:01:51.519 --> 00:01:53.959 of Jean -Laurent d 'Alembert. A true polymath. 00:01:54.079 --> 00:01:55.959 I mean, he was a mathematician, a physicist, 00:01:56.200 --> 00:01:59.260 a philosopher, a music theorist, and a central 00:01:59.260 --> 00:02:02.040 figure in what they called the Republic of Letters. 00:02:02.159 --> 00:02:05.420 This deep dive is going to be a wild ride. We've 00:02:05.420 --> 00:02:08.599 got a massive stack of sources here, biographies, 00:02:08.680 --> 00:02:11.360 his own articles from the encyclopedia, historical 00:02:11.360 --> 00:02:14.750 analyses of his physics, and even some... pretty 00:02:14.750 --> 00:02:17.889 juicy letters from the salons of Paris. Our mission 00:02:17.889 --> 00:02:20.750 today is to really unpack how this abandoned 00:02:20.750 --> 00:02:24.569 child rose to the absolute top of European intellectual 00:02:24.569 --> 00:02:28.810 society. We need to understand his massive contributions 00:02:28.810 --> 00:02:31.889 to science because, spoiler alert, if you're 00:02:31.889 --> 00:02:33.729 an engineer or a physicist listening to this 00:02:33.729 --> 00:02:36.750 today, you are using his math. Absolutely. We're 00:02:36.750 --> 00:02:39.169 going to have to look at the trite, the dynamique, 00:02:39.330 --> 00:02:41.310 the wave equation. I mean, these are things that 00:02:41.310 --> 00:02:43.430 genuinely revolutionized how we understand the 00:02:43.430 --> 00:02:45.139 physical. world. But I also want to get into 00:02:45.139 --> 00:02:46.780 the messy stuff. Oh, there's always messy stuff. 00:02:46.900 --> 00:02:49.379 For a guy who is a genius of logic, he had some 00:02:49.379 --> 00:02:51.539 serious blind spots. We're going to talk about 00:02:51.539 --> 00:02:53.780 his feud with the most famous musician of the 00:02:53.780 --> 00:02:56.599 era. And we absolutely have to talk about the 00:02:56.599 --> 00:02:58.460 gambler's fallacy. Oh, the Dallin Bear system. 00:02:58.680 --> 00:03:01.240 It's a classic. It's basically the reason casinos 00:03:01.240 --> 00:03:03.500 make so much money. It proves that even the most 00:03:03.500 --> 00:03:06.539 brilliant minds can get tripped up by, you know, 00:03:06.560 --> 00:03:08.620 simple probability. I feel like that's going 00:03:08.620 --> 00:03:10.419 to make me feel a lot better about my own struggles 00:03:10.419 --> 00:03:13.979 with math. Fair enough. So let's go back to the 00:03:13.979 --> 00:03:16.960 beginning. The church steps. Saint -Jean -Laurent, 00:03:17.020 --> 00:03:19.919 who leaves a baby on a church step in November. 00:03:20.599 --> 00:03:22.580 Do we even know who the parents were? We do. 00:03:22.699 --> 00:03:24.759 And this is where the story immediately takes 00:03:24.759 --> 00:03:28.219 a very sharp turn away from that sort of poverty 00:03:28.219 --> 00:03:30.719 -stricken orphan narrative you might be picturing. 00:03:30.819 --> 00:03:34.139 Okay. This wasn't a case of a poor family who 00:03:34.139 --> 00:03:36.860 couldn't afford to feed another mouth. The mother 00:03:36.860 --> 00:03:39.939 was Claudine Guérin de Tencin. Wait, hang on. 00:03:39.939 --> 00:03:43.479 I've heard that name. The Tencin. As in the famous 00:03:43.479 --> 00:03:46.879 writer and salon hostess. The very same. She 00:03:46.879 --> 00:03:49.580 was an absolute force of nature in Parisian society. 00:03:49.840 --> 00:03:52.500 She was a runaway nun who turned her home into 00:03:52.500 --> 00:03:55.060 one of the most influential salons in Europe. 00:03:55.219 --> 00:03:57.719 She was incredibly well connected. She was wealthy, 00:03:57.819 --> 00:04:02.139 prominent. But she wasn't married. Exactly. In 00:04:02.139 --> 00:04:05.120 1717, for a woman of her high social standing 00:04:05.120 --> 00:04:07.900 to have an illegitimate child. It would have 00:04:07.900 --> 00:04:09.879 been a catastrophic scandal. I mean, it would 00:04:09.879 --> 00:04:11.979 have just ruined her reputation, her position, 00:04:12.159 --> 00:04:14.680 everything. So she made a calculation. A very 00:04:14.680 --> 00:04:17.000 cold calculation. She abandoned the child to 00:04:17.000 --> 00:04:20.060 save her status. That is just, it's brutal. So 00:04:20.060 --> 00:04:22.139 she leaves him there, assuming he'll be picked 00:04:22.139 --> 00:04:24.879 up by the church. Well, let's not think about 00:04:24.879 --> 00:04:27.120 the alternative. No. What about the father? Was 00:04:27.120 --> 00:04:29.589 he in the picture at all? He was. The father 00:04:29.589 --> 00:04:33.250 was the Chevalier Louis Camus de Touche. He was 00:04:33.250 --> 00:04:36.290 an artillery officer, a military man. But the 00:04:36.290 --> 00:04:38.449 crucial detail here is that he wasn't in Paris 00:04:38.449 --> 00:04:41.149 when the birth happened. He was abroad on booty. 00:04:41.529 --> 00:04:44.149 But, and this is the big twist in the story, 00:04:44.350 --> 00:04:46.990 when he returned to Paris and found out what 00:04:46.990 --> 00:04:50.060 Claudine had done, He didn't just wash his hands 00:04:50.060 --> 00:04:52.379 of it. He actually cared. He did. He went looking 00:04:52.379 --> 00:04:55.480 for the child. He cracked the baby down, probably 00:04:55.480 --> 00:04:57.480 through church records or the foundling hospital 00:04:57.480 --> 00:04:59.480 where the baby had been taken after being found. 00:04:59.560 --> 00:05:02.800 He found his son. So, happy ending then. He takes 00:05:02.800 --> 00:05:05.399 the boy home, raises him as the son of an artillery 00:05:05.399 --> 00:05:07.899 officer. Not quite. You have to remember the 00:05:07.899 --> 00:05:10.600 incredibly rigid social structures of the time. 00:05:11.199 --> 00:05:14.399 Detouche was a chevalier, a nobleman. He couldn't 00:05:14.399 --> 00:05:16.779 just bring an illegitimate child into his household 00:05:16.779 --> 00:05:19.000 and raise him as his heir. The stigma was just 00:05:19.000 --> 00:05:21.819 too strong. So what did he do? He orchestrated 00:05:21.819 --> 00:05:25.079 the solution. He arranged for the boy who, by 00:05:25.079 --> 00:05:27.759 the way, had been named Jean Laurent after the 00:05:27.759 --> 00:05:29.500 patron saint of the church where he was found 00:05:29.500 --> 00:05:32.139 to be fostered. Fostered by whom? Someone in 00:05:32.139 --> 00:05:34.120 his circle? Not at all. He placed him with a 00:05:34.120 --> 00:05:36.420 woman named Madame Rousseau. And it's an important 00:05:36.420 --> 00:05:39.399 note. There is no relation to the famous philosopher 00:05:39.399 --> 00:05:41.639 Jean -Jacques Rousseau. Okay, got it. So who 00:05:41.639 --> 00:05:44.339 was this Madame Rousseau? She was the wife of 00:05:44.339 --> 00:05:47.379 a glazier. A glassworker. A glazier. So we're 00:05:47.379 --> 00:05:50.519 talking working class. Very much so. A humble, 00:05:50.680 --> 00:05:54.160 artisan home. And this is the environment where 00:05:54.160 --> 00:05:57.089 d 'Alembert... one of the greatest geniuses of 00:05:57.089 --> 00:05:59.769 the century, would spend the next 50 years of 00:05:59.769 --> 00:06:02.629 his life. Wait, did you just say 50 years? Five 00:06:02.629 --> 00:06:05.149 zero? Rarely 50. He didn't just stay there until 00:06:05.149 --> 00:06:07.389 he was 18 and then leave for college. He lived 00:06:07.389 --> 00:06:09.850 with the glacier and his wife well into his adulthood, 00:06:10.069 --> 00:06:13.050 long after he had become famous. You're telling 00:06:13.050 --> 00:06:15.610 me he was writing for the encyclopedia, corresponding 00:06:15.610 --> 00:06:17.810 with kings and emperors, and still coming home 00:06:17.810 --> 00:06:19.970 to the glacier's house. That's exactly right. 00:06:20.050 --> 00:06:23.110 It's this incredible paradox. That is amazing 00:06:23.110 --> 00:06:25.920 stability for someone who... started life on 00:06:25.920 --> 00:06:29.480 a doorstep yeah but i have to ask about the dynamic 00:06:29.480 --> 00:06:31.860 there you have this brilliant child clearly a 00:06:31.860 --> 00:06:35.379 prodigy living in a working -class home was madame 00:06:35.379 --> 00:06:37.759 rousseau like the supportive mom in a feel -good 00:06:37.759 --> 00:06:41.000 movie you know go get him tiger you're a genius 00:06:42.000 --> 00:06:44.459 Quite the opposite, actually. And this is one 00:06:44.459 --> 00:06:46.600 of those tragic comic elements of D 'Alembert's 00:06:46.600 --> 00:06:49.939 life that I find so fascinating. She was a stable 00:06:49.939 --> 00:06:52.699 mother figure. You know, she fed him and housed 00:06:52.699 --> 00:06:55.519 him. She gave him a home. But she absolutely 00:06:55.519 --> 00:06:58.000 did not get him. She didn't understand his intellect? 00:06:58.220 --> 00:06:59.800 Not in the slightest. She didn't understand his 00:06:59.800 --> 00:07:02.180 ambition, his drive, any of it. Can you give 00:07:02.180 --> 00:07:04.439 me an example? Oh, there's a very famous anecdote 00:07:04.439 --> 00:07:07.560 that historians always cite. Whenever D 'Alembert 00:07:07.560 --> 00:07:09.759 would achieve something, you know, maybe he cracked 00:07:09.759 --> 00:07:12.310 a new mathematical problem or... wrote a brilliant 00:07:12.310 --> 00:07:14.509 paper he would run to her, all excited to share 00:07:14.509 --> 00:07:16.569 his discovery. Like any kid would. And she would 00:07:16.569 --> 00:07:18.509 just look at him, shake her head, and say, you 00:07:18.509 --> 00:07:20.790 will never be anything but a philosopher, and 00:07:20.790 --> 00:07:23.389 what is that but an ass who plagues himself all 00:07:23.389 --> 00:07:25.750 his life that he may be talked about after he 00:07:25.750 --> 00:07:30.170 is dead? An ass who plagues himself. Wow. Thanks 00:07:30.170 --> 00:07:32.490 for the vote of confidence, Mom. That is just 00:07:32.490 --> 00:07:36.110 scathing. It certainly must have kept his ego 00:07:36.110 --> 00:07:38.360 in check. But here's the other side of the coin. 00:07:38.540 --> 00:07:40.680 While he didn't get any intellectual encouragement 00:07:40.680 --> 00:07:43.279 from her, he did have financial support coming 00:07:43.279 --> 00:07:46.959 from the shadows. His biological father, Detutious. 00:07:47.100 --> 00:07:49.800 Right. He never officially recognized him as 00:07:49.800 --> 00:07:52.300 his son, so legally d 'Alembert remained a bastard. 00:07:52.519 --> 00:07:56.040 But Laetitia secretly paid for his entire education. 00:07:56.379 --> 00:07:59.240 He set up an annuity of 1 ,200 livres a year 00:07:59.240 --> 00:08:01.660 for him. Which, in the early 18th century, is 00:08:01.660 --> 00:08:04.079 not pocket change. That's a serious amount of 00:08:04.079 --> 00:08:06.660 money. Oh no, it was enough to secure a top -tier 00:08:06.660 --> 00:08:08.779 education. It's what allowed him to enter the 00:08:08.779 --> 00:08:11.439 Jensenist College des Quatre Nations, also known 00:08:11.439 --> 00:08:13.319 as College Mazere, when he was just 12 years 00:08:13.319 --> 00:08:15.579 old. Okay, so he goes from the glazier's house 00:08:15.579 --> 00:08:19.300 to this... prestigious college but it wasn't 00:08:19.300 --> 00:08:21.019 a science academy or anything like that right 00:08:21.019 --> 00:08:23.459 this was run by jansenists right and this is 00:08:23.459 --> 00:08:25.740 absolutely crucial for understanding d 'alembert's 00:08:25.740 --> 00:08:27.920 intellectual rebellion to understand what he 00:08:27.920 --> 00:08:29.819 fought for you really have to understand what 00:08:29.819 --> 00:08:31.779 he was fighting against and what was that the 00:08:31.779 --> 00:08:34.399 jansenists were a very specific very rigorous 00:08:34.399 --> 00:08:37.519 catholic sect the curriculum was heavy on theology 00:08:37.519 --> 00:08:41.379 philosophy law and the arts but scientifically 00:08:42.509 --> 00:08:44.529 They were still teaching Cartesian principles. 00:08:45.049 --> 00:08:48.009 Cartesian as in Rene Descartes. I think therefore 00:08:48.009 --> 00:08:51.379 I am. Yes. but also Descartes' physics. And this 00:08:51.379 --> 00:08:53.720 is where it gets really sticky. In the early 00:08:53.720 --> 00:08:56.120 18th century, France was still clinging to Descartes' 00:08:56.240 --> 00:08:58.419 ideas about how the universe worked, specifically 00:08:58.419 --> 00:09:01.519 the theory of vortices. Vortices. Vortices in 00:09:01.519 --> 00:09:03.840 space. That's basically the idea. See, Descartes 00:09:03.840 --> 00:09:05.379 couldn't get his head around gravity working 00:09:05.379 --> 00:09:07.799 across empty space. He just hated the idea of 00:09:07.799 --> 00:09:09.500 a force acting at a distance. It seemed like 00:09:09.500 --> 00:09:12.399 magic to him. Okay. So he hypothesized that the 00:09:12.399 --> 00:09:14.419 entire universe was filled with these invisible 00:09:14.419 --> 00:09:17.399 particles swirling around in giant whirlpools 00:09:17.399 --> 00:09:20.309 or vortices. And these swirling particles physically 00:09:20.309 --> 00:09:22.629 pushed the planets around in their orbit. So 00:09:22.629 --> 00:09:24.870 the planets are just like debris caught in a 00:09:24.870 --> 00:09:26.710 cosmic drain. That's a pretty good way to put 00:09:26.710 --> 00:09:29.090 it. Now, by the time d 'Alembert is in school, 00:09:29.429 --> 00:09:31.830 Isaac Newton, over in England, has already published 00:09:31.830 --> 00:09:34.690 his Principia. Newton has the math. He has universal 00:09:34.690 --> 00:09:37.409 gravitation. It actually works. But the French 00:09:37.409 --> 00:09:39.970 schools were stubborn. Incredibly stubborn. It 00:09:39.970 --> 00:09:42.370 was a matter of national pride in a way. So they 00:09:42.370 --> 00:09:45.289 were still teaching Descartes' innate ideas. 00:09:45.809 --> 00:09:48.289 This notion that we are born knowing certain 00:09:48.289 --> 00:09:50.870 truths in these swirling, invisible vortices. 00:09:51.389 --> 00:09:53.750 D 'Alembert being the budding genius that he 00:09:53.750 --> 00:09:56.809 is, he smells a rat. He scorned it. He absolutely 00:09:56.809 --> 00:09:59.750 hated the curriculum. Later in life, he wrote 00:09:59.750 --> 00:10:02.230 about how much he despised that education. He 00:10:02.230 --> 00:10:05.750 called the theology he was forced to study unsubstantial 00:10:05.750 --> 00:10:08.429 fodder. Unsubstantial fodder. I like that. He 00:10:08.429 --> 00:10:10.289 was hungry for something concrete, something 00:10:10.289 --> 00:10:14.190 provable. He wanted mathematical rigor, not swirling 00:10:14.190 --> 00:10:16.529 invisible particles. It's a classic teenage rebellion, 00:10:16.549 --> 00:10:18.769 isn't it? Yeah. But instead of sneaking out to 00:10:18.769 --> 00:10:21.470 drink cheap wine, he's sneaking out to do calculus. 00:10:22.230 --> 00:10:24.700 Essentially, yes. And the funny thing is... The 00:10:24.700 --> 00:10:27.259 Jansenists actually recognized his brilliance. 00:10:27.379 --> 00:10:29.340 They tried to recruit him. They really wanted 00:10:29.340 --> 00:10:31.759 him to become a priest. They pushed him hard 00:10:31.759 --> 00:10:34.840 toward theology. Wow. Imagine D 'Alembert as 00:10:34.840 --> 00:10:36.639 a priest. That would have changed history a little 00:10:36.639 --> 00:10:39.980 bit. He refused flat out. Said it was unsubstantial. 00:10:40.100 --> 00:10:42.750 So then he pivoted. He went to law school for 00:10:42.750 --> 00:10:45.649 a couple of years. He actually became an avocat, 00:10:45.649 --> 00:10:50.289 a lawyer in 1738. But he was bored out of his 00:10:50.289 --> 00:10:53.029 mind. So then he dabbled in medicine for a bit. 00:10:53.190 --> 00:10:55.409 But he said he couldn't handle the imprecision 00:10:55.409 --> 00:10:58.009 of it. It wasn't rigorous enough for him. He 00:10:58.009 --> 00:11:00.830 sounds hard to please. He was. Finally, he just 00:11:00.830 --> 00:11:03.350 couldn't deny it anymore. He fell completely 00:11:03.350 --> 00:11:06.090 in love with mathematics. It was the only thing 00:11:06.090 --> 00:11:08.250 that gave him the absolute certainty that he 00:11:08.250 --> 00:11:10.629 craved. And somewhere during this transition, 00:11:10.750 --> 00:11:12.480 he sort of of invents himself, right? He changes 00:11:12.480 --> 00:11:15.179 his name. Yes. This is when he really forges 00:11:15.179 --> 00:11:17.779 his own identity. He was enrolled in school under 00:11:17.779 --> 00:11:20.419 the name Jean -Baptiste D 'Aremberg. But that 00:11:20.419 --> 00:11:22.659 wasn't quite right. Eventually, he changed it 00:11:22.659 --> 00:11:25.279 to d 'Alembert. Why d 'Alembert? Where did that 00:11:25.279 --> 00:11:28.100 come from? The leading theory is simply euphony. 00:11:28.279 --> 00:11:30.740 It just sounded better. It does have a ring to 00:11:30.740 --> 00:11:33.519 it. Jean -Laurent d 'Alembert. It has a rhythm, 00:11:33.620 --> 00:11:36.480 a certain dignity. It sounds like the name of 00:11:36.480 --> 00:11:38.820 someone who is going to discover a theorem. It 00:11:38.820 --> 00:11:41.399 really does. It sounds distinguished. So, OK, 00:11:41.539 --> 00:11:44.259 he's rejected the priesthood. He's bored by law. 00:11:44.399 --> 00:11:47.019 He's quit medicine and he's finally embracing 00:11:47.019 --> 00:11:49.220 mathematics. He's living with his foster mom 00:11:49.220 --> 00:11:52.039 who calls him an ass. How does he make his splash? 00:11:52.179 --> 00:11:54.899 How does he get from, you know, obscurity to 00:11:54.899 --> 00:11:57.559 the Academy of Sciences? He starts by punching 00:11:57.559 --> 00:12:01.740 up way up. In 1739, he's 22 years old and he 00:12:01.740 --> 00:12:03.740 sends a communication to the Académie de Science. 00:12:04.240 --> 00:12:06.519 But he doesn't just send a polite introductory 00:12:06.519 --> 00:12:09.399 letter. He points out a series of errors in a 00:12:09.399 --> 00:12:12.120 standard, widely used mathematics textbook called 00:12:12.120 --> 00:12:14.519 Analyse de Montreux by a man named Raynaud. That 00:12:14.519 --> 00:12:16.879 is a power move. That's like a kid in college 00:12:16.879 --> 00:12:19.059 emailing a publisher to say, hey, you know the 00:12:19.059 --> 00:12:21.220 book everyone uses to learn math. It's wrong. 00:12:21.379 --> 00:12:23.879 And here's why. It's incredibly confident, maybe 00:12:23.879 --> 00:12:26.340 even bordering on arrogant. But the key is this. 00:12:26.889 --> 00:12:28.909 He was right. And in the world of mathematics, 00:12:29.169 --> 00:12:31.429 being right is the only currency that actually 00:12:31.429 --> 00:12:33.370 matters. That got him noticed. I bet it did. 00:12:33.809 --> 00:12:37.769 So the very next year, 1740, he submits a paper 00:12:37.769 --> 00:12:41.110 on fluid mechanics, specifically on the refraction 00:12:41.110 --> 00:12:44.289 of solid bodies. This work gets recognized by 00:12:44.289 --> 00:12:47.389 Claro, who was a major mathematician of the time. 00:12:47.509 --> 00:12:50.740 And this begins his big ascent. It does. It wasn't 00:12:50.740 --> 00:12:52.799 overnight. He faced a few rejections along the 00:12:52.799 --> 00:12:55.799 way. But in 1741, he was finally elected to the 00:12:55.799 --> 00:12:58.580 Académie des Sciences. Later on, he'd be elected 00:12:58.580 --> 00:13:00.720 to the Berlin Academy and become a fellow of 00:13:00.720 --> 00:13:03.120 the Royal Society in London. He was networking 00:13:03.120 --> 00:13:05.740 with the absolute best minds in Europe. OK, let's 00:13:05.740 --> 00:13:07.820 unpack the science because we said this is a 00:13:07.820 --> 00:13:09.519 deep dive and I really want to understand what 00:13:09.519 --> 00:13:12.500 he actually did. He writes a book in 1743 called 00:13:12.500 --> 00:13:15.570 the Touré de la Dynamique. The Treatise on Dynamics. 00:13:15.590 --> 00:13:17.750 This is his masterpiece, right? It is. This is 00:13:17.750 --> 00:13:19.669 the big one. And at the heart of it is what we 00:13:19.669 --> 00:13:22.149 now call d 'Alembert's Principle. Okay, I've 00:13:22.149 --> 00:13:23.750 read the Wikipedia summary of this, and I'll 00:13:23.750 --> 00:13:26.309 be honest, my eyes glazed over. For those of 00:13:26.309 --> 00:13:28.669 us who didn't spend 50 years studying calculus, 00:13:29.090 --> 00:13:32.830 can you explain d 'Alembert's Principle? Why 00:13:32.830 --> 00:13:36.519 is it such a big deal? Let's break it down. Think 00:13:36.519 --> 00:13:39.159 about Isaac Newton. Newton gave us the fundamental 00:13:39.159 --> 00:13:42.399 laws of motion, most famously five a dollar. 00:13:42.799 --> 00:13:46.899 Force equals mass times acceleration. Right. 00:13:47.019 --> 00:13:49.539 And that's great if you are calculating something 00:13:49.539 --> 00:13:52.240 simple like how a planet moves through empty 00:13:52.240 --> 00:13:54.399 space or a cannonball flying through the air. 00:13:54.460 --> 00:13:57.179 Simple motion. But the real world is rarely that 00:13:57.179 --> 00:13:59.500 simple. What if you have a system that is constrained 00:13:59.500 --> 00:14:02.019 in some way? Constrained? What do you mean? Imagine 00:14:02.019 --> 00:14:06.120 a bead sliding along a curved wire. Or a pendulum 00:14:06.120 --> 00:14:09.320 swinging on a fixed rod. Or, maybe the best example, 00:14:09.480 --> 00:14:11.899 a roller coaster car on a track. Okay, yeah, 00:14:11.980 --> 00:14:14.159 I'm visualizing a roller coaster. The car can't 00:14:14.159 --> 00:14:16.139 just go anywhere at once, it has to follow the 00:14:16.139 --> 00:14:18.820 track. The track itself is exerting a force on 00:14:18.820 --> 00:14:21.039 the car to keep it in line. Now, if you try to 00:14:21.039 --> 00:14:23.879 calculate the motion of that car using just Newton's 00:14:23.879 --> 00:14:27.480 simple Phamelotters, it gets really, really messy. 00:14:27.820 --> 00:14:29.940 Because you have to constantly calculate the 00:14:29.940 --> 00:14:32.019 force of the track pushing back against the car 00:14:32.019 --> 00:14:35.139 at... every single millisecond, and that force 00:14:35.139 --> 00:14:37.779 is always changing direction as the track curves 00:14:37.779 --> 00:14:39.700 and dips. That sounds like a mathematical nightmare. 00:14:39.919 --> 00:14:42.240 It was. It was a massive headache for physicists 00:14:42.240 --> 00:14:44.659 and engineers. And this is where d 'Alembert 00:14:44.659 --> 00:14:47.279 found a brilliant way around it. He realized 00:14:47.279 --> 00:14:49.759 that you can just rewrite the equation. How? 00:14:49.840 --> 00:14:52.460 Instead of FOMO, you can write $5 monics. Okay, 00:14:52.620 --> 00:14:54.279 that looks like simple algebra. You just move 00:14:54.279 --> 00:14:56.220 the mod to the other side of the equation. It 00:14:56.220 --> 00:14:58.980 looks simple, but the conceptual shift is absolutely 00:14:58.980 --> 00:15:02.139 profound. He introduced the idea of a new sh**. 00:15:02.059 --> 00:15:04.519 forces, he said let's treat the acceleration 00:15:04.519 --> 00:15:07.679 part, the ma, as if it were a force pushing back 00:15:07.679 --> 00:15:10.139 against the motion. So he invented a fake force 00:15:10.139 --> 00:15:12.659 to make the math work. A fictitious force, yes. 00:15:12.940 --> 00:15:15.580 But by doing this, he converted a problem of 00:15:15.580 --> 00:15:18.259 dynamics things moving and accelerating into 00:15:18.259 --> 00:15:21.139 a problem of statics things in equilibrium, balanced. 00:15:21.480 --> 00:15:25.480 Wait. So he turned a moving movie into a frozen 00:15:25.480 --> 00:15:27.879 photograph so he could measure it more easily. 00:15:28.059 --> 00:15:31.179 That is a perfect analogy, yes. He froze the 00:15:31.179 --> 00:15:33.860 frame, mathematically speaking. By treating the 00:15:33.860 --> 00:15:36.600 system as if it were in balance, the sum of the 00:15:36.600 --> 00:15:39.220 real forces plus this new inertial force equals 00:15:39.220 --> 00:15:43.080 zero, he could use the much simpler laws of statics, 00:15:43.120 --> 00:15:46.100 a principle called virtual work, to solve these 00:15:46.100 --> 00:15:48.759 incredibly complex problems. And it let him ignore 00:15:48.759 --> 00:15:51.860 the messy parts. It allowed physicists to effectively 00:15:51.860 --> 00:15:54.840 ignore the forces of constraint. like the track 00:15:54.840 --> 00:15:57.539 pushing on the roller coaster car, and just focus 00:15:57.539 --> 00:16:00.019 on the motion itself. That is fascinating. So 00:16:00.019 --> 00:16:02.759 he basically hacked Newton's laws to make them 00:16:02.759 --> 00:16:05.620 usable for complex machines and real -world systems? 00:16:05.860 --> 00:16:08.080 Exactly. And this principle is still the foundation 00:16:08.080 --> 00:16:10.879 of what we call analytical mechanics today. If 00:16:10.879 --> 00:16:13.019 you study advanced physics or mechanical engineering, 00:16:13.279 --> 00:16:15.120 you use something called the Lagrange equations, 00:16:15.399 --> 00:16:17.159 which are directly derived from D 'Alembert's 00:16:17.159 --> 00:16:19.659 work. It's fundamental. Okay, so that's the dynamics. 00:16:19.879 --> 00:16:22.240 But he didn't stop there. He also did groundbreaking 00:16:22.240 --> 00:16:24.840 work on something called the wave equation. Yes. 00:16:25.179 --> 00:16:28.659 This is another massive, massive leap. D 'Alembert 00:16:28.659 --> 00:16:31.120 was completely fascinated by vibrating strings, 00:16:31.259 --> 00:16:34.179 like a violin string or a guitar string. Which 00:16:34.179 --> 00:16:36.019 seems pretty simple, right? You pluck it, it 00:16:36.019 --> 00:16:38.980 vibrates, wiggles back and forth. It seems simple 00:16:38.980 --> 00:16:41.500 to our eyes, but mathematically, it's an absolute 00:16:41.500 --> 00:16:45.049 beast. Think about it. A vibrating string is 00:16:45.049 --> 00:16:47.809 changing in two ways at once. It changes in time 00:16:47.809 --> 00:16:50.289 as it moves up and down, and it changes in space 00:16:50.289 --> 00:16:52.330 because the curve of the string is different 00:16:52.330 --> 00:16:54.269 at different points along its length. So you 00:16:54.269 --> 00:16:56.009 have two variables changing at the same time. 00:16:56.169 --> 00:16:58.549 Time, which we can call the dollar, and position 00:16:58.549 --> 00:17:01.350 along the string, zix large. Exactly. And before 00:17:01.350 --> 00:17:03.909 d 'Alembert, could they handle that? Not really. 00:17:04.049 --> 00:17:06.650 Calculus was still young. They could handle functions 00:17:06.650 --> 00:17:09.630 with one variable changing. d 'Alembert had to 00:17:09.630 --> 00:17:12.940 essentially invent a new kind of math. to handle 00:17:12.940 --> 00:17:15.259 both simultaneously. And that was... He developed 00:17:15.259 --> 00:17:17.339 what we now call partial differential equations. 00:17:17.539 --> 00:17:19.720 He was one of the very first to do it. And he 00:17:19.720 --> 00:17:22.279 derived the formula, the equation that describes 00:17:22.279 --> 00:17:25.400 how a wave propagates along that string. This 00:17:25.400 --> 00:17:26.980 is the crazy looking thing with the curly leads. 00:17:27.220 --> 00:17:29.019 Yeah. If I partial c do it, if I partial z do 00:17:29.019 --> 00:17:31.240 it thing. That's the one. And what's so incredible 00:17:31.240 --> 00:17:34.299 is that that equation doesn't just describe violin 00:17:34.299 --> 00:17:37.140 strings. It describes sound waves moving through 00:17:37.140 --> 00:17:39.559 the air, light waves, electromagnetic waves. 00:17:39.859 --> 00:17:42.279 The mathematical object... in that equation, 00:17:42.480 --> 00:17:45.380 the D 'Alembert operator, is absolutely critical 00:17:45.380 --> 00:17:48.900 in modern theoretical physics, from acoustics 00:17:48.900 --> 00:17:52.140 to quantum mechanics to special relativity. So 00:17:52.140 --> 00:17:54.220 he basically gave us the language to talk about 00:17:54.220 --> 00:17:56.420 how energy moves through space. In a very real 00:17:56.420 --> 00:17:59.140 sense, yes. He wrote the grammar for waves. That 00:17:59.140 --> 00:18:01.200 is just mind -blowing. So every time I hear a 00:18:01.200 --> 00:18:03.500 sound or turn on a light, the fundamental physics 00:18:03.500 --> 00:18:06.339 describing it goes back to this guy. Precisely. 00:18:06.400 --> 00:18:09.359 But... And there's almost always a but with D 00:18:09.359 --> 00:18:11.259 'Alembert. Sometimes his math was too perfect 00:18:11.259 --> 00:18:12.920 for the real world. Are we talking about the 00:18:12.920 --> 00:18:15.940 paradox now? We are. D 'Alembert's paradox. This 00:18:15.940 --> 00:18:19.359 came about around 1752. I love a good paradox. 00:18:19.519 --> 00:18:22.680 Lay it on me. Okay. So D 'Alembert was applying 00:18:22.680 --> 00:18:26.900 his fancy new calculus to the flow of fluids. 00:18:27.789 --> 00:18:30.670 liquids and gases he wanted to calculate the 00:18:30.670 --> 00:18:33.650 drag force on an object moving through a fluid 00:18:33.650 --> 00:18:35.990 like the wind resistance on a baseball or the 00:18:35.990 --> 00:18:38.609 submarine moving through water exactly now to 00:18:38.609 --> 00:18:40.869 make the math solvable with the tools he had 00:18:40.869 --> 00:18:43.470 he had to make some simplifying assumptions he 00:18:43.470 --> 00:18:46.190 assumed the fluid was ideal what does it mean 00:18:46.190 --> 00:18:49.279 an ideal fluid It means it was inviscid. So it 00:18:49.279 --> 00:18:52.519 had zero viscosity, no stickiness or internal 00:18:52.519 --> 00:18:55.380 friction, and it was incompressible, meaning 00:18:55.380 --> 00:18:58.319 its density never changes. So a perfect frictionless 00:18:58.319 --> 00:19:00.400 fluid that doesn't really exist. Right. And when 00:19:00.400 --> 00:19:03.660 he ran his equations for this ideal fluid equations, 00:19:03.759 --> 00:19:06.220 which were, I should stress, mathematically flawless, 00:19:06.420 --> 00:19:09.759 he proved that the total drag force on the object 00:19:09.759 --> 00:19:12.299 would be zero. Zero. Zero. But, I mean, if I 00:19:12.299 --> 00:19:14.220 stick my hand out of a moving car window, I feel 00:19:14.220 --> 00:19:15.720 a lot of force. If I try to run through a swimming 00:19:15.720 --> 00:19:17.859 pool, there's... definitely drag it's very much 00:19:17.859 --> 00:19:21.400 not zero exactly that's the paradox his perfect 00:19:21.400 --> 00:19:23.400 theory said there should be no resistance but 00:19:23.400 --> 00:19:25.559 reality said there is a huge amount of resistance 00:19:25.559 --> 00:19:28.920 he was stumped he famously scratched his head 00:19:28.920 --> 00:19:30.519 and said he would have to leave the explanation 00:19:30.519 --> 00:19:35.799 to future geometricians so was he stupid or was 00:19:35.799 --> 00:19:38.380 his math just broken neither his math was correct 00:19:38.380 --> 00:19:40.819 for the conditions he set the problem was that 00:19:40.819 --> 00:19:43.319 a fluid with zero viscosity doesn't exist in 00:19:43.319 --> 00:19:46.119 the real world He had idealized the problem so 00:19:46.119 --> 00:19:48.579 much that he had idealized the answer right out 00:19:48.579 --> 00:19:50.720 of existence. So what was he missing? He was 00:19:50.720 --> 00:19:53.019 missing the effects of viscosity, especially 00:19:53.019 --> 00:19:55.759 in a thin layer right next to the object surface, 00:19:55.920 --> 00:19:57.559 what we call the boundary layer. That's where 00:19:57.559 --> 00:19:59.900 all the friction happens. It took scientists 00:19:59.900 --> 00:20:03.160 decades, really, until Ludwig Prandtl in the 00:20:03.160 --> 00:20:05.839 early 20th century to fully figure out how to 00:20:05.839 --> 00:20:07.839 mathematically account for that boundary layer 00:20:07.839 --> 00:20:09.940 and resolve the paradox. It's so interesting 00:20:09.940 --> 00:20:12.930 that he kept hitting this wall. where his beautiful 00:20:12.930 --> 00:20:16.009 clean theory was just too clean for the messy 00:20:16.009 --> 00:20:18.609 real world. That is a recurring theme with D 00:20:18.609 --> 00:20:20.190 'Alembert. You're right. He loved the purity 00:20:20.190 --> 00:20:23.170 of the logic. He was a Platonist in a way. He 00:20:23.170 --> 00:20:26.359 loved the ideal form. But the world is dirty 00:20:26.359 --> 00:20:30.099 and sticky and complicated. Speaking of dirty 00:20:30.099 --> 00:20:32.339 and sticky, let's talk about politics. Let's 00:20:32.339 --> 00:20:34.220 talk about the project that really defined the 00:20:34.220 --> 00:20:37.440 entire era, the encyclopedia. The great project. 00:20:37.519 --> 00:20:39.099 I mean, you cannot talk about the Enlightenment 00:20:39.099 --> 00:20:41.160 without talking about the encyclopedia. For a 00:20:41.160 --> 00:20:44.180 modern listener, the word encyclopedia just sounds 00:20:44.180 --> 00:20:47.809 so boring. It sounds like that stack of dusty 00:20:47.809 --> 00:20:49.730 books in the school library that nobody touches 00:20:49.730 --> 00:20:52.109 anymore. But this wasn't just a reference book, 00:20:52.210 --> 00:20:54.369 was it? Oh, no, not at all. It was a war machine. 00:20:54.450 --> 00:20:57.710 It was a weapon disguised as a book. The encyclopedia, 00:20:57.970 --> 00:21:00.950 edited by Denis Diderot and d 'Alembert, was 00:21:00.950 --> 00:21:03.210 a revolutionary attempt to collect all human 00:21:03.210 --> 00:21:06.309 knowledge, science, arts, crafts, history, and 00:21:06.309 --> 00:21:08.349 present it all through the lens of reason. And 00:21:08.349 --> 00:21:10.430 why was that so dangerous? Because up until that 00:21:10.430 --> 00:21:12.750 point, knowledge was controlled by two entities, 00:21:12.970 --> 00:21:16.750 the church and the monarchy. The church decided 00:21:16.750 --> 00:21:19.490 what was true about the universe and God. The 00:21:19.490 --> 00:21:22.049 king decided what was true about society and 00:21:22.049 --> 00:21:24.789 politics. The encyclopedia came along and said, 00:21:24.930 --> 00:21:26.990 no, we can figure this stuff out for ourselves 00:21:26.990 --> 00:21:29.950 using logic, evidence and observation. It was 00:21:29.950 --> 00:21:32.450 democratizing knowledge. Exactly. It was inherently 00:21:32.450 --> 00:21:34.630 subversive. It was a direct challenge to the 00:21:34.630 --> 00:21:37.269 authority of the throne and the altar. And D 00:21:37.269 --> 00:21:39.049 'Alembert wasn't just some random contributor. 00:21:39.369 --> 00:21:41.869 He was the co -pilot of this whole thing. He 00:21:41.869 --> 00:21:44.549 was Diderot's right hand man. Diderot was the 00:21:44.549 --> 00:21:47.750 visionary. He handled the arts, literature and 00:21:47.750 --> 00:21:50.430 the philosophy. big picture. Dale and Bear was 00:21:50.430 --> 00:21:52.829 the science guy. He was in charge of all the 00:21:52.829 --> 00:21:54.829 articles on mathematics and physics. And that 00:21:54.829 --> 00:21:57.250 is a huge responsibility. It was absolutely monumental. 00:21:57.410 --> 00:21:59.589 He personally wrote over a thousand articles 00:21:59.589 --> 00:22:02.049 for it. A thousand. Can you imagine the workload? 00:22:02.549 --> 00:22:05.329 But his most famous and probably most important 00:22:05.329 --> 00:22:08.490 contribution was the preliminary discourse. This 00:22:08.490 --> 00:22:11.069 is the big introduction to the entire 35 volume 00:22:11.069 --> 00:22:13.329 set. It's so much more than an introduction. 00:22:13.789 --> 00:22:17.309 It's a manifesto for the Enlightenment. In it, 00:22:17.309 --> 00:22:19.930 he mapped out this tree of knowledge showing 00:22:19.930 --> 00:22:22.609 how all human knowledge is interconnected, growing 00:22:22.609 --> 00:22:25.450 from the trunk of reason. It celebrated the progress 00:22:25.450 --> 00:22:28.349 of the human mind. It was a declaration of intellectual 00:22:28.349 --> 00:22:31.089 independence. But doing this kind of project 00:22:31.089 --> 00:22:34.589 came with some very real risks. Diderot actually 00:22:34.589 --> 00:22:36.670 went to prison for his writing, didn't he? He 00:22:36.670 --> 00:22:39.109 did. He spent time locked up in the dungeons 00:22:39.109 --> 00:22:42.049 of Vincennes. D 'Alembert managed to stay out 00:22:42.049 --> 00:22:44.349 of jail, mostly because he was a bit more cautious, 00:22:44.430 --> 00:22:46.869 a bit less confrontational than Diderot. But 00:22:46.869 --> 00:22:49.609 the pressure was immense. The state censors were 00:22:49.609 --> 00:22:52.250 constantly breathing down their necks. The Jesuits 00:22:52.250 --> 00:22:54.690 were attacking them in pamphlets. And amidst 00:22:54.690 --> 00:22:56.869 all this pressure, D 'Alembert undergoes a kind 00:22:56.869 --> 00:22:59.630 of philosophical shift. He started out as a fairly 00:22:59.630 --> 00:23:01.609 straightforward materialist, you know, believing 00:23:01.609 --> 00:23:04.369 in just matter and motion. But he changed his 00:23:04.369 --> 00:23:06.769 views. He did. I think working on these deep 00:23:06.769 --> 00:23:09.190 philosophical questions forced him to question 00:23:09.190 --> 00:23:12.069 the nature of reality itself. He moved from that 00:23:12.069 --> 00:23:14.190 simple materialism toward a much more nuanced 00:23:14.190 --> 00:23:16.710 position of skepticism and idealism. What does 00:23:16.710 --> 00:23:19.230 that mean exactly? He famously wrote that he 00:23:19.230 --> 00:23:22.849 doubted whether there exists outside us. anything 00:23:22.849 --> 00:23:25.650 corresponding to what we suppose we see. Wait, 00:23:25.730 --> 00:23:28.470 that's very, that's very Matrix. He's questioning 00:23:28.470 --> 00:23:31.170 if the physical world is actually real. He is. 00:23:31.210 --> 00:23:33.630 He's aligning himself with philosophers like 00:23:33.630 --> 00:23:36.089 George Berkeley, and in many ways he's anticipating 00:23:36.089 --> 00:23:39.230 Immanuel Kant. He's basically saying, look, all 00:23:39.230 --> 00:23:41.069 we have is our perception of the world through 00:23:41.069 --> 00:23:44.309 our senses, but we can't be 100 % certain that 00:23:44.309 --> 00:23:46.690 the world is exactly as we perceive it. It's 00:23:46.690 --> 00:23:49.849 a very sophisticated and I think humble position 00:23:49.849 --> 00:23:52.880 for a top scientist to take. He's admitting the 00:23:52.880 --> 00:23:55.099 limits of human perception. But his humility 00:23:55.099 --> 00:23:57.140 didn't save him from controversy. We have to 00:23:57.140 --> 00:23:59.279 talk about the Geneva incident. This seems to 00:23:59.279 --> 00:24:01.460 be the moment where he really, really stumbled. 00:24:01.660 --> 00:24:04.819 The Geneva controversy of 1757. Yes, this was 00:24:04.819 --> 00:24:06.619 the beginning of the end for his involvement 00:24:06.619 --> 00:24:09.119 with the encyclopedia. So what happened? So d 00:24:09.119 --> 00:24:11.240 'Alembert writes an article for the seventh volume 00:24:11.240 --> 00:24:14.039 about the city of Geneva. Now, Geneva at the 00:24:14.039 --> 00:24:16.559 time was the international center of Calvinism, 00:24:16.579 --> 00:24:19.700 very strict, rigorous Protestantism. The city 00:24:19.700 --> 00:24:22.579 of Calvin. And in his article, D 'Alembert decides 00:24:22.579 --> 00:24:24.980 he's going to compliment the clergymen of Geneva. 00:24:25.279 --> 00:24:27.440 That sounds nice enough. Yeah. Hey, you guys 00:24:27.440 --> 00:24:29.700 in Geneva are doing a great job. Well, it depends 00:24:29.700 --> 00:24:31.960 on how you compliment them. He praised them for 00:24:31.960 --> 00:24:35.059 being so enlightened and rational that they had 00:24:35.059 --> 00:24:38.079 moved away from strict dogmatic Calvinism and 00:24:38.079 --> 00:24:41.299 toward pure Socinianism. I have no idea what 00:24:41.299 --> 00:24:43.460 Socinianism is, but I'm guessing the clergymen 00:24:43.460 --> 00:24:45.839 did not take that as a compliment. Socinianism 00:24:45.839 --> 00:24:49.059 is a specific Christian heresy. It denies the 00:24:49.059 --> 00:24:51.710 doctrine. of the Trinity. It denies the divinity 00:24:51.710 --> 00:24:54.369 of Christ. It basically says that Jesus was a 00:24:54.369 --> 00:24:57.640 great moral teacher, but he wasn't God. Oh, oh 00:24:57.640 --> 00:25:00.380 no. Exactly. D 'Alembert was essentially announcing 00:25:00.380 --> 00:25:03.160 to the entire world, hey, these pastors in Geneva 00:25:03.160 --> 00:25:05.200 are so smart, they don't even really believe 00:25:05.200 --> 00:25:07.660 in Christianity anymore. They're basically deists, 00:25:07.660 --> 00:25:10.359 like us enlightened philosophers. That is, wow. 00:25:10.559 --> 00:25:12.519 He outed them as heretics in the most famous 00:25:12.519 --> 00:25:14.960 and controversial book in Europe. It was an absolute 00:25:14.960 --> 00:25:17.640 disaster. The pastors of Geneva were furious. 00:25:17.740 --> 00:25:20.000 They were being accused of abandoning their faith 00:25:20.000 --> 00:25:22.460 in public. It caused an international diplomatic 00:25:22.460 --> 00:25:24.980 incident. Where did D 'Alembert even get this 00:25:24.980 --> 00:25:27.660 idea? Did he just make it up? No, and that's 00:25:27.660 --> 00:25:30.160 the real kicker. He got the information from 00:25:30.160 --> 00:25:33.680 Voltaire. Voltaire. The satirist. The one and 00:25:33.680 --> 00:25:36.299 only. Voltaire lived near Geneva at the time, 00:25:36.299 --> 00:25:39.619 and he loved to stir the pot. He almost certainly 00:25:39.619 --> 00:25:43.119 fed D 'Alembert this juicy insight. Oh yes, my 00:25:43.119 --> 00:25:45.140 dear D 'Alembert, the pastors here are practically 00:25:45.140 --> 00:25:47.940 atheists. You must put that in your book. Knowing 00:25:47.940 --> 00:25:50.400 full well it would cause a massive firestorm. 00:25:50.579 --> 00:25:52.599 But D 'Alembert got trolled by Voltaire. In a 00:25:52.599 --> 00:25:55.400 huge way. The backlash was severe. Jean -Jacques 00:25:55.400 --> 00:25:57.599 Rousseau, who is from Geneva and very proud of 00:25:57.599 --> 00:26:00.259 it, publicly attacked D 'Alembert for slandering 00:26:00.259 --> 00:26:02.460 his hometown. There were committees appointed 00:26:02.460 --> 00:26:05.339 to answer the charges. D 'Alembert tried to backtrack. 00:26:05.359 --> 00:26:07.480 He tried to excuse himself by saying he just 00:26:07.480 --> 00:26:08.880 meant they didn't accept the authority of the 00:26:08.880 --> 00:26:11.519 pope in Rome, but the damage was done. And the 00:26:11.519 --> 00:26:13.759 stress just got to him. It did. He was tired 00:26:13.759 --> 00:26:15.519 of the constant fighting. He was tired of the 00:26:15.519 --> 00:26:18.099 threats of censorship. He was, I think, fundamentally 00:26:18.099 --> 00:26:21.140 a more timid person than Diderot. He resigned 00:26:21.140 --> 00:26:23.339 from his editorship of the Encyclopedia. He just 00:26:23.339 --> 00:26:26.140 walked away. And left Diderot to finish the whole 00:26:26.140 --> 00:26:28.559 project alone. Pretty much. He went back to a 00:26:28.559 --> 00:26:30.920 safe place. He went back to his math. But he 00:26:30.920 --> 00:26:33.299 didn't stop trying to apply that math to other 00:26:33.299 --> 00:26:36.420 fields. Which brings us to a field where he really 00:26:36.420 --> 00:26:39.920 ruffled some feathers. Music. Oh, yes. I love 00:26:39.920 --> 00:26:42.220 this part of his story. Because we think of music 00:26:42.220 --> 00:26:47.059 as art, as emotion, as soul. But de Lambert looked 00:26:47.059 --> 00:26:50.529 at a violin and saw a calculus problem. He really 00:26:50.529 --> 00:26:53.329 did. He was absolutely convinced that since sound 00:26:53.329 --> 00:26:56.210 is just vibration and vibration is physics and 00:26:56.210 --> 00:26:59.009 physics is described by math, then music must 00:26:59.009 --> 00:27:01.369 be a branch of mathematics. It was that simple 00:27:01.369 --> 00:27:03.349 to him. But at first he found a partner in this 00:27:03.349 --> 00:27:05.970 line of thinking, the composer Jean -Philippe 00:27:05.970 --> 00:27:08.829 Rameau. Rameau is a giant. He's the back of France, 00:27:08.950 --> 00:27:10.910 basically, the most important French composer 00:27:10.910 --> 00:27:12.630 of the 18th century. And what was the connection? 00:27:13.079 --> 00:27:15.519 Well, Rameau had written his own highly influential 00:27:15.519 --> 00:27:18.039 treatise on harmony that was very theoretical. 00:27:18.359 --> 00:27:20.799 He was trying to explain why certain chords sound 00:27:20.799 --> 00:27:23.000 good together using the physics of overtones 00:27:23.000 --> 00:27:26.619 and harmonic series. d 'Alembert read it in 1749, 00:27:26.700 --> 00:27:29.619 and he loved it. He praised Rameau's deductive 00:27:29.619 --> 00:27:32.980 character. He saw a kindred spirit, someone else 00:27:32.980 --> 00:27:35.099 who was trying to systematize art and find its 00:27:35.099 --> 00:27:37.099 rational principles. If they were friends. At 00:27:37.099 --> 00:27:40.420 first, yes. In 1752, d 'Alembert even wrote his 00:27:40.420 --> 00:27:43.240 own book, Elements de Musique. which was an attempt 00:27:43.240 --> 00:27:46.460 to summarize and simplify Rameau's complex theories 00:27:46.460 --> 00:27:49.519 for the general public. He wanted to be Rameau's 00:27:49.519 --> 00:27:51.880 popularizer. That sounds helpful. Here, let me 00:27:51.880 --> 00:27:53.819 translate this genius work for the common man. 00:27:54.019 --> 00:27:56.200 It was certainly meant to be, but here's the 00:27:56.200 --> 00:27:58.940 problem. d 'Alembert wasn't a musician. He was 00:27:58.940 --> 00:28:01.500 a mathematician. So when he encountered parts 00:28:01.500 --> 00:28:04.119 of Rameau's theory that were a bit messy or complex 00:28:04.119 --> 00:28:07.319 or relied on the musician's ear rather than pure 00:28:07.319 --> 00:28:10.799 numbers, he, well, he fixed them. He fixed the 00:28:10.799 --> 00:28:13.809 music theory. Without being a musician. He changed 00:28:13.809 --> 00:28:16.730 certain concepts to make them fit his neat mathematical 00:28:16.730 --> 00:28:20.130 equations better. He argued that Rameau's core 00:28:20.130 --> 00:28:23.990 idea of the core sonore, the sounding body, wasn't 00:28:23.990 --> 00:28:26.589 sufficient to explain everything. He tried to 00:28:26.589 --> 00:28:28.869 impose a logical structure that the music itself 00:28:28.869 --> 00:28:31.670 didn't necessarily support. I can just imagine 00:28:31.670 --> 00:28:34.349 how Rameau felt about that. Thanks for explaining 00:28:34.349 --> 00:28:36.309 my life's work to everyone, but you changed all 00:28:36.309 --> 00:28:38.349 the important parts and you don't even play the 00:28:38.349 --> 00:28:41.180 harpsichord. Romo was absolutely furious. He 00:28:41.180 --> 00:28:43.819 felt d 'Alembert had completely misconstrued 00:28:43.819 --> 00:28:47.319 the finer points. Plus, Romo was already angry 00:28:47.319 --> 00:28:49.700 about the articles on music that Rousseau was 00:28:49.700 --> 00:28:52.220 writing for the Encyclopédie, which he also thought 00:28:52.220 --> 00:28:54.660 were nonsense. He felt surrounded by these philosophers 00:28:54.660 --> 00:28:57.299 who couldn't compose a simple tune, but wanted 00:28:57.299 --> 00:28:59.720 to tell him how music worked. So he turned on 00:28:59.720 --> 00:29:02.079 d 'Alembert. Viciously. They had a series of 00:29:02.079 --> 00:29:04.539 bitter public exchanges in the press. The friendship 00:29:04.539 --> 00:29:07.309 was completely over. And it really reveals D 00:29:07.309 --> 00:29:09.490 'Alembert's intellectual arrogance, doesn't it? 00:29:09.549 --> 00:29:13.130 It does. He had this very Baroque bias. He believed 00:29:13.130 --> 00:29:15.970 that the modern music of his own time was the 00:29:15.970 --> 00:29:19.109 pinnacle of perfection. He actually argued that 00:29:19.109 --> 00:29:21.710 the music of the ancients, the Greeks and Romans, 00:29:21.809 --> 00:29:25.049 was worthless. Worthless. The foundation of Western 00:29:25.049 --> 00:29:27.779 music. He claimed that because we don't have 00:29:27.779 --> 00:29:30.039 their sheet music and because time had destroyed 00:29:30.039 --> 00:29:32.279 their models, there was nothing to look back 00:29:32.279 --> 00:29:35.240 to. He just dismissed the entire history of music 00:29:35.240 --> 00:29:38.279 before his own era as irrelevant. That's an incredibly 00:29:38.279 --> 00:29:41.400 harsh take. And it gets worse. He also claimed 00:29:41.400 --> 00:29:44.000 that music couldn't imitate reality as well as 00:29:44.000 --> 00:29:46.619 painting or poetry because musicians simply lacked 00:29:46.619 --> 00:29:49.680 inventiveness. Wow. He really looked down on 00:29:49.680 --> 00:29:51.740 the artist, didn't he? He valued the structure 00:29:51.740 --> 00:29:54.400 of the music, the math of the frequencies, far 00:29:54.400 --> 00:29:56.799 more than he valued the creative act of the musician. 00:29:57.279 --> 00:30:00.140 It's a classic case of a specialist in one field 00:30:00.140 --> 00:30:02.779 math trying to force another field music to play 00:30:02.779 --> 00:30:05.099 by his own rigid rules. Speaking of forcing things 00:30:05.099 --> 00:30:08.039 to play by rules, we absolutely have to talk 00:30:08.039 --> 00:30:10.160 about the gambling. The gambler's fallacy. This 00:30:10.160 --> 00:30:12.019 is one of the most famous things associated with 00:30:12.019 --> 00:30:14.819 his name, but for all the wrong reasons. Yes. 00:30:15.180 --> 00:30:17.680 It appears in his work, Quote We Peeler. which 00:30:17.680 --> 00:30:20.819 means head or tail. So lay out the d 'Alembert 00:30:20.819 --> 00:30:23.779 system for us. What was his big wrong idea? D 00:30:23.779 --> 00:30:26.259 'Alembert argued quite seriously that if you 00:30:26.259 --> 00:30:28.980 flip a coin and it comes up tails, the probability 00:30:28.980 --> 00:30:31.500 of it landing on heads for the next flip actually 00:30:31.500 --> 00:30:33.859 increases. Okay, stop right there. I have to 00:30:33.859 --> 00:30:36.539 push back here. This is the man who invented 00:30:36.539 --> 00:30:39.880 partial differential equations. He understands 00:30:39.880 --> 00:30:42.680 calculus better than almost anyone alive at the 00:30:42.680 --> 00:30:45.539 time. How on earth does he not understand that 00:30:45.539 --> 00:30:47.980 a corn doesn't have a memory? Is he just being 00:30:47.980 --> 00:30:50.539 stupid or are we missing something? It's not 00:30:50.539 --> 00:30:53.359 stupidity. It's a philosophical blind spot. He 00:30:53.359 --> 00:30:55.519 believed in what he called a maturity of chances. 00:30:56.140 --> 00:30:58.500 He had this deep -seated feeling that nature, 00:30:58.680 --> 00:31:01.259 or the universe, prefers balance. If there's 00:31:01.259 --> 00:31:03.480 an excess of tails, he thought nature must provide 00:31:03.480 --> 00:31:06.119 a head soon to balance the cosmic scales. But 00:31:06.119 --> 00:31:08.920 that feels so intuitive. If I'm at a roulette 00:31:08.920 --> 00:31:11.099 wheel and it lands on red ten times in a row, 00:31:11.279 --> 00:31:13.900 every single bone in my body screams black as 00:31:13.900 --> 00:31:16.619 dew. And that is exactly why casinos are rich 00:31:16.619 --> 00:31:18.799 and gamblers are not. Because the roulette ball 00:31:18.799 --> 00:31:21.039 doesn't know where it landed on the last spin. 00:31:21.630 --> 00:31:24.470 The odds are 50 -50 or slightly less because 00:31:24.470 --> 00:31:26.769 of the green zero every single time. They are 00:31:26.769 --> 00:31:29.670 independent events. But d 'Alembert, the great 00:31:29.670 --> 00:31:32.509 mathematician, he defended this fallacy. He did. 00:31:32.630 --> 00:31:35.049 He argued passionately against the conventional 00:31:35.049 --> 00:31:37.210 probability theory that had been developed by 00:31:37.210 --> 00:31:40.470 Pascal and Fermat. And this mistaken belief led 00:31:40.470 --> 00:31:42.769 directly to the betting system that still bears 00:31:42.769 --> 00:31:46.230 his name, the Martingale system or d 'Alembert 00:31:46.230 --> 00:31:48.650 system. How did the system work? The idea is 00:31:48.650 --> 00:31:50.829 simple. Every time you lose a bet, you increase 00:31:50.829 --> 00:31:52.910 your next spread, usually by doubling it. Why? 00:31:53.230 --> 00:31:56.009 Because you believe you are due for a win. And 00:31:56.009 --> 00:31:58.549 when that inevitable win finally comes, it will 00:31:58.549 --> 00:32:00.450 be large enough to cover all your previous losses 00:32:00.450 --> 00:32:03.750 plus a small profit. Then, if you win, you go 00:32:03.750 --> 00:32:06.230 back to your original smaller bet. I mean, on 00:32:06.230 --> 00:32:08.089 paper, if you have to win eventually, you'll 00:32:08.089 --> 00:32:10.920 make your money back. On paper, with an infinite 00:32:10.920 --> 00:32:13.519 amount of money and no table limits, yes, it 00:32:13.519 --> 00:32:16.299 works. But in the real world, two things happen. 00:32:16.559 --> 00:32:19.359 One, you hit a losing streak that is so long 00:32:19.359 --> 00:32:21.319 you simply run out of money to double your bet 00:32:21.319 --> 00:32:23.819 again. Or two. Or two, you hit the table limit. 00:32:24.000 --> 00:32:26.900 The casino literally has a rule that says you 00:32:26.900 --> 00:32:29.160 cannot bet more than a certain amount precisely 00:32:29.160 --> 00:32:31.720 to stop systems like this. And then you lose 00:32:31.720 --> 00:32:33.940 everything. You lose everything. Exponential 00:32:33.940 --> 00:32:36.180 growth is a scary thing when it's working against 00:32:36.180 --> 00:32:39.460 you. If you start with a $10 bet and you lose 00:32:39.460 --> 00:32:42.339 just 10 times in a row, your 11th bet has to 00:32:42.339 --> 00:32:46.339 be over $10 ,000. Ouch. The fact that d 'Alembert, 00:32:46.559 --> 00:32:50.359 the man of pure reason, the man who scorned imprecision, 00:32:50.359 --> 00:32:53.119 defended this system just shows that even in 00:32:53.119 --> 00:32:55.940 the age of reason, human intuition is a powerful 00:32:55.940 --> 00:32:58.720 and often misleading drug. He wanted the universe 00:32:58.720 --> 00:33:00.720 to be fair and balanced, even when it's just 00:33:00.720 --> 00:33:03.920 random. I find it so incredibly humanizing. He's 00:33:03.920 --> 00:33:07.319 calculating the drag of fluids in an ideal frictionless 00:33:07.319 --> 00:33:10.099 space, but he can't figure out a simple coin 00:33:10.099 --> 00:33:12.980 toss. It makes him feel like a real person, not 00:33:12.980 --> 00:33:15.680 just a historical figure. It does. And that brings 00:33:15.680 --> 00:33:18.079 us to his personal life. He wasn't just a brain 00:33:18.079 --> 00:33:20.799 in a jar. He was a socialite. He was a regular 00:33:20.799 --> 00:33:23.859 in the Parisian salons. the great salons of Marie 00:33:23.859 --> 00:33:25.960 -Thérèse Rodegefant and the Marquise du Deform. 00:33:26.380 --> 00:33:29.680 These were the intellectual and social hubs of 00:33:29.680 --> 00:33:32.539 Paris. You have to picture a living room filled 00:33:32.539 --> 00:33:35.039 with the smartest, most influential people in 00:33:35.039 --> 00:33:39.200 Europe. Writers, scientists, diplomats, aristocrats, 00:33:39.240 --> 00:33:42.000 all drinking coffee, arguing about God and the 00:33:42.000 --> 00:33:45.039 king, and of course, gossiping. And this is where 00:33:45.039 --> 00:33:47.579 he met Julie de Lisbonasse. His great love story. 00:33:47.900 --> 00:33:51.599 Julie was the paid companion, or reader, to the 00:33:51.599 --> 00:33:54.259 Marquise du Défense. She was brilliant, she was 00:33:54.259 --> 00:33:56.779 charming, she was witty, and d 'Alembert was 00:33:56.779 --> 00:33:59.319 completely smitten. And it wasn't just a passing 00:33:59.319 --> 00:34:01.819 crush, was it? It became a very serious partnership. 00:34:02.259 --> 00:34:05.200 It did. When Julie had a major falling out with 00:34:05.200 --> 00:34:06.500 the Marquise, marquees and was essentially kicked 00:34:06.500 --> 00:34:08.519 out onto the street, D 'Alembert did something 00:34:08.519 --> 00:34:10.639 very scandalous for the time. He moved in with 00:34:10.639 --> 00:34:13.420 her. In the 18th century, an unmarried man and 00:34:13.420 --> 00:34:15.219 woman living together. That's incredibly bold. 00:34:15.440 --> 00:34:17.860 It was, but he didn't seem to care about the 00:34:17.860 --> 00:34:20.380 gossip. He nursed her through a terrible bout 00:34:20.380 --> 00:34:23.039 of smallpox. He was completely devoted to her. 00:34:23.159 --> 00:34:26.079 They lived together until her death in 1776. 00:34:26.440 --> 00:34:29.179 Did they ever marry? No, they never did. But 00:34:29.179 --> 00:34:32.039 the bond was undeniable. Her death absolutely 00:34:32.039 --> 00:34:35.210 devastated him. He spent the last years of his 00:34:35.210 --> 00:34:37.769 life in a deep gloom, living in a small apartment 00:34:37.769 --> 00:34:40.630 at the Louvre. At the Louvre. The museum. Yes, 00:34:40.630 --> 00:34:43.269 because as the perpetual secretary of the Académie 00:34:43.269 --> 00:34:45.809 Française, he was given official rooms there. 00:34:45.969 --> 00:34:48.750 And Diderot, his old partner, even wrote a fictional 00:34:48.750 --> 00:34:51.090 version of him, right? Le Rêve de D 'Alembert 00:34:51.090 --> 00:34:54.030 or Alambert's Dream. Yes, although that was written 00:34:54.030 --> 00:34:56.250 after Diderot and d 'Alembert had drifted apart. 00:34:56.570 --> 00:34:59.469 Yeah. In the story, d 'Alembert is sick in bed, 00:34:59.670 --> 00:35:02.780 muttering philosophy in his sleep. Diderot uses 00:35:02.780 --> 00:35:05.139 the character of d 'Alembert to explore these 00:35:05.139 --> 00:35:08.739 really radical materialist ideas, ideas that 00:35:08.739 --> 00:35:10.960 the real d 'Alembert had arguably moved away 00:35:10.960 --> 00:35:13.239 from by that point. And a fascinating literary 00:35:13.239 --> 00:35:15.960 caricature. It is, and it shows how iconic he 00:35:15.960 --> 00:35:17.760 had become. He was a character in other people's 00:35:17.760 --> 00:35:19.980 fiction now. So we have the math, the music, 00:35:20.159 --> 00:35:23.019 the love, the controversy. How does it all end 00:35:23.019 --> 00:35:26.500 for him? He died in October of 1783 at the age 00:35:26.500 --> 00:35:29.710 of 65. He had suffered from a urinary bladder 00:35:29.710 --> 00:35:32.429 illness for years, most likely bladder stones. 00:35:33.150 --> 00:35:35.789 It was, by all accounts, a very painful end. 00:35:36.010 --> 00:35:38.369 And what about the burial? Was he honored as 00:35:38.369 --> 00:35:40.570 a great mind of France? This is the final insult, 00:35:40.610 --> 00:35:42.489 and it really brings us full circle back to his 00:35:42.489 --> 00:35:45.530 birth. Because he was a known unbeliever, an 00:35:45.530 --> 00:35:47.809 agnostic or a deist who had angered the church 00:35:47.809 --> 00:35:50.829 his whole life with his writings, he was refused 00:35:50.829 --> 00:35:53.849 a Christian burial. Just like Voltaire had been 00:35:53.849 --> 00:35:56.480 a few years earlier. Exactly. The church did 00:35:56.480 --> 00:35:59.539 not forgive. He was buried in a common, unmarked 00:35:59.539 --> 00:36:02.099 grave in the Saint -Jean -Laurent district, ironically, 00:36:02.300 --> 00:36:04.440 right near the church where he was first found 00:36:04.440 --> 00:36:07.000 as a baby. The man who helped to find the Enlightenment, 00:36:07.119 --> 00:36:09.440 buried in a pit with no name. Just like he was 00:36:09.440 --> 00:36:11.900 found on the steps with no name. That is, it's 00:36:11.900 --> 00:36:14.320 poetic and it's terrible at the same time. But 00:36:14.320 --> 00:36:17.219 his legacy couldn't be buried. You can refuse 00:36:17.219 --> 00:36:19.940 him a tombstone, but you can't erase the mathematics. 00:36:20.730 --> 00:36:23.489 We still have the Delamere -Gauss theorem, which 00:36:23.489 --> 00:36:25.489 you may know as the fundamental theorem of algebra. 00:36:25.789 --> 00:36:28.630 We have the ratio test for determining if an 00:36:28.630 --> 00:36:31.550 infinite series converges. We have the d 'Alembert 00:36:31.550 --> 00:36:34.090 operator in physics. And there's even an island 00:36:34.090 --> 00:36:37.250 named after him, isn't there? There is. Île d 00:36:37.250 --> 00:36:40.230 'Alembert in South Australia, named by the French 00:36:40.230 --> 00:36:43.250 explorer Nicolas Baudin. And what about the moon 00:36:43.250 --> 00:36:47.809 of Venus? Or, almost. Ah, yes. The final great 00:36:47.809 --> 00:36:50.280 anecdote. Frederick the Great of Prussia, who 00:36:50.280 --> 00:36:52.460 was a huge admirer of d 'Alembert, he tried to 00:36:52.460 --> 00:36:54.320 hire him to run the Berlin Academy many times, 00:36:54.500 --> 00:36:57.840 proposed naming a suspected moon a Venus d 'Alembert. 00:36:57.960 --> 00:37:00.619 A moon of Venus. But Venus doesn't have a moon. 00:37:00.760 --> 00:37:02.980 We know that now. But back in the 18th century, 00:37:03.179 --> 00:37:04.760 some astronomers thought they saw one. It was 00:37:04.760 --> 00:37:07.139 a recurring observation, probably an optical 00:37:07.139 --> 00:37:09.900 illusion or a distant star. And d 'Alembert was 00:37:09.900 --> 00:37:11.440 offered the honor of having it named for him. 00:37:11.539 --> 00:37:14.500 He was, and he turned it down. Maybe it was modesty. 00:37:14.619 --> 00:37:16.579 Perhaps he knew the sighting was dubious. He 00:37:16.579 --> 00:37:19.559 was a skeptic to his core, remember? Or maybe 00:37:19.559 --> 00:37:21.659 he just didn't need his name in the sky to know 00:37:21.659 --> 00:37:24.239 that he mattered. And it's a good thing he refused, 00:37:24.500 --> 00:37:26.219 because the moon, of course, turned out not to 00:37:26.219 --> 00:37:29.280 exist at all. That was a smart move. You definitely 00:37:29.280 --> 00:37:31.420 don't want to be the namesake of a cosmic mistake. 00:37:31.760 --> 00:37:34.679 Indeed. So, let's wrap all this up. What does 00:37:34.679 --> 00:37:37.719 it all mean? When we look at this incredible 00:37:37.719 --> 00:37:40.780 life, the foundling on the church steps, the 00:37:40.780 --> 00:37:42.980 Glacier's foster son, the academic superstar, 00:37:43.219 --> 00:37:45.780 the encyclopedist, what's the final takeaway? 00:37:46.099 --> 00:37:48.920 For me, he was the ultimate connector. He tried 00:37:48.920 --> 00:37:51.599 to connect physics to math, math to music, and 00:37:51.599 --> 00:37:53.599 philosophy to the general public through the 00:37:53.599 --> 00:37:56.760 encyclopedia. He truly believed that the world 00:37:56.760 --> 00:37:59.500 was understandable, that it was rational. He 00:37:59.500 --> 00:38:00.960 believed that if you just thought hard enough, 00:38:00.980 --> 00:38:03.340 you could write an equation for everything, from 00:38:03.340 --> 00:38:05.599 the drag of water on a ship to the melody of 00:38:05.599 --> 00:38:08.059 a flute. Even if he sometimes had to oversimplify 00:38:08.059 --> 00:38:10.340 the world to make it fit into his neat equations. 00:38:10.619 --> 00:38:13.199 He had the courage to try. He lived in a time 00:38:13.199 --> 00:38:16.139 of chaos and superstition and authority, and 00:38:16.139 --> 00:38:18.280 he tried to build a scaffold of reason for people 00:38:18.280 --> 00:38:20.320 to climb on. I just keep coming back to that 00:38:20.320 --> 00:38:22.940 quote from his foster mother. You will never 00:38:22.940 --> 00:38:25.599 be anything but a philosopher. And what is that 00:38:25.599 --> 00:38:28.300 but an ass who plagues himself all his life? 00:38:28.440 --> 00:38:30.679 That he may be talked about after he is dead. 00:38:31.000 --> 00:38:33.480 She was wrong. He wasn't plaguing himself for 00:38:33.480 --> 00:38:35.760 nothing. He was building the foundation of the 00:38:35.760 --> 00:38:39.099 modern world. Every engineer calculating the 00:38:39.099 --> 00:38:41.699 stress on a bridge, every physicist studying 00:38:41.699 --> 00:38:44.380 wave mechanics, every single person who looks 00:38:44.380 --> 00:38:47.579 up a fact in an encyclopedia, they are all standing 00:38:47.579 --> 00:38:49.699 on his shoulders, whether they know it or not. 00:38:50.000 --> 00:38:52.059 So here's my final question for you, listening 00:38:52.059 --> 00:38:55.070 to this right now. We live in an age of incredible 00:38:55.070 --> 00:38:57.289 information overload, maybe even more so than 00:38:57.289 --> 00:38:59.429 the readers of the Encyclopedia did. And we have 00:38:59.429 --> 00:39:01.429 specialists for everything. We have people who 00:39:01.429 --> 00:39:03.889 spend their entire lives studying just one protein 00:39:03.889 --> 00:39:07.210 or one type of coding language. But do we have 00:39:07.210 --> 00:39:09.610 enough Dellen Bears? Do we have enough people 00:39:09.610 --> 00:39:13.150 who are brave enough or maybe arrogant enough 00:39:13.150 --> 00:39:16.150 to try to synthesize it all, to try to understand 00:39:16.150 --> 00:39:19.409 music and fluid dynamics and philosophy? Even 00:39:19.409 --> 00:39:20.929 if they get the coin flip wrong occasionally. 00:39:21.510 --> 00:39:24.630 Exactly. Is the risk of being spectacularly wrong 00:39:24.630 --> 00:39:27.150 in one field worth the attempt to try and understand 00:39:27.150 --> 00:39:29.590 everything? I think D 'Alembert would say yes. 00:39:29.869 --> 00:39:32.710 And looking back at his life, I have to say I 00:39:32.710 --> 00:39:35.750 think he's right. Thanks for diving deep with 00:39:35.750 --> 00:39:37.769 us today. It's been a real pleasure. We'll see 00:39:37.769 --> 00:39:38.269 you next time.