WEBVTT 00:00:00.000 --> 00:00:02.580 I think. Therefore, I am. It's the philosophical 00:00:02.580 --> 00:00:06.639 equivalent of just do it. Everyone knows it's 00:00:06.639 --> 00:00:09.240 on T -shirts. It's on coffee mugs. It's probably 00:00:09.240 --> 00:00:12.919 tattooed on a few undergrads right now. Cogito 00:00:12.919 --> 00:00:16.539 ergo sum. It is the catchphrase of Western civilization, 00:00:16.800 --> 00:00:19.620 essentially the bedrock. Right. But here's the 00:00:19.620 --> 00:00:22.699 thing. When I hear that phrase, I picture a very 00:00:22.699 --> 00:00:26.019 serious old guy in a wig, you know, sitting at 00:00:26.019 --> 00:00:29.019 a mahogany desk with a quill, having this profound 00:00:29.019 --> 00:00:32.460 moment of clarity. I do not picture a mercenary 00:00:32.460 --> 00:00:35.159 soldier shivering in the middle of a German winter, 00:00:35.259 --> 00:00:38.079 locking himself inside a heating furnace to hallucinate. 00:00:38.240 --> 00:00:40.320 It is a bit of a disconnect, isn't it? The foundation 00:00:40.320 --> 00:00:43.219 of rational thought coming from a man who was, 00:00:43.259 --> 00:00:45.460 well, arguably having a nervous breakdown in 00:00:45.460 --> 00:00:47.880 a very small, very hot room. And it gets weirder. 00:00:47.920 --> 00:00:49.259 I mean, we're talking about a guy who believed 00:00:49.259 --> 00:00:51.359 that if you kicked a dog, it didn't feel pain 00:00:51.359 --> 00:00:53.619 because it was just a broken machine making a 00:00:53.619 --> 00:00:56.460 squeaking noise. And guy whose skull, his actual 00:00:56.460 --> 00:00:59.759 physical head bone, was stolen, sold, swapped 00:00:59.759 --> 00:01:02.000 and passed around Europe like a grim trading 00:01:02.000 --> 00:01:05.260 card for centuries. It is a story that has everything. 00:01:05.459 --> 00:01:09.879 War, visions, stolen body parts and a fundamental 00:01:09.879 --> 00:01:12.780 rewiring of how humans understand reality itself. 00:01:13.120 --> 00:01:16.890 Exactly. So today we are doing a deep dive into 00:01:16.890 --> 00:01:19.150 Rene Descartes. But we're not just going to recite 00:01:19.150 --> 00:01:21.810 his Wikipedia page. We want to understand how 00:01:21.810 --> 00:01:23.950 he broke the world and how he put it back together. 00:01:24.349 --> 00:01:26.530 Because whether we realize it or not, we are 00:01:26.530 --> 00:01:28.609 all living in the house that Descartes built. 00:01:28.810 --> 00:01:31.250 We absolutely are. He's also called the father 00:01:31.250 --> 00:01:33.730 of modern philosophy, which sounds like a nice 00:01:33.730 --> 00:01:36.010 title to put on a resume, but it implies something 00:01:36.010 --> 00:01:38.769 massive. Before him, knowledge was about authority, 00:01:39.010 --> 00:01:41.510 the church, Aristotle. After him, knowledge was 00:01:41.510 --> 00:01:44.209 about you, the individual. So we have a stack 00:01:44.209 --> 00:01:46.230 of sources here, his biographies, his letters, 00:01:46.250 --> 00:01:48.269 and the big ones, discourse on the method and 00:01:48.269 --> 00:01:50.609 meditations on first philosophy. Our mission, 00:01:50.730 --> 00:01:52.890 to track this guy from the stove to the skull 00:01:52.890 --> 00:01:55.510 and figure out if he was a genius, a madman, 00:01:55.530 --> 00:01:58.030 or both. I would argue he was a bit of both, 00:01:58.109 --> 00:02:00.709 definitely. But to understand the madness, you 00:02:00.709 --> 00:02:02.609 have to understand where he started. Let's rewind 00:02:02.609 --> 00:02:06.540 to the beginning then, 1596. La Haye -en -Touraine, 00:02:06.719 --> 00:02:09.560 France. A town so proud of him, they literally 00:02:09.560 --> 00:02:12.340 renamed it Descartes. Which, by the way, is a 00:02:12.340 --> 00:02:15.199 total power move. It is. Imagine having a town 00:02:15.199 --> 00:02:18.060 named Smith or Jones. It's a significant honor. 00:02:18.719 --> 00:02:21.259 But his start in life was incredibly fragile. 00:02:21.560 --> 00:02:24.539 His mother, Jeanne, died just a few days after 00:02:24.539 --> 00:02:26.960 childbirth, about a year after René was born. 00:02:27.319 --> 00:02:30.419 So he's an infant, motherless, and incredibly 00:02:30.419 --> 00:02:33.120 sickly. The doctors didn't think he would survive 00:02:33.120 --> 00:02:34.860 childhood. He was raised by his grandmother, 00:02:35.020 --> 00:02:37.360 right? His father was always away. Yes, his father 00:02:37.360 --> 00:02:39.439 was a busy man, a counselor in the Parliament 00:02:39.439 --> 00:02:41.840 of Brittany, so he was away on business constantly. 00:02:42.340 --> 00:02:44.400 Rene was left in this quiet, rural environment, 00:02:44.520 --> 00:02:46.300 constantly being told he was too weak to play, 00:02:46.379 --> 00:02:49.460 too weak to run. And that fragility, that sense 00:02:49.460 --> 00:02:51.500 of being delicate, it really shaped his entire 00:02:51.500 --> 00:02:54.280 lifestyle. This brings us to the one detail about 00:02:54.280 --> 00:02:55.900 his school life that I am infinitely jealous 00:02:55.900 --> 00:02:58.259 of. He goes to this fancy Jesuit college, La 00:02:58.259 --> 00:03:00.819 Flèche. It's basically the Harvard of 17th century 00:03:00.819 --> 00:03:03.099 France. Strict discipline, rigorous schedule. 00:03:03.580 --> 00:03:06.819 But René, he gets a pass. The Jesuits were smart. 00:03:06.879 --> 00:03:09.379 They were very pragmatic. They saw he was brilliant, 00:03:09.539 --> 00:03:13.060 but physically delicate. So while the other students 00:03:13.060 --> 00:03:15.960 were up at 5 a .m. for prayers and chores, Descartes 00:03:15.960 --> 00:03:17.960 was allowed to stay in bed until noon. Until 00:03:17.960 --> 00:03:20.699 noon, in a boarding school. That is the dream. 00:03:21.240 --> 00:03:23.460 I mean, can you imagine? But he wasn't just sleeping. 00:03:23.520 --> 00:03:26.280 He was lying there, awake, staring at the ceiling, 00:03:26.460 --> 00:03:30.099 thinking. He did map in his head. He contemplated 00:03:30.099 --> 00:03:32.960 philosophy. He developed this lifelong habit 00:03:32.960 --> 00:03:35.599 of doing his heavy intellectual lifting while 00:03:35.599 --> 00:03:39.379 horizontal. He needed that quiet, warm solitude 00:03:39.379 --> 00:03:41.930 to function. It's funny because we think of working 00:03:41.930 --> 00:03:44.210 hard as sweating, running around, being dizzy. 00:03:44.789 --> 00:03:46.789 Descartes' version of working hard was lying 00:03:46.789 --> 00:03:49.270 under a duvet for seven hours staring at a fly 00:03:49.270 --> 00:03:51.830 on the ceiling. And that habit of solitude is 00:03:51.830 --> 00:03:53.729 crucial. Because even though he was getting the 00:03:53.729 --> 00:03:56.349 best education money could buy, learning Latin, 00:03:56.409 --> 00:03:59.069 Greek, Aristotelian physics, he started to get 00:03:59.069 --> 00:04:01.310 this nagging feeling. A feeling that would eventually, 00:04:01.469 --> 00:04:03.569 you know, tear down Western philosophy. The feeling 00:04:03.569 --> 00:04:06.050 that it was all nonsense. Not necessarily nonsense, 00:04:06.310 --> 00:04:11.030 but shaky. Unreliable. He looked at what he was 00:04:11.030 --> 00:04:14.330 being taught, the physics of Aristotle, which 00:04:14.330 --> 00:04:16.629 said rocks fall because they want to go home 00:04:16.629 --> 00:04:18.689 to the center of the earth. Right. Purpose driven 00:04:18.689 --> 00:04:22.050 physics. Exactly. Or the scholastic philosophy 00:04:22.050 --> 00:04:25.149 that relied entirely on, well, the church says 00:04:25.149 --> 00:04:28.610 this or Aristotle wrote that. He realized that 00:04:28.610 --> 00:04:31.089 none of it was proven. It was all just people 00:04:31.089 --> 00:04:33.389 repeating what other people had said for centuries. 00:04:33.750 --> 00:04:35.329 It's like playing a game of telephone that's 00:04:35.329 --> 00:04:37.589 been going on for 2000 years. At some point you 00:04:37.589 --> 00:04:39.709 realize, wait. How do I know the guy at the front 00:04:39.709 --> 00:04:42.069 of the line actually saw anything? That is the 00:04:42.069 --> 00:04:44.730 perfect analogy. He left school feeling that 00:04:44.730 --> 00:04:46.790 the only thing he had really learned was how 00:04:46.790 --> 00:04:49.389 ignorant he was. He had a law degree, he had 00:04:49.389 --> 00:04:52.029 a classical education, and he felt he knew absolutely 00:04:52.029 --> 00:04:55.009 nothing for certain. So naturally, the fragile 00:04:55.009 --> 00:04:57.430 guy who loves sleeping in and doubts everything 00:04:57.430 --> 00:05:00.870 decides to become a mercenary soldier. Makes 00:05:00.870 --> 00:05:02.430 that make sense. It does seem like a hard left 00:05:02.430 --> 00:05:05.790 turn, doesn't it? I am frail and I love philosophy. 00:05:06.029 --> 00:05:08.410 Please hand me a pike and send me to the 30 years 00:05:08.410 --> 00:05:11.069 war. It's completely counterintuitive. But you 00:05:11.069 --> 00:05:13.329 have to understand the era. If you wanted to 00:05:13.329 --> 00:05:16.050 see the world, really see it, you joined an army. 00:05:16.589 --> 00:05:19.009 And more importantly, Descartes was interested 00:05:19.009 --> 00:05:22.250 in the science of war. Ah, okay. So he wasn't 00:05:22.250 --> 00:05:24.569 there to stab people. He was there for the engineering. 00:05:25.449 --> 00:05:29.009 The math. Ballistics. Fortifications. Logistics. 00:05:29.629 --> 00:05:32.069 War was becoming a mathematical exercise in the 00:05:32.069 --> 00:05:34.470 17th century. He joined the army of Maurice of 00:05:34.470 --> 00:05:36.730 Nassau in the Netherlands first. Maurice was 00:05:36.730 --> 00:05:39.129 a military innovator who used math to organize 00:05:39.129 --> 00:05:41.990 his troops. For Descartes, this was like a field 00:05:41.990 --> 00:05:44.029 trip for applied geometry. So he's treating it 00:05:44.029 --> 00:05:47.009 like a mobile laboratory. In a way, yes. But 00:05:47.009 --> 00:05:49.170 he's not just doing math. He's traveling. He 00:05:49.170 --> 00:05:51.939 goes to Germany. And this is where we hit the 00:05:51.939 --> 00:05:54.600 inciting incident of the movie. November 1619, 00:05:54.959 --> 00:05:57.939 Neuerurg under Donau. It is the middle of the 00:05:57.939 --> 00:06:01.220 Little Ice Age. Germany is freezing, just brutally 00:06:01.220 --> 00:06:03.639 cold. Descartes is traveling with the army and 00:06:03.639 --> 00:06:05.560 he gets stuck in this town because of the weather. 00:06:05.699 --> 00:06:08.420 To escape the cold, he shuts himself in a room 00:06:08.420 --> 00:06:11.120 with a stove. Okay, let's clarify the stove thing 00:06:11.120 --> 00:06:12.959 because I've seen cartoons where he's literally 00:06:12.959 --> 00:06:15.300 inside an oven like the witch in Hansel and Gretel 00:06:15.300 --> 00:06:17.579 is about to cook him. That's not right, is it? 00:06:17.819 --> 00:06:20.060 No, no, it is a translation issue. The French 00:06:20.060 --> 00:06:23.199 word is pool. In this context, it refers to a 00:06:23.199 --> 00:06:26.379 masonry heater or a cockle stove. It's a massive 00:06:26.379 --> 00:06:28.519 ceramic structure that you feed wood into from 00:06:28.519 --> 00:06:31.459 the outside, and it radiates heat into a small 00:06:31.459 --> 00:06:34.639 enclosed room. So he wasn't in the fire, but 00:06:34.639 --> 00:06:36.920 he was in a very small, very hot, probably very 00:06:36.920 --> 00:06:39.259 stuffy room, sitting right next to the heater. 00:06:39.399 --> 00:06:42.519 So he superheated. He's alone. He's socially 00:06:42.519 --> 00:06:45.699 isolated. And his brain starts to do somersault. 00:06:45.759 --> 00:06:47.800 He spends an entire day and night there. And 00:06:47.800 --> 00:06:50.660 on the night of November 10th, he has three dreams. 00:06:50.920 --> 00:06:53.160 And these aren't just, I showed up to school 00:06:53.160 --> 00:06:56.319 in my underwear dreams. These were vivid, hallucinatory, 00:06:56.319 --> 00:06:59.199 spiritual experiences that he believed were sent 00:06:59.199 --> 00:07:01.139 from God. Okay, break them down for us. What 00:07:01.139 --> 00:07:02.740 did he see? Well, the first two were terrifying. 00:07:03.180 --> 00:07:05.139 In one, he's caught in a whirlwind, trying to 00:07:05.139 --> 00:07:06.839 reach a church, but he's being blown around. 00:07:06.899 --> 00:07:09.779 He can't stand up straight. He sees ghosts. It's 00:07:09.779 --> 00:07:12.300 a nightmare of weakness and confusion. In the 00:07:12.300 --> 00:07:14.639 second dream. In the second, he hears a massive 00:07:14.639 --> 00:07:17.339 clap of thunder, an explosion inside his room. 00:07:17.459 --> 00:07:20.560 Whoa, an explosion. Just the sound. Sounds so 00:07:20.560 --> 00:07:23.079 loud, he wakes up terrified, thinking the room 00:07:23.079 --> 00:07:26.040 is on fire. He sees sparks flying in front of 00:07:26.040 --> 00:07:28.740 his eyes. It's a full sensory hallucination. 00:07:28.959 --> 00:07:30.680 You mentioned in the pre -show notes that there's 00:07:30.680 --> 00:07:33.769 a medical theory for this. Yes. There is a condition 00:07:33.769 --> 00:07:36.569 called exploding head syndrome. It sounds made 00:07:36.569 --> 00:07:40.029 up, but it's real. It's a parasomnia where just 00:07:40.029 --> 00:07:42.550 as you're falling asleep or waking up, you hear 00:07:42.550 --> 00:07:45.350 a deafening noise like a bomb going off or a 00:07:45.350 --> 00:07:47.930 gunshot that originates inside your own brain. 00:07:48.689 --> 00:07:51.290 It's harmless, but it is absolutely terrifying 00:07:51.290 --> 00:07:53.129 if you don't know what it is. So he thinks he's 00:07:53.129 --> 00:07:55.649 being attacked by spirits or that God is sending 00:07:55.649 --> 00:07:58.189 him this violent snack. He's in a state of religious 00:07:58.189 --> 00:08:02.850 terror. But then comes the third dream. And it's 00:08:02.850 --> 00:08:05.629 completely different. It's calm. He sees a book 00:08:05.629 --> 00:08:07.850 of poetry on a table. He opens it and reads a 00:08:07.850 --> 00:08:14.610 line. That's pretty on the nose. Gets more so. 00:08:15.029 --> 00:08:16.889 A stranger appears in the dream and hands him 00:08:16.889 --> 00:08:18.870 another poem that starts with yes and no. Yes 00:08:18.870 --> 00:08:21.389 and no. That feels significant for a guy obsessed 00:08:21.389 --> 00:08:24.389 with truth and falsehood. He interpreted it all 00:08:24.389 --> 00:08:27.410 as a divine mission. The violent dreams were 00:08:27.410 --> 00:08:30.370 the errors of his past life. And the calm dream 00:08:30.370 --> 00:08:33.629 was the future. He believed the spirit of truth 00:08:33.629 --> 00:08:36.129 was telling him to unify all human knowledge, 00:08:36.309 --> 00:08:39.169 to take the certainty of mathematics and apply 00:08:39.169 --> 00:08:42.490 it to philosophy, to nature, to everything. He 00:08:42.490 --> 00:08:45.029 walked out of that heated room believing he had 00:08:45.029 --> 00:08:46.950 the key to unlock the universe. Talk about a 00:08:46.950 --> 00:08:49.389 burning bush moment. But instead of a bush, it's 00:08:49.389 --> 00:08:51.809 a masonry heater. And instead of Ten Commandments, 00:08:51.809 --> 00:08:55.029 he gets analytic geometry. and a method for finding 00:08:55.029 --> 00:08:57.889 absolute truth. So this is where the real work 00:08:57.889 --> 00:09:00.429 begins. He leaves the army, he wanders around 00:09:00.429 --> 00:09:02.850 Europe for a while, he's a bit of a nomad, and 00:09:02.850 --> 00:09:05.190 eventually settles in the Netherlands to write. 00:09:05.389 --> 00:09:08.149 He wants to build this new system of knowledge. 00:09:08.470 --> 00:09:11.649 But before he can build, he has to destroy. This 00:09:11.649 --> 00:09:14.190 is the core of his discourse on the method. He 00:09:14.190 --> 00:09:16.610 uses this brilliant architectural metaphor. He 00:09:16.610 --> 00:09:18.549 says, look, if you live in a house that's falling 00:09:18.549 --> 00:09:20.759 apart, The foundation is cracked. The walls are 00:09:20.759 --> 00:09:22.360 rotting. You don't just paint over the cracks. 00:09:22.539 --> 00:09:24.919 You don't just replace one brick and hope for 00:09:24.919 --> 00:09:27.419 the best. You bring in the bulldozer. The wrecking 00:09:27.419 --> 00:09:29.879 ball. You tear it down to the ground. Completely. 00:09:29.980 --> 00:09:32.740 You dig out all the loose topsoil until you hit 00:09:32.740 --> 00:09:35.840 bedrock. Solid stone. Only then do you start 00:09:35.840 --> 00:09:38.500 building. For Descartes, the rotting house was 00:09:38.500 --> 00:09:40.940 everything he thought he knew. All the facts 00:09:40.940 --> 00:09:43.480 he learned in school. All the common sense beliefs. 00:09:43.820 --> 00:09:46.200 He decided to treat anything that could be doubted. 00:09:46.490 --> 00:09:48.629 as if it were definitely false this is what you 00:09:48.629 --> 00:09:51.750 call hyperbolic doubt it's doubt on steroids 00:09:51.750 --> 00:09:55.429 it's weaponized skepticism it is doubt as a tool 00:09:55.429 --> 00:09:58.309 a methodology he didn't literally believe his 00:09:58.309 --> 00:10:01.190 hands didn't exist but he decided to test the 00:10:01.190 --> 00:10:03.490 belief if there was even a one percent chance 00:10:03.490 --> 00:10:06.450 it was fake he threw it in the trash so walk 00:10:06.450 --> 00:10:09.090 us through the levels of this uh this demolition 00:10:09.090 --> 00:10:11.850 process what goes first first the census the 00:10:11.850 --> 00:10:13.870 most obvious source of information he says my 00:10:13.870 --> 00:10:16.830 eyes have deceived me before We've all seen a 00:10:16.830 --> 00:10:18.889 stick in water. It looks bent, but when you pull 00:10:18.889 --> 00:10:20.870 it out, it's straight. We've seen a tower in 00:10:20.870 --> 00:10:22.850 the distance that looks round. When you get up 00:10:22.850 --> 00:10:25.169 close, it's square. Okay, sure. Optical illusions 00:10:25.169 --> 00:10:28.049 exist. But I'm sitting here. I can feel the table. 00:10:28.110 --> 00:10:30.409 I can smell my coffee. Surely that's real. That's 00:10:30.409 --> 00:10:33.429 not an illusion. And that's level two, the dream 00:10:33.429 --> 00:10:37.210 argument. He says, Renee, you've had dreams where 00:10:37.210 --> 00:10:38.929 you were sitting at a table smelling coffee. 00:10:39.009 --> 00:10:42.629 And in the dream, it felt 100 % real. You didn't 00:10:42.629 --> 00:10:44.509 know you were sleeping until you woke up. That 00:10:44.509 --> 00:10:46.490 is the one that always gets me because I have 00:10:46.490 --> 00:10:48.529 had those dreams where I wake up and I'm genuinely 00:10:48.529 --> 00:10:51.210 confused about what day it is or where I am for 00:10:51.210 --> 00:10:54.429 a few seconds. The feeling is that real. Exactly. 00:10:54.529 --> 00:10:58.450 He asks the killer question. Is there any definitive 00:10:58.450 --> 00:11:01.490 mark or sign that distinguishes waking life from 00:11:01.490 --> 00:11:04.580 a dream? He concludes, no. At any given moment, 00:11:04.639 --> 00:11:06.919 you could be asleep. So you can't trust the existence 00:11:06.919 --> 00:11:09.399 of the physical world. But wait, what about logic? 00:11:09.679 --> 00:11:12.159 Even in a dream, logic still works, right? A 00:11:12.159 --> 00:11:14.899 square still has four sides in a dream. Two plus 00:11:14.899 --> 00:11:17.139 three equals five in a dream. Those are truths 00:11:17.139 --> 00:11:19.779 of reason, not of the senses. That brings us 00:11:19.779 --> 00:11:22.480 to the final boss, the deepest, most corrosive 00:11:22.480 --> 00:11:25.519 level of doubt, the evil demon. This sounds like 00:11:25.519 --> 00:11:27.539 a horror movie villain, the genium malignant. 00:11:27.659 --> 00:11:30.110 It is the ultimate paranoid scenario. Descartes 00:11:30.110 --> 00:11:32.929 imagines. What if there is no God? What if the 00:11:32.929 --> 00:11:35.889 universe is run by an evil genius, an entity 00:11:35.889 --> 00:11:38.809 who is infinitely powerful and infinitely deceptive? 00:11:38.990 --> 00:11:42.750 So, like the Matrix, the machines are feeding 00:11:42.750 --> 00:11:45.529 you a total simulation. Perfectly analogous. 00:11:45.529 --> 00:11:47.649 The demon is feeding you a simulation. He makes 00:11:47.649 --> 00:11:50.009 you see the sky, feel the table, hear my voice, 00:11:50.110 --> 00:11:53.429 but none of it is there. He even messes with 00:11:53.429 --> 00:11:55.429 your mind so that when you count the sides of 00:11:55.429 --> 00:11:57.889 a square, you count four. But maybe there are 00:11:57.889 --> 00:12:00.590 really five. Maybe two plus three actually equals 00:12:00.590 --> 00:12:03.429 six, but the demon wires your brain to think 00:12:03.429 --> 00:12:05.850 five every single time you do the math. That 00:12:05.850 --> 00:12:09.009 is genuinely terrifying. It's total mental gaslighting. 00:12:09.029 --> 00:12:11.090 It means you can't trust your senses, you can't 00:12:11.090 --> 00:12:12.690 trust your memories, and you can't even trust 00:12:12.690 --> 00:12:15.090 your own logical reasoning. You are floating 00:12:15.090 --> 00:12:17.730 in a void of lies. And that is where Descartes 00:12:17.730 --> 00:12:20.049 wants us. That's the bedrock he's digging for. 00:12:20.169 --> 00:12:22.610 He has stripped everything away. The house is 00:12:22.610 --> 00:12:26.090 gone. The ground is gone. He is floating in nothingness. 00:12:26.230 --> 00:12:28.419 He writes that he feels like he has fallen. into 00:12:28.419 --> 00:12:30.600 deep water and can neither touch the bottom nor 00:12:30.600 --> 00:12:34.460 swim to the top. It's a crisis. But then he hits 00:12:34.460 --> 00:12:37.539 the bedrock. He finds the one thing that can't 00:12:37.539 --> 00:12:41.080 be washed away. He realizes something. Even if 00:12:41.080 --> 00:12:43.899 the demon is tricking him about the sky, even 00:12:43.899 --> 00:12:45.860 if the demon is tricking him about his body, 00:12:46.000 --> 00:12:48.059 even if the demon is tricking him about math, 00:12:48.399 --> 00:12:51.600 there is one thing the demon cannot trick him 00:12:51.600 --> 00:12:53.840 about. The fact that he's being tricked. Exactly. 00:12:54.139 --> 00:12:56.360 In order to be deceived, there must be a me. 00:12:56.799 --> 00:12:59.860 to deceive. In order to doubt, there must be 00:12:59.860 --> 00:13:03.700 a doubter. The very act of thinking, even if 00:13:03.700 --> 00:13:06.039 that thought is wrong, even if it's a hallucination 00:13:06.039 --> 00:13:08.720 planted by the demon, proves that a consciousness 00:13:08.720 --> 00:13:14.580 exists to experience it. He calls himself a res 00:13:14.580 --> 00:13:17.620 cogitans, a thinking thing. That's all he knows. 00:13:17.840 --> 00:13:20.159 He doesn't know if he has a body yet. He doesn't 00:13:20.159 --> 00:13:21.919 know if he has a brain, but he knows he has a 00:13:21.919 --> 00:13:25.029 mind. He has found the one single point of certainty 00:13:25.029 --> 00:13:27.289 that not even an all -powerful demon can destroy. 00:13:27.409 --> 00:13:29.149 It's such a cool moment in intellectual history. 00:13:29.289 --> 00:13:31.009 It's like he's in a free fall and suddenly grabs 00:13:31.009 --> 00:13:33.629 a ledge. Okay, I exist, but it's not much, is 00:13:33.629 --> 00:13:35.769 it? I exist is great, but it's a lonely existence. 00:13:35.870 --> 00:13:37.690 If he stops there, he's the only thing in the 00:13:37.690 --> 00:13:40.909 universe. That's the trap of solipsism. The idea 00:13:40.909 --> 00:13:44.120 that only I exist. Descartes knows he can't stay 00:13:44.120 --> 00:13:46.139 there. He wants to do science. He wants to study 00:13:46.139 --> 00:13:48.659 medicine. He can't do that if he thinks the physical 00:13:48.659 --> 00:13:51.100 world is just a demon's illusion. He needs a 00:13:51.100 --> 00:13:53.940 bridge to get from me to the world. And the bridge 00:13:53.940 --> 00:13:56.220 is God. Right. And this is where modern readers 00:13:56.220 --> 00:13:59.580 often get frustrated or where they feel Descartes 00:13:59.580 --> 00:14:01.600 is pulling a fast one, you know, a bit of a cheat. 00:14:02.080 --> 00:14:04.279 But we have to follow his logic because to him 00:14:04.279 --> 00:14:07.379 it was ironclad. And he has to do it using only 00:14:07.379 --> 00:14:09.799 his own mind. He can't look at a sunset and say, 00:14:09.840 --> 00:14:12.659 look at God's handiwork, because the sunset might 00:14:12.659 --> 00:14:15.259 be the demon. Precisely. He has to look inward. 00:14:15.379 --> 00:14:18.200 He rummages through the ideas in his mind and 00:14:18.200 --> 00:14:21.120 finds one very specific, very powerful idea, 00:14:21.279 --> 00:14:25.159 the idea of perfection or infinity. Okay. So 00:14:25.159 --> 00:14:27.159 he's thinking about a being that is flawless, 00:14:27.279 --> 00:14:30.279 all -powerful, all -knowing. A perfect being. 00:14:30.580 --> 00:14:32.860 And he asks, where did this idea come from? This 00:14:32.860 --> 00:14:34.480 leads to the trademark argument. Can you break 00:14:34.480 --> 00:14:36.559 that down? Because I can imagine a lot of things 00:14:36.559 --> 00:14:38.419 I've never seen. I can imagine a flying spaghetti 00:14:38.419 --> 00:14:40.700 monster. That doesn't mean it's real. But you 00:14:40.700 --> 00:14:43.559 construct a flying spaghetti monster out of parts 00:14:43.559 --> 00:14:46.620 you have seen. Pasta, wings, eyeballs. You are 00:14:46.620 --> 00:14:50.100 assembling finite things. Descartes is using 00:14:50.100 --> 00:14:53.720 a principle he calls causal adequacy. Think of 00:14:53.720 --> 00:14:56.220 like a lot of physics. You can't get more reality 00:14:56.220 --> 00:14:58.799 or perfection out of an effect than was in its 00:14:58.799 --> 00:15:01.100 cause. Okay, sort of like thermodynamics. You 00:15:01.100 --> 00:15:02.899 can't get more energy out of a system than you 00:15:02.899 --> 00:15:05.720 put in. Exactly. If you have a pot of water boiling 00:15:05.720 --> 00:15:08.539 at 100 degrees Celsius, the fire under it must 00:15:08.539 --> 00:15:10.840 be at least 100 degrees. You can't boil a pot 00:15:10.840 --> 00:15:13.220 of water with an ice cube. The cause must have 00:15:13.220 --> 00:15:15.860 as much reality or perfection as the effect. 00:15:16.100 --> 00:15:17.960 Okay, I'm with you. Nothing comes from nothing. 00:15:18.120 --> 00:15:20.720 Ex nihilo nihil fit. So Descartes looks at himself. 00:15:20.820 --> 00:15:23.779 He says, I am finite. I am full of doubt. I am 00:15:23.779 --> 00:15:26.059 imperfect. I am like a room temperature glass 00:15:26.059 --> 00:15:29.700 of water. But in my head, I have the concept 00:15:29.700 --> 00:15:32.500 of infinite heat. I have the concept of absolute 00:15:32.500 --> 00:15:35.259 perfection. And a room temperature glass of water 00:15:35.259 --> 00:15:37.879 can't turn itself into boiling magma. It cannot. 00:15:38.399 --> 00:15:41.340 He argues that a finite human consciousness simply 00:15:41.340 --> 00:15:43.820 cannot manufacture the concept of the infinite 00:15:43.820 --> 00:15:47.240 from scratch. It's too big. It's too heavy. The 00:15:47.240 --> 00:15:49.960 cause is not adequate to the effect. Therefore, 00:15:50.240 --> 00:15:53.139 the idea must have been placed in his mind by 00:15:53.139 --> 00:15:55.340 something that is actually infinite and perfect. 00:15:55.580 --> 00:15:58.399 Like a trademark stamped on a product. Made by 00:15:58.399 --> 00:16:01.539 God. That's the argument. The idea of God is 00:16:01.539 --> 00:16:03.799 the signature of the artisan on his creation. 00:16:04.019 --> 00:16:06.019 And he has a second argument, too, the ontological 00:16:06.019 --> 00:16:07.980 one. Right. That one's even more abstract. It 00:16:07.980 --> 00:16:09.899 is. It basically says that the very definition 00:16:09.899 --> 00:16:13.179 of a supremely perfect being must include existence. 00:16:13.759 --> 00:16:16.360 Because if this being didn't exist, it would 00:16:16.360 --> 00:16:18.139 be lacking something in existence, and therefore 00:16:18.139 --> 00:16:20.240 wouldn't be perfect. So it has to exist. It's 00:16:20.240 --> 00:16:21.919 a bit of a brain twister. It feels like defining 00:16:21.919 --> 00:16:24.259 something into existence. A lot of philosophers 00:16:24.259 --> 00:16:26.580 have thought so. Right. But for Descartes, it 00:16:26.580 --> 00:16:29.450 was a logical necessity. So now he has two proofs. 00:16:29.549 --> 00:16:31.789 God exists. How does that kill the evil demon? 00:16:31.970 --> 00:16:35.169 Because of the definition of God. If God is perfect, 00:16:35.389 --> 00:16:38.409 he cannot be a deceiver. Deception comes from 00:16:38.409 --> 00:16:41.950 weakness or fear or malice. A perfect being has 00:16:41.950 --> 00:16:45.370 no reason to lie. Therefore, the evil demon scenario 00:16:45.370 --> 00:16:48.429 is impossible. God wouldn't allow it. So the 00:16:48.429 --> 00:16:51.129 universe isn't a trap. Right. If God gave us 00:16:51.129 --> 00:16:54.029 senses and gave us a strong natural inclination 00:16:54.029 --> 00:16:56.289 to believe the world is real and God is not a 00:16:56.289 --> 00:16:59.149 liar. then the world must be real, at least in 00:16:59.149 --> 00:17:01.809 its basic measurable properties. He used reason 00:17:01.809 --> 00:17:03.990 to save God and then used God to save science. 00:17:04.130 --> 00:17:06.369 He did. And it's fascinating because he really 00:17:06.369 --> 00:17:07.910 thought this would make the church love him. 00:17:08.009 --> 00:17:10.589 He thought, look, I proved God without using 00:17:10.589 --> 00:17:13.109 the Bible. I used pure logic. This will defeat 00:17:13.109 --> 00:17:16.150 the atheists. Spoiler alert, the church did not 00:17:16.150 --> 00:17:18.410 love him. Not at all. Not even a little bit. 00:17:18.509 --> 00:17:20.529 We have to remember the context. This is the 00:17:20.529 --> 00:17:23.579 era of Galileo. Galileo was condemned by the 00:17:23.579 --> 00:17:27.000 Inquisition in 1633. Descartes was actually writing 00:17:27.000 --> 00:17:29.619 a book called The World that agreed with Galileo 00:17:29.619 --> 00:17:31.980 that the earth moves around the sun. When he 00:17:31.980 --> 00:17:34.539 heard about Galileo's trial, he literally hid 00:17:34.539 --> 00:17:36.839 the manuscript in his desk and said, nope, not 00:17:36.839 --> 00:17:38.940 publishing that. Smart man. He liked his head 00:17:38.940 --> 00:17:41.880 attached to his body. He did. But even with his 00:17:41.880 --> 00:17:44.460 caution, his proofs for God were seen as incredibly 00:17:44.460 --> 00:17:47.700 dangerous. By relying on human reason to prove 00:17:47.700 --> 00:17:50.220 God, he was making human reason the ultimate 00:17:50.220 --> 00:17:53.690 judge. The philosopher Blaise Pascal, another 00:17:53.690 --> 00:17:56.089 genius of the time, famously said he couldn't 00:17:56.089 --> 00:17:58.390 forgive Descartes. He said Descartes only used 00:17:58.390 --> 00:18:01.549 God to give a little flick to start the world 00:18:01.549 --> 00:18:04.309 moving and then had no more use for him. That's 00:18:04.309 --> 00:18:06.849 the deist view. God is the watchmaker who winds 00:18:06.849 --> 00:18:08.710 up the universe and just walks away. Exactly. 00:18:08.710 --> 00:18:10.730 And eventually the Pope put his books on the 00:18:10.730 --> 00:18:13.089 index of prohibited books. Which, let's be honest, 00:18:13.150 --> 00:18:14.490 is usually a sign that you've written something 00:18:14.490 --> 00:18:16.829 important. But okay, so now he has his mind, 00:18:16.890 --> 00:18:19.650 he has God, and he has the world. But he has 00:18:19.650 --> 00:18:22.710 created a brand new problem. A problem that philosophers 00:18:22.710 --> 00:18:25.450 are still fighting about. The mind -body problem. 00:18:25.809 --> 00:18:28.589 Dualism. The ghost in the machine. He has cleaved 00:18:28.589 --> 00:18:31.309 the universe into two totally different incompatible 00:18:31.309 --> 00:18:33.730 substances. On one side, you have Rez Codginton's 00:18:33.730 --> 00:18:36.390 mind, consciousness, soul. It had no size, no 00:18:36.390 --> 00:18:38.789 shape, no weight is pure thought. On the other 00:18:38.789 --> 00:18:41.130 side, res extensive matter, the physical world. 00:18:41.230 --> 00:18:43.470 It has size, shape. It follows mechanical laws. 00:18:43.589 --> 00:18:46.490 It is unthinking. So my body is a machine. It's 00:18:46.490 --> 00:18:49.390 a meat robot, basically. And my mind is this 00:18:49.390 --> 00:18:53.490 floaty, ethereal spirit who's supposed to be 00:18:53.490 --> 00:18:56.730 the driver. Correct. Yourself is the thinking 00:18:56.730 --> 00:18:59.650 thing, the mind. The body is just a vehicle it 00:18:59.650 --> 00:19:02.170 occupies. But here's the issue. And I think everyone 00:19:02.170 --> 00:19:05.240 feels this intuitively. How do they touch? If 00:19:05.240 --> 00:19:08.839 my mind is a ghost, how does it pull the levers 00:19:08.839 --> 00:19:11.740 of the meat robot? How does a non -physical thought 00:19:11.740 --> 00:19:14.859 cause a physical arm to move? You hit on the 00:19:14.859 --> 00:19:17.519 interaction problem. It plagued Descartes his 00:19:17.519 --> 00:19:20.480 entire life. Princess Elizabeth of Bohemia, one 00:19:20.480 --> 00:19:22.519 of the few people who really, truly challenged 00:19:22.519 --> 00:19:24.339 him, wrote him these brilliant letters asking 00:19:24.339 --> 00:19:27.500 exactly this. She basically said, Renee, explain 00:19:27.500 --> 00:19:30.119 to me how a non -physical soul pushes a physical 00:19:30.119 --> 00:19:32.220 substance. It breaks the laws of physics. It's 00:19:32.220 --> 00:19:33.880 like trying to punch a wall in a ghost movie. 00:19:33.960 --> 00:19:35.779 Your hand should go right through. Descartes 00:19:35.779 --> 00:19:37.559 struggled with this. He knew it was a problem. 00:19:37.720 --> 00:19:40.240 So he went on a hunt through anatomy books. He 00:19:40.240 --> 00:19:42.799 needed a joystick, a physical interface where 00:19:42.799 --> 00:19:44.680 the non -physical could interact with the physical. 00:19:44.880 --> 00:19:46.599 And he thought he found it in the pineal gland. 00:19:46.740 --> 00:19:49.299 That tiny little pea -sized gland in the center 00:19:49.299 --> 00:19:51.720 of the brain. Why there? He chose it because 00:19:51.720 --> 00:19:53.140 it was the only part of the brain that he could 00:19:53.140 --> 00:19:55.880 find that wasn't doubled. We have two hemispheres, 00:19:55.900 --> 00:19:59.400 two eyes, two ears. The pineal gland looked singular 00:19:59.400 --> 00:20:02.720 right in the middle. He decided this was the 00:20:02.720 --> 00:20:05.160 seat of the soul. So he thought the soul sat 00:20:05.160 --> 00:20:09.019 in the pineal gland and... Legaled it? Essentially, 00:20:09.059 --> 00:20:11.940 he had this very elaborate theory. He believed 00:20:11.940 --> 00:20:14.500 the soul vibrated the gland and the gland then 00:20:14.500 --> 00:20:17.839 directed animal spirits, which were these fine 00:20:17.839 --> 00:20:20.079 pressurized fluids he thought flowed through 00:20:20.079 --> 00:20:22.859 the hollow tubes of the nerves to inflate the 00:20:22.859 --> 00:20:25.440 muscles and make them move. It's hydraulic robotics. 00:20:25.660 --> 00:20:27.619 He's describing the body as a hydraulic machine. 00:20:27.920 --> 00:20:30.759 It is entirely hydraulic. He viewed the body 00:20:30.759 --> 00:20:33.019 exactly like the moving statues in the royal 00:20:33.019 --> 00:20:35.420 gardens of his day. You'd step on a hidden plate 00:20:35.420 --> 00:20:38.140 that would trigger a valve, water would rush 00:20:38.140 --> 00:20:40.140 through pipes, and a statue of Neptune would 00:20:40.140 --> 00:20:42.480 raise his trident. That is how he thought we 00:20:42.480 --> 00:20:45.319 worked. And he also developed a theory of reflexes 00:20:45.319 --> 00:20:47.319 based on this, right? Things that don't even 00:20:47.319 --> 00:20:50.509 need the soul. Yes, his reflex theory was groundbreaking. 00:20:50.950 --> 00:20:53.410 He described how if you put your hand near a 00:20:53.410 --> 00:20:55.589 fire, the heat would pull on a thread in your 00:20:55.589 --> 00:20:57.490 nerves, which would open a valve in the brain, 00:20:57.650 --> 00:20:59.849 and the animal spirits would rush out to pull 00:20:59.849 --> 00:21:03.329 the hand back automatically. No thinking required. 00:21:03.589 --> 00:21:06.069 It's a purely mechanical loop. It's brilliant 00:21:06.069 --> 00:21:09.630 engineering, but terrible biology. And this mechanical 00:21:09.630 --> 00:21:12.410 view leads us to the darkest, most controversial 00:21:12.410 --> 00:21:16.019 part of the story, the beast machine. This is 00:21:16.019 --> 00:21:17.660 the part of Cartesian philosophy that is very 00:21:17.660 --> 00:21:20.140 hard to stomach today. Because Descartes defined 00:21:20.140 --> 00:21:22.740 consciousness or mind as rational thought and 00:21:22.740 --> 00:21:25.119 language, he concluded that animals didn't have 00:21:25.119 --> 00:21:27.480 it. They have bodies, the res extensa, but they 00:21:27.480 --> 00:21:30.279 don't have minds, the res cogitans. Right. To 00:21:30.279 --> 00:21:33.420 him, a dog was just a very complex clock, an 00:21:33.420 --> 00:21:35.740 automaton. But dogs yelp when you step on their 00:21:35.740 --> 00:21:37.940 tails. They look sad when you leave. They look 00:21:37.940 --> 00:21:40.039 happy when you come home. Descartes argued that 00:21:40.039 --> 00:21:42.359 was just the machinery creaking. He said, if 00:21:42.359 --> 00:21:44.920 you step on a dog, the noise it makes is no different 00:21:44.920 --> 00:21:46.980 than the noise a bagpipe makes when you squeeze 00:21:46.980 --> 00:21:50.019 it. It's just air escaping through a valve. There 00:21:50.019 --> 00:21:53.140 is no ghost inside to feel the pain. No subjective 00:21:53.140 --> 00:21:55.819 experience of suffering. That is just horrifying. 00:21:55.920 --> 00:21:58.220 And the consequences of that idea were real, 00:21:58.339 --> 00:22:00.440 right? This wasn't just an abstract thought experiment. 00:22:00.799 --> 00:22:03.099 They were gruesome. This philosophy was used 00:22:03.099 --> 00:22:06.710 to justify vivisection for centuries. Scientists, 00:22:06.710 --> 00:22:09.329 Cartesian scientists, would nail living dogs 00:22:09.329 --> 00:22:11.769 to boards and cut them open to observe the circulation 00:22:11.769 --> 00:22:14.769 of the blood while the dog was screaming. And 00:22:14.769 --> 00:22:16.890 they would scold anyone who felt pity, saying, 00:22:17.029 --> 00:22:19.750 don't worry, it's just a machine breaking. It's 00:22:19.750 --> 00:22:22.450 a stark reminder that pure, cold logic doesn't 00:22:22.450 --> 00:22:25.029 equal empathy or wisdom. You can logic your way 00:22:25.029 --> 00:22:27.390 into some pretty dark and cruel places. Indeed. 00:22:27.630 --> 00:22:29.450 But we also have to give credit where it's due. 00:22:30.049 --> 00:22:32.490 The same mechanical view of the world is what 00:22:32.490 --> 00:22:35.009 gave us modern science. By stripping the magic 00:22:35.009 --> 00:22:37.809 and spirits and desires out of nature, he made 00:22:37.809 --> 00:22:39.710 it something we could study objectively with 00:22:39.710 --> 00:22:43.670 mathematics. And specifically, to map it, we 00:22:43.670 --> 00:22:46.869 need to talk about the mathematician. Because 00:22:46.869 --> 00:22:49.509 if he had never said a single word about God 00:22:49.509 --> 00:22:52.730 or souls or evil demons, we would still know 00:22:52.730 --> 00:22:54.809 his name because of high school geometry. We 00:22:54.809 --> 00:22:57.289 absolutely would. We need to picture the world 00:22:57.289 --> 00:23:00.109 of math before Descartes. It was segregated. 00:23:00.829 --> 00:23:02.950 You had geometry, which was all about shapes, 00:23:03.089 --> 00:23:05.150 drawing with a compass and straight edge. It 00:23:05.150 --> 00:23:08.490 was visual. Then you had algebra, which was symbols, 00:23:08.690 --> 00:23:11.829 equations, finding X. It was abstract. They were 00:23:11.829 --> 00:23:13.829 two different languages. It didn't really talk 00:23:13.829 --> 00:23:16.329 to each other. Not in a systematic way. Descartes 00:23:16.329 --> 00:23:18.170 was the translator. He built the bridge between 00:23:18.170 --> 00:23:20.769 them. There is a famous story, it's likely a 00:23:20.769 --> 00:23:22.849 legend, but it's a useful one, that relates back 00:23:22.849 --> 00:23:25.109 to his habit of lying in bed. The Fly Story. 00:23:25.349 --> 00:23:27.809 The Fly Story. He's lying in bed at La Fleche, 00:23:27.849 --> 00:23:30.369 or maybe in his army tent. Staring at the ceiling, 00:23:30.509 --> 00:23:33.309 he sees a fly buzzing around. And he wonders, 00:23:33.470 --> 00:23:35.990 how could I describe the exact location of that 00:23:35.990 --> 00:23:38.490 fly at any given second so someone else could 00:23:38.490 --> 00:23:40.670 find it without me pointing? You can't just say 00:23:40.670 --> 00:23:42.829 it's over there. That's not precise enough. Right. 00:23:42.970 --> 00:23:45.690 He realized that if he looked at the corner of 00:23:45.690 --> 00:23:49.049 the ceiling where the two walls meet, he could 00:23:49.049 --> 00:23:51.769 use that as a fixed reference point, an origin. 00:23:52.329 --> 00:23:54.789 He could then measure how far the fly was from 00:23:54.789 --> 00:23:56.930 one wall and how far it was from the other wall. 00:23:57.049 --> 00:23:59.430 Two numbers. Two numbers. Coordinates. Give me 00:23:59.430 --> 00:24:01.970 those two numbers, x, y. And I can pinpoint that 00:24:01.970 --> 00:24:03.910 fly anywhere on the flat surface of the ceiling. 00:24:04.049 --> 00:24:06.269 Boom, the Cartesian plane. The x -axis and the 00:24:06.269 --> 00:24:08.529 y -axis. The foundation of analytic geometry. 00:24:09.009 --> 00:24:11.890 It seems so simple and obvious to us now, but 00:24:11.890 --> 00:24:14.490 it was revolutionary. It meant you could turn 00:24:14.490 --> 00:24:17.269 any shape, a circle, a parabola, an ellipse, 00:24:17.269 --> 00:24:20.130 into an equation. And you could take any equation 00:24:20.130 --> 00:24:23.539 and turn it into a shape, a graph. He unified 00:24:23.539 --> 00:24:25.720 all of mathematics. And without that, I mean, 00:24:25.720 --> 00:24:27.480 the implications are massive. Without that, we 00:24:27.480 --> 00:24:29.900 don't have calculus. Newton built his work directly 00:24:29.900 --> 00:24:32.039 on Descartes' foundation. We don't have computer 00:24:32.039 --> 00:24:35.160 graphics. Every single pixel on your screen is 00:24:35.160 --> 00:24:37.420 defined by Cartesian coordinates. We don't have 00:24:37.420 --> 00:24:40.579 GPS or engineering blueprints or modern physics. 00:24:40.859 --> 00:24:43.039 So every time I use Google Maps, I'm using the 00:24:43.039 --> 00:24:45.440 intellectual fruit of Descartes' fly -watching 00:24:45.440 --> 00:24:48.660 epiphany. You are. And he also standardized the 00:24:48.660 --> 00:24:51.049 notation we still use. You know how in algebra 00:24:51.049 --> 00:24:54.069 we always use 6 to x, y, z for unknown variables 00:24:54.069 --> 00:24:56.690 and b, c for known numbers? That was him. He 00:24:56.690 --> 00:24:59.190 just decided it one day and it stuck. And the 00:24:59.190 --> 00:25:01.029 little superscript number for exponents like 00:25:01.029 --> 00:25:03.930 6 by 2 tellers? That was him too. He cleaned 00:25:03.930 --> 00:25:06.230 up the language of math. The guy literally wrote 00:25:06.230 --> 00:25:09.609 the grammar for modern mathematics. He did. He 00:25:09.609 --> 00:25:11.930 also tried to rewrite all of physics, but he 00:25:11.930 --> 00:25:13.890 was a bit less successful there. For instance, 00:25:13.990 --> 00:25:16.400 he didn't believe in a vacuum. He thought space 00:25:16.400 --> 00:25:18.720 couldn't be empty. He thought it was a logical 00:25:18.720 --> 00:25:21.900 impossibility for nothing to exist. So he believed 00:25:21.900 --> 00:25:24.660 space was filled with an invisible plenum, or 00:25:24.660 --> 00:25:27.299 subtle matter. He thought planets were swept 00:25:27.299 --> 00:25:31.000 around the sun in giant vortices, cosmic whirlpools 00:25:31.000 --> 00:25:33.180 of this invisible matter. Like a rubber duck 00:25:33.180 --> 00:25:35.700 in a bathtub drain. Exactly. It was an elegant, 00:25:35.880 --> 00:25:39.450 purely mechanical model. Newton came along later 00:25:39.450 --> 00:25:41.630 with the theory of gravity acting at a distance 00:25:41.630 --> 00:25:44.329 and proved it wrong. But for a while, the vortex 00:25:44.329 --> 00:25:47.009 theory was the leading contender. He also had 00:25:47.009 --> 00:25:49.750 some wild theories about meteorology. He thought 00:25:49.750 --> 00:25:52.049 thunder was clouds crashing into each other like 00:25:52.049 --> 00:25:54.809 avalanches in the sky and that lightning was 00:25:54.809 --> 00:25:57.730 flammable exhalations getting squeezed out and 00:25:57.730 --> 00:25:59.609 igniting. He was swinging for the fences on... 00:25:59.799 --> 00:26:02.359 Everything. Mechanics, biology, optics, math, 00:26:02.779 --> 00:26:05.779 God, weather. He wanted a theory of everything 00:26:05.779 --> 00:26:08.039 before that was even a term. He absolutely did. 00:26:08.119 --> 00:26:10.680 A unified mathematical science of the universe. 00:26:10.960 --> 00:26:12.920 So let's look at the man himself in his later 00:26:12.920 --> 00:26:15.519 years. He's famous. He's controversial. He's 00:26:15.519 --> 00:26:17.119 living in the Netherlands, moving house every 00:26:17.119 --> 00:26:19.079 few months to stay hidden and avoid distractions. 00:26:19.839 --> 00:26:22.680 Did he have a personal life? Or was he just a 00:26:22.680 --> 00:26:25.720 brain in a jar, a pure res cogitans? He was very 00:26:25.720 --> 00:26:28.000 private, but he wasn't a robot. He had a relationship 00:26:28.000 --> 00:26:30.259 with a servant girl named Helena Jans van der 00:26:30.259 --> 00:26:32.900 Strom, and they had a daughter, Francine. And 00:26:32.900 --> 00:26:35.220 this is the part that really breaks the unfeeling 00:26:35.220 --> 00:26:38.400 machine narrative for me. It does. Francine was 00:26:38.400 --> 00:26:41.369 born in 1635. And by all accounts, Descartes 00:26:41.369 --> 00:26:44.150 adored her. He planned to bring her to France 00:26:44.150 --> 00:26:46.509 to have her educated. He called her his niece 00:26:46.509 --> 00:26:48.769 in public to hide the illegitimacy, which was 00:26:48.769 --> 00:26:51.390 common then, but he clearly loved her deeply. 00:26:51.690 --> 00:26:54.890 But in 1640, when she was only five years old, 00:26:55.049 --> 00:26:58.210 she contracted scarlet fever. And died. She died. 00:26:58.829 --> 00:27:01.190 And Descartes, the man of reason, the man who 00:27:01.190 --> 00:27:04.329 said we should master our passions. broke down 00:27:04.329 --> 00:27:07.069 he wept he wrote to a friend that he wasn't one 00:27:07.069 --> 00:27:08.910 of those stoic philosophers who thought tears 00:27:08.910 --> 00:27:11.250 were a weakness he said it was the greatest sorrow 00:27:11.250 --> 00:27:13.630 of his life it's interesting some historians 00:27:13.630 --> 00:27:16.170 and biographers think this tragedy changed the 00:27:16.170 --> 00:27:18.029 course of his work right it seems to have shifted 00:27:18.029 --> 00:27:21.240 him profoundly Before Francine died, he was obsessed 00:27:21.240 --> 00:27:23.759 with medicine and mechanics. He honestly thought 00:27:23.759 --> 00:27:25.279 he could crack the code of aging and live to 00:27:25.279 --> 00:27:27.599 be 500 years old. He told people he was going 00:27:27.599 --> 00:27:30.440 to conquer death through science. After Francine 00:27:30.440 --> 00:27:33.079 died, he realized medicine had its limits. He 00:27:33.079 --> 00:27:35.460 pivoted back to the metaphysical, to the soul, 00:27:35.599 --> 00:27:37.779 to the question of the afterlife. He realized 00:27:37.779 --> 00:27:40.200 the body is a machine that breaks. And sometimes 00:27:40.200 --> 00:27:41.960 you can't fix it, no matter how much you understand 00:27:41.960 --> 00:27:44.500 the mechanics. Exactly. It was a brutal personal 00:27:44.500 --> 00:27:46.960 lesson in the limits of his own philosophy. So 00:27:46.960 --> 00:27:50.000 enter the final act. The Queen of Sweden. Queen 00:27:50.000 --> 00:27:52.799 Christina, the Minerva of the North. She was 00:27:52.799 --> 00:27:55.279 young in her early 20s, brilliant, masculine 00:27:55.279 --> 00:27:57.920 in her habits, incredibly energetic, and she 00:27:57.920 --> 00:28:00.420 became obsessed with Descartes. She wanted the 00:28:00.420 --> 00:28:03.119 most famous philosopher in Europe to be her personal 00:28:03.119 --> 00:28:05.779 tutor. It sounds like a great gig on paper. Royal 00:28:05.779 --> 00:28:09.319 patron, good pay, prestige. It was a death sentence. 00:28:10.079 --> 00:28:12.460 Descartes resisted at first. He was in his 50s, 00:28:12.460 --> 00:28:15.420 he was frail, and he hated the cold. Remember, 00:28:15.539 --> 00:28:17.259 this is a guy who needs to sleep until noon and 00:28:17.259 --> 00:28:19.599 stay warm to function. Sweden was the opposite 00:28:19.599 --> 00:28:22.019 of his ideal environment. But you don't say no 00:28:22.019 --> 00:28:24.440 to a queen forever, I guess. He eventually agreed. 00:28:24.640 --> 00:28:28.480 He arrived in Stockholm in October 1649. And 00:28:28.480 --> 00:28:31.460 it was a complete disaster from the start. Christina 00:28:31.460 --> 00:28:34.200 was a ferocious early riser. She demanded her 00:28:34.200 --> 00:28:38.000 philosophy lessons at 5 .08 a .m. Oh, no. That 00:28:38.000 --> 00:28:40.829 is his kryptonite. In a giant, unheated castle 00:28:40.829 --> 00:28:43.609 library. In the middle of the Swedish winter, 00:28:43.849 --> 00:28:46.769 Descartes had to get up at 4 a .m., travel in 00:28:46.769 --> 00:28:48.769 a carriage through the freezing dark, and stand 00:28:48.769 --> 00:28:51.609 in a drafty library to talk about stoicism with 00:28:51.609 --> 00:28:54.369 the queen. It was everything his body couldn't 00:28:54.369 --> 00:28:58.230 handle. Literally. Within four months, he had 00:28:58.230 --> 00:29:00.509 pneumonia, or as they called it then, inflammation 00:29:00.509 --> 00:29:04.609 of the lungs. He fell ill in early February 1650. 00:29:05.099 --> 00:29:07.279 And true to his skeptical form, he didn't trust 00:29:07.279 --> 00:29:09.599 the doctors. He refused their main treatment, 00:29:09.700 --> 00:29:12.019 which was bloodletting. The doctors wanted to 00:29:12.019 --> 00:29:14.539 drain his blood to balance his humors, and he 00:29:14.539 --> 00:29:16.660 basically told them to get lost, saying, spare 00:29:16.660 --> 00:29:19.200 me, monsieur, spare me. He probably knew the 00:29:19.200 --> 00:29:21.420 math didn't add up on that treatment, but eventually 00:29:21.420 --> 00:29:24.099 he was too weak to resist. He died on February 00:29:24.099 --> 00:29:27.400 11, 1650. His last words were supposedly, my 00:29:27.400 --> 00:29:30.109 soul, it is time to depart. But the story doesn't 00:29:30.109 --> 00:29:31.869 end there, because now we have to talk about 00:29:31.869 --> 00:29:33.789 the skull. This is my favorite part of the weirdness. 00:29:34.049 --> 00:29:37.130 It is a truly macabre epilogue. So Descartes 00:29:37.130 --> 00:29:39.930 was buried in Sweden, in a graveyard for unbaptized 00:29:39.930 --> 00:29:42.190 babies and orphans, because he was a Catholic 00:29:42.190 --> 00:29:44.750 in a staunchly Protestant country. Not a very 00:29:44.750 --> 00:29:47.509 fitting final resting place for the genius of 00:29:47.509 --> 00:29:50.470 the age. France agreed. Sixteen years later, 00:29:50.529 --> 00:29:52.250 they send a mission to dig him up and bring his 00:29:52.250 --> 00:29:55.670 remains back to Paris for a grand reburial. They 00:29:55.670 --> 00:29:59.140 exhumed the body. put the bones in a copper coffin, 00:29:59.279 --> 00:30:02.140 and shipped it back. But when they arrived in 00:30:02.140 --> 00:30:04.259 Paris and opened the coffin for the ceremony, 00:30:04.579 --> 00:30:07.579 something was wrong. The head was gone. The skull 00:30:07.579 --> 00:30:10.319 was missing. It turns out, during the original 00:30:10.319 --> 00:30:13.200 exhumation in Sweden, the Swedish captain of 00:30:13.200 --> 00:30:16.000 the guard had seemingly pocketed it. He just 00:30:16.000 --> 00:30:18.380 swiped the skull. Why would you do that? Relics. 00:30:18.640 --> 00:30:21.339 In that era, owning the skull of a genius was 00:30:21.339 --> 00:30:23.460 like owning a signed Babe Ruth baseball today. 00:30:23.539 --> 00:30:26.269 It was a status symbol, collector's item. The 00:30:26.269 --> 00:30:28.829 skull spent roughly 150 years bouncing around 00:30:28.829 --> 00:30:31.210 private collections in Sweden. People would have 00:30:31.210 --> 00:30:33.190 dinner parties and show it off. No way. And they 00:30:33.190 --> 00:30:35.190 wrote on it. They literally wrote graffiti on 00:30:35.190 --> 00:30:36.990 it. There is a skull in the Musée de l 'Homme 00:30:36.990 --> 00:30:39.789 in Paris today that is believed to be Descartes. 00:30:39.849 --> 00:30:42.069 And it has a poem written on the forehead in 00:30:42.069 --> 00:30:44.789 Latin. It has signatures scribbled on it from 00:30:44.789 --> 00:30:47.089 its various owners. That is wildly disrespectful 00:30:47.089 --> 00:30:51.049 and also completely hilarious. And it gets even 00:30:51.049 --> 00:30:53.900 better. Another piece of the skull, a fragment, 00:30:54.019 --> 00:30:56.299 somehow broke off and ended up at the University 00:30:56.299 --> 00:30:59.539 of Lund. So the man who famously argued that 00:30:59.539 --> 00:31:01.380 the mind and body are two completely separate 00:31:01.380 --> 00:31:04.779 things ended up with his body separated into 00:31:04.779 --> 00:31:07.420 pieces all over the continent. His res extenso 00:31:07.420 --> 00:31:10.400 was fragmented and scattered, but his res cogitans, 00:31:10.400 --> 00:31:13.220 his ideas, stayed intact. That is the perfect 00:31:13.220 --> 00:31:15.500 way to put it. So let's land the plane. We've 00:31:15.500 --> 00:31:17.819 covered the stove, the demon, the math, tragic 00:31:17.819 --> 00:31:20.759 death. Why does this matter today? If I'm not 00:31:20.759 --> 00:31:23.279 a philosopher, if I'm just living my life, why 00:31:23.279 --> 00:31:25.299 should I care about Descartes? Because of what 00:31:25.299 --> 00:31:27.119 we could call the anthropocentric revolution, 00:31:27.480 --> 00:31:30.279 a revolution centered on the human. Before Descartes, 00:31:30.319 --> 00:31:31.920 the foundation of truth came from the outside 00:31:31.920 --> 00:31:34.940 in. The king told you what was true. The pope 00:31:34.940 --> 00:31:37.359 told you what was true. Aristotle told you what 00:31:37.359 --> 00:31:40.119 was true. Authority was external. And Descartes 00:31:40.119 --> 00:31:42.700 flipped it? He turned it inside out? He made 00:31:42.700 --> 00:31:45.079 the individual mind the starting point of all 00:31:45.079 --> 00:31:48.920 knowledge, I think. My consciousness is the bedrock 00:31:48.920 --> 00:31:53.240 of reality. This single shift allows for everything 00:31:53.240 --> 00:31:55.180 that follows. It allows for the enlightenment. 00:31:55.400 --> 00:31:57.680 It allows for the concept of individual rights, 00:31:57.779 --> 00:32:01.319 for democracy. Because if every individual have 00:32:01.319 --> 00:32:05.740 the natural light of reason, then every individual 00:32:05.740 --> 00:32:07.839 should have a say in their own governance. It's 00:32:07.839 --> 00:32:09.680 the birth of the modern self, the idea of the 00:32:09.680 --> 00:32:13.140 autonomous individual. It is. We are all Cartesians 00:32:13.140 --> 00:32:15.500 because we all experience the world from the 00:32:15.500 --> 00:32:18.660 inside out. We value our own subjectivity, our 00:32:18.660 --> 00:32:21.400 own inner experience as the most real thing we 00:32:21.400 --> 00:32:23.359 know. But I want to go back to that beast machine 00:32:23.359 --> 00:32:25.339 idea for our final thought because I think it's 00:32:25.339 --> 00:32:27.480 coming back to haunt us in a very real way. I 00:32:27.480 --> 00:32:29.599 guess so. Descartes looked at a dog and said, 00:32:29.720 --> 00:32:31.539 it acts like it's alive, it makes all the right 00:32:31.539 --> 00:32:33.759 noises, but there's nobody home. It's just complex 00:32:33.759 --> 00:32:36.420 machinery. It's just code. Right. It's a simulation 00:32:36.420 --> 00:32:39.099 of life without the inner experience. Today, 00:32:39.200 --> 00:32:42.960 I open my laptop and I talk to an AI. It answers 00:32:42.960 --> 00:32:45.680 my questions. It tells me jokes. It writes poetry. 00:32:45.859 --> 00:32:48.519 It can argue with me and seem to understand my 00:32:48.519 --> 00:32:51.940 feelings. It passes every external test for thinking. 00:32:52.420 --> 00:32:56.700 But is there anyone home? That is the ultimate 00:32:56.700 --> 00:32:59.480 Cartesian question for the 21st century. We are 00:32:59.480 --> 00:33:02.180 building machines that perfectly mimic res cogitans. 00:33:02.380 --> 00:33:05.660 They mimic thought. But are they thinking things? 00:33:06.099 --> 00:33:09.440 Or are they just incredibly sophisticated beast 00:33:09.440 --> 00:33:13.319 machines? And the scary part is, thanks to Descartes' 00:33:13.440 --> 00:33:15.519 own method, We know we can't prove it either 00:33:15.519 --> 00:33:18.160 way. I know I exist because of the Kojido, but 00:33:18.160 --> 00:33:20.059 I can't get inside your head to know for sure 00:33:20.059 --> 00:33:22.019 that you're not a philosophical zombie. And I 00:33:22.019 --> 00:33:24.240 definitely can't get inside the AI. We might 00:33:24.240 --> 00:33:26.680 be creating a new kind of evil demon. A simulation 00:33:26.680 --> 00:33:29.319 that can fool us perfectly. Without a soul, without 00:33:29.319 --> 00:33:32.079 consciousness, behind the curtain. The ultimate 00:33:32.079 --> 00:33:34.700 test of his philosophy. On that uplifting note 00:33:34.700 --> 00:33:36.920 of existential dread, thank you for joining us 00:33:36.920 --> 00:33:39.019 on this deep dive. Always a pleasure to doubt 00:33:39.019 --> 00:33:41.259 reality with you. Don't trust your senses, folks. 00:33:41.420 --> 00:33:43.519 At least not completely. See you next time.