▶︎ 0:00 We're beginning with Rene Descartes and his Meditations on First Philosophy, which is undoubtedly one of the most important books in philosophy, but really one of the most important books in the history of Western civilization. And it's based on the events that happened to him on a snowy evening, in November, on November 10th in 1619 when he was alone in this cabin and he started thinking about knowledge, which is our topic.
▶︎ 0:36 Descartes, of course, was very brilliant, and he had the best education that was available at the time. He studied in the best schools, learned everything there was to know at the time, and he came out of it very disappointed with his education, because he felt that all of it could be questioned. None of it was certain, none of it was solid. But most importantly, none of the things that he learned did what he thought education should do, what he thought knowledge should do, which was help us live better.
▶︎ 1:14 He felt that the way that people were learning at the time, the body of knowledge that had been accumulated that was considered, that there was a consensus on, it didn't help, it wasn't in the service of human life. We couldn't cure diseases. We didn't have machines that could transport us more quickly, that could connect us by communication. We didn't have good medicine. All of these things that would make life better, the kinds of education that they had at the time was useless for.
▶︎ 1:52 And what he decided was to change that. It's extraordinarily audacious, but he decided that he was going to start science anew. He was going to reboot Western civilization. He was gonna stop where they were and start it back from the beginning, start from scratch and put us on the right path now. He was going to create science in a way that it had not been before, so that it could give us these benefits.
▶︎ 2:29 And we have to realize now just how different things were in the early 17th century than they are now. When we think about how to do science, it seems quite obvious to us. You put on a white coat, you do some experiments, you make some observations, you have a hypothesis, you test it. This is all very, very obvious to us. But that's only because we've been learning this our whole lives, because we have centuries now of successful science, of a body of knowledge that has been accumulating, of scientists who have been refining this method now for hundreds of years with success, with technology coming out that establishes how productive it is.
▶︎ 3:20 But the reason why we have this is precisely because of thinkers like Descartes, because of books like this. Science began at a certain moment. It's a human creation. It's not a thing that we found. It's a method that we made, which means someone had to make it, and the person who made it, obviously, if you make it, it wasn't there before. And he didn't know how to do science.
▶︎ 3:50 Even afterwards, Isaac Newton, arguably the greatest scientist who ever lived, when we went through his papers afterwards, what we found was that the amount he wrote on science... This is the man who discovered the law of gravity, who pulled apart the rainbow to understand how light works. There was 10 times as much writing about alchemy and Biblical prophecy than there was about science, because it just wasn't known what kinds of things could produce reliable knowledge at that time. They didn't know how to do it. And so Descartes is starting from nothing, and he has to create a way to know things,
▶︎ 4:42 But if you don't yet know how to know things, then you can't know how to know that. And he can't just start by observing. That seems like a pretty obvious place to start. Just look around, make some observations. That's how we were taught in eighth grade when we did experiments on potatoes. You'd just make some observations. Well, you can't just start by opening your eyes and looking at the world. It's not that simple.
▶︎ 5:14 To explain that, let me give you a thought experiment. Imagine you wake up very early in the morning and you go climb a mountain and you look to the east and the horizon starts brightening. And what would you say that you see? You would probably say that. And if someone pressed you on that, "Exactly what do you mean you see the sunrise?" You say, "Well, of course, it's not the sun actually rising. What I'm seeing is the effect of the rotation of the Earth, that is lowering the horizon and revealing the sun there."
▶︎ 5:55 But if we could time bring someone from the 12th century there, a 12th century farmer to stand next to you and look at the exact same thing, look at the horizon at 6:00 in the morning from the mountain, and ask them what they see. They would say they see the sun rise, but they would mean it literally. They would say they see the sun actually moving up the sky, not the earth moving. And the question is, the philosophical question is, are the two of you seeing the same thing or not?
▶︎ 6:33 Now, in a very straightforward, simple sense, of course you are. The same photons hitting your retinas at the same time. But in another very important sense, you're not seeing the same thing at all. What you are seeing is the light through a conceptual lens. The conceptual lens being a heliocentric model of the solar system. Meaning, you think the sun is in the center of the solar system and the earth is turning on its axis while rotating around the sun. And that's why you would think that you see what you see. You see the earth rotating and the sun being revealed.
▶︎ 7:20 Whereas the 12th century farmer, we'll just call her Frida. She would say that she sees things through the lens of a geocentric universe, meaning the earth is at the center, and the sun moves around it. So when she sees the same thing, the same light coming up, she is seeing it through these ideas, through these beliefs. The beliefs are shaping what she sees just as much as your beliefs are shaping what you see.
▶︎ 7:58 We think that all we do is open up our eyes and we just see the world, unmediated, here it is, presented to us. But in fact, our experience, our perceptions are always mediated through beliefs, through ideas, through other things that we think. And so, we say that seeing is believing, but in a very important sense, believing is seeing. What you believe determines what you will see, what you understand, what you see to mean.
▶︎ 8:41 Descartes couldn't just start collecting observations. Because if you have the wrong beliefs, if you have the wrong framework within which you are putting these perceptions, then you're going to be interpreting them incorrectly. You're going to be seeing the wrong thing. Frida was making the same observations as you were when she looked to the east, but she was seeing, we would say, the wrong thing, because she held other beliefs that were incorrect.
▶︎ 9:15 Descartes feels that before even he could start looking, before he could start forming hypotheses, before he can do anything like that, he has to make sure that the framework that he has, the conceptual framework, the overall view of the universe that he has, is right. Because if it's wrong, then everything that gets filtered through that is going to be distorted. Everything that he sees or thinks that's based on that will be wrong. So before he goes tinkering with this belief or that belief, before he goes looking at this object or that object, first he has to get his entire worldview correct.
▶︎ 10:07 And that's really hard, because it's the entire worldview that tells us how to do anything, including how to fix that worldview. Even trying to correct the worldview to create the right worldview is itself affected by the worldview that you have. So it's incredibly hard to break out of this. And if you don't, if you can't break out of it and make sure the one that you have is right, then nothing else you do can be certain. Everything else you do is going to be suspect, because it could all be seeing the sun rise instead of seeing the earth rotate. And this is what Descartes undertook to do.
▶︎ 11:01 Descartes decided that he was going to get all the way down. He had to get beneath these frameworks, under them to the absolute bottom-most layer. And he had to get ideas to build what he called his foundation. His foundation, this was the analogy he uses throughout the book, this building foundation. His foundation had to be absolutely solid, absolutely certain.
▶︎ 11:31 So there were these beliefs that he put in his foundation, where he began from, they had to be so true. They weren't just true, they were so true they could not be false. Now, think about that. There are a lot of true beliefs. There are a lot of beliefs that I have that are true, but they could be false. They could be false. They might be wrong. I've been wrong about quite a lot of things.
▶︎ 11:59 He wants to find ideas that are so right that no matter what, they must be true. Incredibly difficult. But it has to be that way so that he can be sure he's starting from the right beginning. It's like in operating rooms. If you open up a person's body, they're very, very susceptible then. And so if any germs get in there, then the person could get very, very ill.
▶︎ 12:33 And so if you ever see the surgeons scrub their hands in this ridiculously extreme way for 10, 20 minutes, that's what he's doing to his mind. He's gonna scrub it of every little bitty possible germ of possible error that he can find, and get down to a perfectly pristinely sterile epistemological environment where he can start and he knows there are no germs. He knows there's no infection. And then, whatever he builds from there, he can rely on. So this is what he's doing in his cabin.
▶︎ 13:10 On the snowy evening in November of 1619, and he writes it up in this book, The Meditations, and he takes us along with him. It's wonderfully written because he's not just reporting his conclusions. He's showing us the journey and he's taking us along with him, and we are meant to think these things through with him, to question the ideas ourselves as he goes along.
▶︎ 13:41 We'll start with the first meditation. He's looking for beliefs for his foundation, and his standards are ridiculously, absurdly high, have to be completely, absolutely true in any circumstances, under any conditions whatsoever, no matter what else. He only wants this once to get the foundation and then he can trust this. This isn't the way he's gonna do science for the rest of his life. It's just the way he's gonna begin to figure out how to do science. But how is he gonna find these beliefs?
▶︎ 14:20 How do you find things like that? Well, think about how you would find a material that's bulletproof. You wanna find something that is bulletproof, like Kevlar. How would you find it? You would put a whole lot of materials around a watermelon or something, and you'd shoot them. And if the bullet goes through, it's not bulletproof. There you go, that fails. Shoot another, bullet goes through, the bullet goes through, it's not bulletproof. And you would keep shooting materials until you found one that repelled the bullet, and repels the bullet, there you go, that's bulletproof.
▶︎ 15:01 That's what he's gonna do to his beliefs. He's going to try to find ways in which they're false. He's gonna try to find any possible way in which they might be false. He's not going to prove them false. The point isn't that the beliefs he has are false. The point is that the beliefs he has might be false. He has to find a belief that cannot be false, that is indubitable. That means it cannot be doubted. There are no grounds for doubt at all. There's no way you can doubt it. That's how true it is.
▶︎ 15:47 And so, like the bulletproof material, he's gonna try to doubt everything. He's gonna go through all his beliefs and try to find ways in which they might be false. Anything he can think of, any scenario, no matter how bizarre, no matter how weird, no matter how unlikely. If he can find some way that it might be false, some universe, some situation where it could be false, then he's gonna put it aside, not because it's wrong, but because it can't go into the foundation. The foundation has to be absolutely true, and if something's dubious and it might be false under any conditions, then it's not indubitable.
▶︎ 16:30 And remember, he doesn't know what the universe is like. He doesn't know if it's heliocentric or geocentric, and that goes for everything. He doesn't wanna make any assumptions whatsoever. So he's going to perform what
▶︎ 16:47 has come to be called methodological doubt. That means it's not organic, natural doubt. It's not because he actually wonders if these things are true or not. He's intentionally trying to doubt them. He's intentionally coming up with situations in which he will find or create or manufacture doubt so that then those beliefs will be set aside. He might come back to them later, but for now, they won't go into his foundation.
▶︎ 17:17 And he's gonna do that for everything he believes, everything, every little belief, until he finds something that propels the doubt and that will go in his foundation, if he can find anything. Doesn't seem possible. The rest of the first meditation is his attempt to doubt all of his beliefs, his implementing this methodological doubt.
▶︎ 17:50 Now, he has one more rule that will help this go a little faster because he has a whole lot of beliefs. We all have a lot of beliefs. I believe this shirt is blue. I believe the sun is shining. I believe... I have a lot of beliefs. If I had to go through them one by one, it would take forever. But if I can group them into groups and doubt them as a group, then it could go a lot faster.
▶︎ 18:15 And the way he groups them is by their source, where the beliefs come from, what they are based on. If he can show that a group of beliefs derives from one particular source, and he can show that that source is dubious, then he can set all those beliefs aside, that whole group that comes from it. And that simplifies his work quite a bit. So the rest of the first belief is his grouping his beliefs into three groups based on their source, and then each one of them, he'll come up with a reason to doubt.
▶︎ 18:50 And the reason to doubt, these are called skeptical arguments, because there was an ancient Greek philosophical school, the Skeptical School, which was a group of philosophers who thought that we could not gain knowledge, that knowledge was impossible for human beings, and they came up with a bunch of arguments to try to show that. And so he uses some of these traditional skeptical arguments to throw doubt on his groups.
▶︎ 19:14 So first group of beliefs is the most obvious, the most immediate, the most apparent. Right here, right now, how do I know that I'm here? How do I know this shirt is blue? How do I know the sun is shining? How do I know that I'm here? How do you know that I'm here? Well, because the senses. I see the shirt. You hear my voice. I see the sun. And these are called empirical beliefs. Anything that we get through the senses, philosophers call empirical.
▶︎ 19:59 So the first group is the things that we get through the senses, what we see, hear, smell, touch, or taste. And this is a whole lot of beliefs. We get most of our knowledge through the senses in some way. And we trust them quite a bit. So what could be the possible problem?
▶︎ 20:19 Well, he comes up now, once he has this group, the beliefs that we have based on our senses, now he has to come up with a skeptical argument that will render them dubious, that will show how they might be false. Not that they are false, but they might be false, because that's all he needs to knock them out of his foundation, not because he doesn't trust them, not because he doesn't believe them, but because they're not good enough for the foundation. They're not a good starting place.
▶︎ 20:48 So he comes up with a classical skeptical argument, which is called sensory deception. The senses lie to you. Sometimes, you are in a crowd and you hear your voice, your name being called, and it wasn't really your name. Sometimes, you see your friend off in the distance and you wave, and it's someone else and you feel like an idiot. Sometimes, you feel your phone buzzing and you pull it out and it wasn't anything. Our senses trick us. We rely on them, we trust them, and yet they're sometimes wrong. And if they're sometimes wrong, well, then we don't. They're dubious. We can't trust them at all. And therefore, we cannot trust anything we get through the senses, and there we go, we got rid of those.
▶︎ 21:43 But not so fast. Now, this book is written in an unusual style. Like I said, he's not just presenting us with conclusions. He's taking us through the thought pattern. So he has this conversation with himself. It can be very confusing if you don't realize what he's doing. It's a back and forth where he contradicts himself, but it's because he's talking to himself. He's leading himself through these ideas.
▶︎ 22:06 Because he comes back and says, "Well, hold on a second. Hold on a second. Yeah, yeah, yeah, yeah. When someone's far away, I might think that they're not, that someone, that they're not. When I, and a very loud crowd and there's buzzing, I might hear it wrong. But what about this? Here's my hand in front of my face. I'm getting this through the senses. I get it through my sight. I see it, but there's no, it's not far away. There's no fog. There's nothing in between me and my hand. There's no way that this is an optical illusion. Whatever is going on here, it's not the same kind of thing as happens in those situations."
▶︎ 22:50 If I have an empirical belief under good conditions, like it's close by, there's nothing in the way, then it cannot be a kind of sensory illusion like those. And so he has to go back and revise this and say, "Turn out, no, these aren't all empirical beliefs. In fact, those are only the empirical beliefs under bad conditions." And we still have empirical beliefs under good conditions, like when I'm seeing my hand directly in front of my face.
▶︎ 23:29 You see, these survive the first skeptical arguments. The first skeptical argument knocks out empirical beliefs under bad conditions, but it doesn't touch empirical beliefs under good conditions. I can still believe this is my hand, even though I realize my senses trick me sometimes, because they can't trick me about this. That wouldn't be a sensory illusion. So now, can I trust these? Can these go into my foundation? Well, we need a different skeptical argument to make those dubious.
▶︎ 24:00 And he has one. Of course. He wouldn't be going on with this if he didn't have one. The second skeptical argument is a question about dreaming. I'm looking at my hand, and I really, really believe that my hand is here. But what if I'm dreaming? What if I'm in bed and my hand is behind me, and I'm dreaming that I have my hand in front of me?
▶︎ 24:27 I would believe that it's here, and the empirical condition would be simulated perfectly, that there's nothing in between me and my hand, that my hand is directly in front of me, that there's good lighting, that I can see it perfectly, and it would all be false. The belief I have would still be false even though the conditions would seemingly be perfect. And am I dreaming now? Well, I don't think so, but do I know? Am I sure? Are you?
▶︎ 25:02 Descartes thinks, in fact, there's no specific feature that can tell us for sure whether we are dreaming or not. All the things you've heard of, black and white versus color, clarity, whatever, all those can be simulated. All those are things that you've heard. You don't know for sure. They could, those, not knowledge, be part of the dream. And dreams can perfectly simulate empirical data, while still totally false.
▶︎ 25:39 So the dream argument takes care of all empirical beliefs. Any empirical belief you have, anything you get through the senses could be simulated as part of the dream, and then it would be false, even though the conditions are perfect, even though it seems like you're checking to make sure, it would be wrong, and therefore, you cannot put anything through the senses into the foundation. Well, that's a lot. We get a lot of our beliefs through the senses. Is there anything else?
▶︎ 26:15 Descartes thinks there is. And this is going to be one of the big questions throughout this whole course. Descartes thinks that in addition to empirical information, there's an entirely different category of knowledge, which is called a priori. A priori is a technical, philosophical word meaning independent of the senses. We get it without checking our senses. And the things that are a priori are things like logic or math.
▶︎ 26:57 Descartes was one of the greatest mathematicians who ever lived. He took Cartesian coordinates in geometry. Cartesian is just the adjective form of Descartes. He invented those. He invented them, in fact, lying in bed one morning. He hated getting out of bed early. He liked laying in bed until noon. And one morning, he was lying in bed and he was looking at a screen window, and he saw flies walking across it. And he realized, "If you could plot those out, then you could draw shapes and you can come up with geometry for it."
▶︎ 27:33 So, if anyone tells you you can't do anything productive by lying in bed, you tell them about Cartesian coordinates. And if they tell you getting up early can't kill you, you can also tell them about Descartes because he was hired by Queen Catherine of Sweden, who liked getting up early and going out and philosophizing in the cold, and he was dead within six months of being hired by her. So, don't wake up early. Stay in bed. That's the lesson you learn from reading Descartes.
▶︎ 28:03 Now, a priori knowledge would be something like math. So, Descartes says two plus two equals four whether you're dreaming or not. It doesn't matter if you're dreaming. If you're dreaming, you cannot rely on anything you see. But two plus two still equals four no matter whether you're dreaming or not. That's totally irrelevant to the truth of those beliefs. And so those survive the second skeptical argument of the dream argument, which means he needs another argument, another skeptical argument to make those dubious.
▶︎ 28:40 And here, he pulls out the stops and brings out the nuclear bomb of skeptical arguments called the evil demon or evil genius argument. And he says, imagine that an evil demon, very, very powerful demon, has control over you, and his entire purpose is to trick you. Couldn't he have made something in your brain defective so that when you add two and two, you think it's four, your brain goes to four, it's obviously four to you, but it isn't actually four? In fact, it's five or ten or the color blue or something just that you can't compute?
▶︎ 29:28 When the first Pentium chip came out, an early computer chip, it had to be recalled at huge, huge expense because it made this one mathematical error, very, very complex error, and the chip insisted this was right. It insisted this number times this number was this other number, and it was sure, but that was because it had a fault in it. It was badly designed. There was some soldering or something.
▶︎ 30:00 What if our brain is like that? Either God created our brain like that for some reason or evolution did. Evolution doesn't design us for mathematics. It designs us to live long enough that we can pass on our genes, and math isn't terribly helpful for passing on your genes. So it's possible that, even for a priori beliefs, we are being tricked, we are being fooled, we are wrong about those.
▶︎ 30:32 It's basically the matrix. We could be in the matrix and even, but it goes deeper than the matrix. Even our ways of thinking could be flawed. In which case, we can't even know that two and two equals four, so even the a priori beliefs are out.
▶︎ 30:50 And that's where he ends the first meditation. He ends the first meditation with no empirical beliefs that we can trust, and no a priori beliefs that we can trust. He seems to be leaving us... Oops.
▶︎ 31:11 He seems to be leaving us in an epistemological void, a wasteland where we can't trust anything, where we have no beliefs, and we can't put anything into that foundation to begin again. And he says, "Well, if that's the only thing that we can know for sure, then at least we can know for sure, we can know that for sure." And this is where he begins the second meditation, where he's going to try to start building things back up. And he's going to get there with what is almost certainly the most famous sentence of philosophy. You've almost certainly heard it before.
▶︎ 31:59 Because he asks himself, under these conditions, these incredibly, incredibly hostile epistemological conditions, where it's so difficult to know anything, so difficult to rely on any knowledge, any information whatsoever, what can we possibly still say that we know? What could we ever rely on in this situation? Is there a world around us? I don't know. Could be a dream. Could be the matrix. Are there other people? Don't know that. Is there history? I don't know. Is there a God? I don't know. None of this is knowable at this point. With these three skeptical arguments in place, I can't know any of that. I can't even know if I exist. Am I a human? I don't know. Do I have a body? I get that through my senses. So I don't even know if I exist, except...
▶︎ 33:09 Wait a second. I'm doubting if I exist. I'm doubting if God exists. I'm doubting if the world exists. I'm doubting... Who's doing the doubting, then? If I'm doubting that I exist, well, then I've got to be here just to be doing the doubting. I have to exist just to be able to doubt whether I exist or not. You see? This one belief, my existence, and yours if you're thinking along with it, this one belief is unlike all the rest. Because whereas all the others are rendered dubious by methodological doubt, this one is proven by methodological doubt.
▶︎ 34:04 See, he does this conceptual judo flip on the evil demon. So the evil demon is trying to trick him. Great! Okay. He can trick him about the world, trick him about God, trick him about his body, trick... But he's got to be there to be tricked. Descartes has to exist just to be tricked. Is he wrong about his own existence? He's got to exist to be wrong about it. Whatever you come up with, that he's wrong, he's tricked, he's fooled, he has to exist in order to be wrong, in order to doubt, in order to possibly have this be false. And so for that belief to possibly be false, it must be true. He uses methodological doubt against itself. It's brilliant. It's brilliant.
▶︎ 34:52 And this is where the phrase comes from, "Cogito ergo sum." "I think, therefore I am." You see, doubting is thinking something. To doubt is to think something might be wrong. If I doubt that the sun is shining, then I think the sun might not be shining. I think that the belief the sun isn't shining might be false. These are all thoughts. For me to think them, I have to exist. For me to think anything, I have to exist. Thinking requires a thinker. And doubting is a thought. So for me to doubt presupposes a doubter.
▶︎ 35:41 And therefore, not everything can be doubted. Just for the doubting to occur, there must be a doubter. So my existence isn't rendered dubious by doubt. It is proven by doubt. And we have our first belief. We have the first piece in the foundation. It's not much. He doesn't know what he is. He doesn't know what the world is. He doesn't know anything else. But he knows at least that he exists. One thing. One measly, puny little belief, but it's something.
▶︎ 36:24 And now he can start rebuilding. And the next question he asks is, "Okay. I exist. I am. I think, therefore I am. But what am I?" And this brings up a very important philosophical distinction between existence and essence. Existence is that something is. Essence is what it is. So existence is that something is. Essence is what it is.
▶︎ 37:12 Now, he has proven his existence. "I think, therefore I am," but he doesn't know what he is because all of the things he used to believe, that he's a human, that he's got a body, that he's in society, that he's a son, that he's a French guy, all of that is dubious. He can't know any of that stuff now. So he doesn't yet know what to define himself as, and if you don't know what you are, it's pretty hard. Even if you say that you exist, you don't even know what you're saying, really.
▶︎ 37:42 So he's got to determine what he is, his essence, but he only has one tool at his disposal. Methodological doubt. This is the only way he has to determine, to figure out anything. So he's got to use that. He's going to go through all the beliefs that he used to have about himself, what he used to think he was, and he's going to try and adopt them. And when he gets to one that he cannot doubt, that's his essence.
▶︎ 38:13 Now, it doesn't mean that's all he is. Doesn't mean that's the only thing, but it's the indubitable one that he is, the one that he can count on while he is building his foundation. It's the one he can be sure of while he only has methodological doubt as his method, as his way of finding things out.
▶︎ 38:32 So he used to think he was a human being. Nope. All gone. Out gone all that, like he's taught, he was told this. All empirical. Doesn't know any of that. Used to think that he had a body. Nope. We know that through the senses. He was a French guy. Nah, that's way out. Forget that.
▶︎ 38:47 So, what is left? Well, what is the thing that got him his existence, that he was doubting? And what is doubting? Doubting is a kind of thinking. So he knows for sure that he is thinking. Anything else, he doesn't know. I think I'm walking, but that's because I get that through the senses, and I could be dreaming I'm walking. It could be in the matrix that I'm walking, but I'm really lying in a tube without any hair, eyebrows. All that's dubious.
▶︎ 39:23 But I have to be thinking in order to doubt that I'm thinking. So thinking is indubitable because doubting is itself a form of thought. In order for me to doubt that I'm thinking, I have to think. Because to doubt is to think that I might not be thinking, and therefore I'm thinking. So thinking now is the one thing that he knows he is. He might be other things, but for the present, he doesn't know them. Those can't go into his foundation. The only thing that he knows for sure that he is, is he says he is a thinking thing.
▶︎ 40:11 He says there's a whole lot of other stuff in the universe that might not be. He thinks, ultimately, he comes up with an idea called Cartesian dualism. And this is the idea that everything in the universe can be divided into one of two categories. That's why it's a dualism. It's Cartesian because he came up with it.
▶︎ 40:39 Everything in the universe, you can divide, you can classify into one of two classes. Thinking things and material things, and that's it. Minds and bodies. That's all there is. And we are minds. We have some weird connection to a body.
▶︎ 40:58 This was a big problem. The mind-body dualism is a big problem. How are they connected? But minds are defined as thinking, and bodies are defined what he calls extension. Means they take up space.
▶︎ 41:17 Now, he's got one last idea, one last belief that survives methodological doubt. We have his existence. He exists, that he is. We have his essence, thinking. He's a thinking thing, what he is. And he's got one more, and it has the same structure as the other two, which is that it's proven by methodological doubt. It's proven by methodological doubt. Instead of being disproven or shown dubious, it's actually made certain by methodological doubt. And this is that he has ideas.
▶︎ 41:51 I have the idea, the perception of the sun coming in. Now, I don't know if it's true. I don't know if there actually is a sun there. But in order for me to be fooled into thinking there's a sun there, into believing it is, into having an illusion, I have to have the perception of a sun. The people in the matrix, they perceived a world around them. The world wasn't real. There was nothing corresponding to those ideas outside signals in their brain, but they had those perceptions.
▶︎ 42:29 They had to in order to be tricked. In order to believe those perceptions were real, they had to have the perceptions. So I have this sensory array. I just don't know what's causing it. Could be an evil demon. It could be a dream. It could be the matrix. But I still have to have it just to think, just to be wrong about it being real. And he calls these ideas.
▶︎ 43:00 So I exist, I think, and I think ideas. And that's his foundation. Three things. He doesn't know if the world exists. He doesn't know if God exists. He doesn't know if other people exist. He doesn't know if he's ever been taken a step. He doesn't know anything else. Doesn't know anything about the world beyond him. But he knows he exists. He knows he thinks, and he knows he thinks ideas. And from that tiny, tiny, puny beginning, he's going to rebuild his knowledge base, he's going to bring back the world, he's going to prove that God exists, and he's going to create science.