▶︎ 0:01 Descartes now has his foundation. He has spent the first meditation emptying his thought out, using his methodological doubt to render anything that was dubious and take it away, and he's found three bulletproof, doubt-proof beliefs. He now has his existence, he does exist, he has his essence, that he's a thinking thing, and he has the fact that he has ideas even though every single one of them might be wrong. Very, very little to go on, but it's from here that he's going to reinstate the world, bring God back, and create science.
▶︎ 0:38 Now, his only method at this point is methodological doubt, and it's a very crude method. It gets rid of so much. He needs to refine his tool at this point in order to build things back up. So he moves from methodological doubt into a new epistemological tool, because he looks at the beliefs that he has established, these three that he has found to be doubt-proof, and he realizes there's something in common with them. He looks at them and he sees, what is it about them that has enabled them to withstand the doubt? And what he decides is that, for all three of them, he's able to have what he calls a clear and distinct perception of them.
▶︎ 1:30 This is his phrase, and it's become a technical term. It's because he can have a clear and distinct perception of these that he can be sure that they're true, that they can withstand the doubt that he's using to filter out so many of his beliefs. And remember, the ones that he's filtering out, he's not saying they're wrong, he's not saying they're false, he's not saying there's anything wrong with them, and these scenarios that he came up with, like he might be dreaming, there might be an evil demon, he doesn't believe those. He doesn't think, he's not worried about how the beliefs might be false.
▶︎ 2:06 This is something that will expose certain features about beliefs. It's a tool to sort them into strengths, into types, and he's already sorted them into empirical and a priori types. And we're going to see, he's going to drive a lot more out of those. But he has a clear and distinct perception of these three, and what that means is that he's able to see everything there is to know about them.
▶︎ 2:38 He's able to take them apart, so to speak, and look at every single part of them and then put them back together, and he knows that he's seen all there is to it. He's drunk it down to the bottom. There's no corner that he hasn't looked around. There's no place of shadow where there's possibility that that mistake could be, that error could be. He's shone a light over everything and he's seen all aspects of it and he knows that it must be true.
▶︎ 3:10 And once he has done that, he feels he can trust it. And this has been called the truth rule. The truth rule is that if you can have a clear and distinct perception of something, then it must be true.
▶︎ 3:33 So very briefly, we're gonna have one together now, just so I'll show you what it feels like, because this phrase is very unclear and indistinct. Math, of course, is a very good example of a clear and distinct perception, and we can just take a very simple topic. So the question is can we know that two and two equals four? We believe it, but can we really, really know it? Can we be absolutely sure that it's true?
▶︎ 4:07 How do you know that it's true? Just because Mrs. Johnson told you in first grade? Well, that's not good evidence. She said some things that are probably a little dubious. Because you've taken two things and two things and put them together? Well, that's not perfect evidence. As we're gonna see when we return to Hume. But for Descartes, the evidence of this is a priori. It's that we look at the idea, we take it apart, and we see its truth.
▶︎ 4:40 So we look at the ideas here. What is two? And all that two is, is just a duality of entities. There's nothing else to the idea of two than that. So we take apart these ideas and we see that this is the only thing that two means, and we look at addition, and all addition means is bringing them together. There's nothing else here. There's no underside, there's no corners, there's no backside. That's it.
▶︎ 5:12 So two plus two is just this. This is it when we take it apart, and we're not looking at just the words or the symbols, but the actual meaning. All it is is two dots and two dots brought together. And the only meaning that four is, is four dots. And the equals is what's here is the same as what's there, which they are. So if you focus entirely on this, it's very, very, very simple.
▶︎ 5:49 We only have this with small ideas, because you have to absorb everything about the idea at once and have it entirely in your head, every piece of it, all at the same time. And if you go through this and you really focus on it and you really see all there is here, then you can know for the first time that two and two really does equal four. You believed it before, I hope, but now you know it in a totally different way. Now, Descartes would say, you know it for yourself. You have proved it for yourself.
▶︎ 6:26 Instead of taking it on faith, taking it on reliance of, on authority, you've seen the truth of it. The truth of it is shown forward, and there's no way you can doubt it at this point. There's nothing else to it. So we now have had a clear and distinct perception of this very, very small, minor, mathematical idea, and we know it's true because there's no way it could be false.
▶︎ 6:53 There's no other meaning that there could be, where there could be a surprise. There could be something that later, "Oh, I didn't think of that." No, there's nothing else to think of. There's no way we could later remember some relevant factor that we're not entertaining now. We're entertaining every single factor that's possibly relevant. We've got it all and we see the truth of it. And this is what a clear and distinct perception is. This is the highest level of epistemological evidence possible for Descartes.
▶︎ 7:25 And it can only be had a priori. You cannot have a clear and distinct perception of anything empirical. For one thing, as he says, you can only ever see one side of something. So I, while I'm looking at the front of this, I cannot see the back of it. And therefore, I can nev... And if I look in the back, now the front is blocked.
▶︎ 7:47 So this is a topic that a much later philosopher, 20th century German philosopher, Husserl, talked about a great deal. And so there's no way to use sensory data to take in all aspects of something at once. Every sensory perception is partial, by definition, by its nature. It's always from one perspective and it's always partial.
▶︎ 8:12 But an idea, if it's simple enough, if you can familiarize yourself with it, if you can turn on all different angles and get it all at once in your head, you can absorb it and have the entirety simultaneously and know that every bit of it is right. And this is how we're going to move forward. We're going to move forward through these clear and distinct perceptions. This is what we can trust, he believes. We've got our foundation with those three ideas, and now we have a tool, not just that will tear down, like the methodological doubt, but that can build with clear and distinct perceptions.
▶︎ 8:57 And what we need to do now is we need to kill the evil demon. The evil demon was the third skeptical argument, the really, really powerful one, the one that threw everything in and out, all empirical beliefs and all a priori beliefs. We've taken back some a priori beliefs, the simple ones that we can have a clear and distinct perception of. We've got those back, but there are very few of those. And you can only have one at a time.
▶︎ 9:27 So we need to start beating back these skeptical arguments from the first meditation. We need to get rid of the evil demon. We need to get out of the matrix. And the only way that we can do that is by proving that there is a God for Descartes. Only a God can take down this evil demon. Only if we know that there is a God can we trust our senses enough to know that there's a world outside of us.
▶︎ 10:00 Until we do that, we can't trust any of those ideas. We have the three beliefs: our existence, our essence, and our ideas. We cannot trust any of those ideas. They all could be dreams, they all could be matrix, they all could be simulation. We need to have God to bridge what's inside our skulls and what's outside. We need God to be able to look at the ideas in our head and look at the world outside of us and say, "Yes, these match."
▶︎ 10:35 The things you see are caused by the things that they look at. When you look at a chair, then there is something there that is causing you to have the idea. That's what we need in order to do science. Remember, that's the whole goal that we're aiming at. We want to be able to control the world, be able to have medicine, to be having machines, and we need to have an external world to have that.
▶︎ 11:03 So our next step is to defeat the third and most powerful skeptical argument from the first meditation, the evil demon. And to do that, Descartes is gonna prove that God exists, which I will do right now. Nothing up my sleeves. I have no props. I will prove that God exists right now. This is a very common hobby for philosophers. For a long, long time, this is something that philosophers like doing.
▶︎ 11:39 This proof, The Meditations, this book actually has two proofs. One of them is terrible. It uses a lot of medieval ideas you have to buy into to get it going, and we're not gonna touch that one. The other one is one that Descartes basically plagiarized. It's known as the ontological proof. It was created by a 12th century, I believe, monk named St. Anselm. I used to drive by a church of St. Anselm Church. I always wondered if they chanted this proof. I kind of doubt it, but I imagine them doing it.
▶︎ 12:25 And it is entirely a priori. There are some empirical proofs, but Descartes can't have that because he cannot know there's a world outside of him yet. He needs God to prove that. So we can't use that to prove God. The only resources he has at this point are the three things he has in his foundation. That's it. That's it. His existence, his essence as a thinking thing, and his ideas, every one of which could be wrong. From those, he's gonna build a god. And not only from those, but actually only from one. Only from his ideas.
▶︎ 13:15 The proof begins from the fact that Descartes has ideas in his head. I have an idea that I'm seeing a wall. I don't know if there really is a wall. I don't know if walls exist. I don't know if the world exists, but I know that I have an idea of a wall.
▶︎ 13:37 Now, the first thing that Descartes points out is that ideas have essences. We don't know if the thing that they're about has existence. I don't know if walls exist. But I do know that there's a thing that is a wall. So when we look at these ideas, we do not know if they are true in the sense that anything outside of my head corresponds to them. We do not know if anything outside of me is causing them. Could be a dream, it could be the matrix, it could be a demon. But we do know that even if they don't have existence, they do have essence.
▶︎ 14:35 Unicorns don't exist. I hope that doesn't shock anyone. I hope I didn't burst any bubbles there. But they do have an essence. The essence of a unicorn is a horse with a horn. If the idea of a unicorn did not have an essence, then I could not even deny their existence, because what would it be that I'm denying the existence of? If I didn't know what I was talking about when I was talking about unicorns, and you didn't know what I was talking about, then saying they don't exist would be meaningless.
▶︎ 15:05 If I said, "Flabbleblahs don't exist," that doesn't mean anything because it doesn't have an essence. You don't know what I'm talking about. But because you know what unicorns are, horses with horns, you know what I mean when I say they don't exist. I can only deny existence of them because they have essence. There is a meaning, a definition. There are necessary properties to this idea, even though they're only an idea. There's nothing beyond an idea to them. It still has an essence to them, and
▶︎ 15:40 It's an essence that I can't control. I can't change the meaning of unicorns. That's just what they mean. Whether they exist or not, they're in my head. And these essences can have implications. They can entail other properties. Because it has one property, that could mean it has other ones, too.
▶︎ 16:09 So his favorite examples are always geometrical. He has the idea of a triangle. The idea of a triangle is very easily a shape with three sides. That's the definition of a triangle. He doesn't know if there are any triangles in the world. All he knows he has the idea of it, and yet that idea has necessary properties. It has an essence. It has to have three sides, or it's not a triangle.
▶︎ 16:45 If I say, "I just saw the rarest thing, I saw a four-sided triangle," you would say, "No, you didn't. That's not a triangle." I can't see one because it has to be three sides to be a triangle. But it's not just three sides. Once you have that essence, there are further properties you can derive from that if you know much about geometry, like I don't, but like Descartes did. Any shape with three sides, connected, the internal angles must add up to 180 degrees. That's a law of geometry.
▶︎ 17:21 Again, it doesn't matter if there is no triangle in the universe. It doesn't matter if there never has been a triangle. If there never will be a triangle out there, the idea has necessary properties to it. Whether there's anything like that correspond to it is irrelevant. The idea of a triangle has an essence, it has three sides, and that essence has necessary properties, like the internal angles adding up to 180 degrees.
▶︎ 17:53 Purely a priori, purely about the idea, we are still restricted. You can't choose to have a triangle whose internal angles add up to 179 degrees, 'cause then it wouldn't be a triangle. It must have this property.
▶︎ 18:10 Third step. Among my ideas is an idea of God. What is the essence of that idea? The essence of the idea of God, according to this proof, is to be a supremely perfect being. A supremely perfect being isn't just perfect in one way or another way, but is a being that is perfect in all ways. It's completely perfect. It's absolutely perfect. It has all possible perfections.
▶︎ 18:46 Now, that essence, just like the essence of three sides, has implications. That entails other properties. The three sides entails the 180 degrees; the definition of all possible perfections means that any perfection it could come up with, God must have it. So in order to flesh out the definition of what God is, all you have to do is come up with possible perfections. If you come up with a possible perfection, God has it because the idea of God is to have all possible perfections. If you're thinking of a God that does not have a possible perfection, you're not thinking of a God any more than a four-sided triangle is a triangle.
▶︎ 19:35 So what are some possible perfections? Well, omniscience, knowing everything. Perfect knowledge. Yep, okay. Perfect knowledge is a perfection. God is the being with all possible perfections, therefore God is omniscient. Omnipotence, perfect power. God is the being with all possible perfections. Perfect power is a perfection. God is omnipotent. Omnibenevolence, perfect goodness. Possible perfection, God has it. Perfect existence. Existing from all time, for all time, self-caused. That's a possible perfection. God has all possible perfections. God has perfect existence. Therefore, God exists.
▶︎ 20:30 The idea of God is the being that has all possible perfections. Existence, existence is a perfection, therefore God has it. If you are thinking of a non-existent God, if you are an atheist, then you are not thinking of God. You are like the geometrician thinking of a four-sided triangle; that's not a triangle. You cannot deny the existence of God, according to this proof, because whatever you're denying isn't God.
▶︎ 21:17 If you deny existence of that being, that's no longer God because it lacks a perfection. You are saying the being that has all possible perfections does not have a possible perfection. That's a contradiction. The only way that you can be consistent, that you can be even talking about the idea, is if you attribute existence to it. Therefore, you cannot logically deny that God exists.
▶︎ 21:48 This proof has never convinced anyone in history. No one has ever become religious because of this proof. But the question is, if you think it's wrong, which most people do, where is it wrong? Where is the mistake?
▶︎ 22:14 Philosophy's wonderful because you can argue against anything. There are no authorities. Doesn't matter. Plato said it doesn't matter. You can say they're wrong. But you have to have a reason. You cannot just say, "It's wrong. Obviously it's wrong. Can't be right." That's not a legitimate reason to reject a belief. You can't just say, "It must be wrong. I don't believe the conclusion." You have to see why it's wrong.
▶︎ 22:52 Descartes is not saying, "God exists because I believe in God." Descartes is not saying, "I have faith." Descartes is not saying, "The Bible says, God exists, therefore God must exist." Descartes is giving us reasons. He's laying out the tool that all philosophers use, which is an argument. He's putting together premises, ideas that lead to a conclusion.
▶︎ 23:18 Now, you can attack the premises, you can reject a premise, you can say it doesn't lead to the conclusion, but you cannot just say, "I don't like the conclusion, therefore I reject it." You've gotta find a flaw in it. You are welcome, you are encouraged to look for a flaw. Please. But you have to find one, you can't just reject it. You have to be open to being wrong. You have to be open to changing your mind. I am not trying to convince you of anything, mind you, except that we should all be reasoning. So let's look at some possible objections.
▶︎ 24:06 One objection is, "Hold on a second, hold on a second, all you're doing is thinking. You can't think something into existence. You can't just put a bunch of words and ideas together and poof, something exists because of that." That's true. And that's not the reason, the reasoning of the argument. The argument doesn't cause God to come into existence. The argument simply recognizes that God has this property.
▶︎ 24:35 The fact that we perceive that triangles have 180 degrees of internal angles doesn't make it true. If it did, then we could change it. We could all get together and decide, "Let's have 179-degree triangles." But we can't. We have no control over it because we are not making that happen. We are recognizing that it has this property. We are recognizing that it is. We are seeing it, not making it. So when we go through this argument, the argument doesn't create. The argument recognizes. The argument perceives. It is God's property that it is showing us rather than giving.
▶︎ 25:21 What about the idea of God? This hinges on the idea of God as a supremely perfect being. That's not the idea that everyone has of God. People have other ideas of God. Let's take this idea, the idea of a supremely perfect being. Let's forget about God for a minute. Let's just call it Bob. Bob is a supremely perfect being. Bob has all possible perfections. Bob is omniscient, Bob is omnipotent, Bob is omnibenevolent, and Bob has perfect existence. By definition, by the argument, Bob, as this idea, must have those properties. Therefore, Bob must exist. And Bob seems an awful lot like God, so we can worship Bob.
▶︎ 26:08 Even if that's not your idea of God, this being with all possible perfections must exist, according to the argument, and that's all that it needs. You don't have this idea of God. You do now. You shouldn't have listened. Sorry. You've been infected with it, and now you have the idea. Once you have this idea, you can no longer deny God's existence, according to the argument. According to the argument, with you have this idea, you can no longer consistently maintain atheism. To deny that God exists is to commit a contradiction.
▶︎ 26:45 So sorry, should have had a warning on the label of the video, "Do not watch this if you want to maintain consistent atheism." But now that you have the idea, according to the argument, you cannot deny that God exists without committing a contradiction. Please come up with other objections. That's what we do. That's how philosophy works. Anyone can come up with one. It just has to be good. It just has to be relevant. It has to be reasoned. It can't simply be a reaction, "I don't like this. I don't want this."
▶︎ 27:24 I refuse it." Now, if we think back, why did Descartes do this in the first place? Why'd he bring this up? Why did he talk about God at all? It was in order to slay the evil demon, to get rid of the third skeptical argument. The way that that works is through one of those perfections. God exists, that's one of the perfections. Another one is omnibenevolence. God is all good. Well, an all-good being would not deceive us. An all-good being would not directly deceive us, but nor would this being allow us to be deceived in a way that we could not have some resources to resist.
▶︎ 28:22 You see, even if God doesn't directly deceive us, Descartes is arguing, if God leaves us in a position where we cannot avoid deception, then God is responsible for it. If you take someone out into the middle of the desert and you kick them out of the car without any water and you drive off, even if you didn't actively murder them, you put them in a position where they cannot live. And so you're responsible for their death. If we are in the clutches of the evil demon and there's no way for us to find truth, there's no way for us to resist this deception, then God is allowing us to be deceived and God would be responsible for it. But His benevolence won't allow that.
▶︎ 29:05 So God must have put something in our hands that would enable us to find truth even if we're under deception, even in the worst epistemological conditions. And what is our best tool for finding truth? What is the best epistemological condition that we can achieve? Clear and distinct perceptions. If those are wrong, if that is the best we can have, and those are wrong, those could be wrong, then God would be responsible for our deception. And therefore, Descartes is arguing, we can absolutely rely on clear and distinct perceptions.
▶︎ 30:01 When we have gone through that process and we have seen it and we've examined every angle and every shadow and every underside and every backside of an idea, and we are convinced that it is true in a way that we cannot do any better, it must be true. Because we know that God exists and God is not deceptive. We must have some way to get knowledge, and that's the best way we have. So the third skeptical argument cannot be true.
▶︎ 30:33 We cannot be completely at the mercy of a being that can trick us in a way that there's no way for us to overcome. We have a way to overcome it, but it's incumbent upon us to use it. The freedom to use or misuse our mind is up to us. We're the ones who will decide whether we rely on clear and distinct perceptions and work at them and look at ideas very care... Because it's a lot of work, as you saw.
▶︎ 31:07 Two and two, if it's four, it's pretty easy when it still took us a few minutes to go through it, really focus and concentrate on it. It's not easy. But if we get lazy and relax and don't go that route, it's our fault, not God's fault. It's our fault if we make errors. At that point, we now take on responsibility for any errors we make, because we have the ability to avoid errors if we put in the effort, the effort that Descartes calls science.
▶︎ 31:45 Because if we look back at those three groups of beliefs from the first meditation, what we saw was the first two are types of empirical beliefs and the third was a priori. The first two fell to sensory deception and dream arguments, as the skeptical arguments, and the third fell to evil demon, as the skeptical argument. Well, the evil demon has been refuted. The evil demon, a stake has been driven through the heart of the evil demon. And now we can have a priori beliefs if we work at them, if we make sure they're right, if we put in the effort.
▶︎ 32:26 What about the others? What about empirical beliefs? Well, again, Descartes says, if all of our empirical beliefs are wrong, if all of our perceptions of the world are caused by something that has nothing to do with what they look like, if it's all a dream, if it's all the matrix and none of this stuff exists, well, we wouldn't be able to find that out, and God would be responsible for our deception. So there must be a world out there that is roughly like what we see. But it doesn't have to be exactly like it.
▶︎ 33:12 The senses, Descartes argues, are very poor tools for gaining knowledge. They still are subject to deception. They are crude. They are subjective. If we're in the same room, I can feel like it's pretty hot and you can feel like it's pretty cold. That's not a good basis for science. We can't do an experiment of, "How do you feel in this room?" Because that's not replicable. I'll find one response and you'll find another.
▶︎ 33:46 Sensory data is not good data for the sciences, Descartes believes. It's too subjective. It's too variable. People will find different answers. We don't get the same answers from it. And it's too vague. What would I say the room is like? It's kinda warm. That's not a good measurement to do an experiment with.
▶︎ 34:15 What would be a good measurement? 78.3 degrees. That's a good measurement. That's something that you can reproduce on the other side of the world, that you can reproduce 20 years from now. That's exact. That's not subjective. That's perfectly objective. You and I can disagree about how pleasant it is, how comfortable it is, how warm or cool it is, but we'll both agree it's 78.3 degrees. Because measuring changes the subjective into the objective.
▶︎ 34:56 Measuring quantifies what is otherwise vague. It makes it exact, it makes it precise, it makes it replicable, it makes it universal. It is this, the number is the same for everyone. What we do when we do science, what we need to do to put science on the right track, Descartes is saying in this book, in 1641, is we need to take whatever empirical observations we make and we need to transform them into numbers.
▶︎ 35:39 That's what Cartesian coordinates are. Cartesian coordinates are taking a shape and turning it into numbers. Shape is vague, shape is rough. Numbers are perfect. Numbers are exact. Numbers are precise. Once we have numbers, we can record it, then we can communicate it, then we can replicate it. And that changes the experience from the first two groups, the empirical, to the third group, the a priori.
▶︎ 36:18 What we're doing is we're taking all of this vague sensory data and we're absorbing it into our mind. We're turning it into mental structure. We're turning it into something that the mind can then use, can control, can understand, and it's done through something that's so simple, taking measurements. Taking measurements quantifies the qualitative. It transforms Groups 1 and 2 into Group 3, and Group 3 survived skeptical arguments that Group 1 and 2 fell to. Group 3 a priori beliefs are certain. Group 3 a priori beliefs are exact.
▶︎ 37:20 And what Descartes is saying here, Descartes is saying, "Of course, we need to use our senses. The senses are the only way that we get to know the world outside of us. But we have to correct for them." See, the senses are still deceptive. If I look at a star, the star is exactly as bright as a candle. My senses, if my eyeball could talk to me, my eyeballs say, "Oh, yeah, those are the same. Same amount of heat, same amount of light. Yep, star and a candle. Yep." But I'm not gonna believe that. My brain has to correct for that. My reasoning overrules my senses.
▶︎ 38:09 If I look at this section of air, my eyes say it's empty, but my brain knows it's got all kinds of horrible little germs and chemicals and things in it, and radio waves that I can't perceive. The senses are necessary, but they're not very reliable, according to Descartes. We have to use our reason to correct for them, and the number one best way to do this for science is by transforming all of the subjective, all the qualitative, all the relative into exact numbers.
▶︎ 38:53 And this is the moment when everything changes. This moment right here. This is the moment when all of Western civilization gets put onto a different track. Up until then, knowledge of love was the same as knowledge of numbers. These were just different types of knowledge. They were equal. It's irrelevant.
▶︎ 39:19 But now, at this moment, Descartes rules, a couple of others, Galileo, a few others, but they're all very few people, that the only thing that science should deal with is what can be quantified. If it cannot be put into numbers, it cannot be the subject of science. Science, it's something else. It's not that it's not real, it's not that it's not good, but it's not what science should be focusing on. The only thing that can be a subject of scientific endeavor, knowledge, conclusion is what can be measured, what can be quantified. And with that little rule, science, modern science was born.
▶︎ 40:13 With that little change, now you can see me through a computer. That's just ones and zeros. That's all a computer is. That's all this code is, is numbers. The only reason you can see me is because we've reduced all the visual, all the color, all the wonderful timbre of my voice into numbers. We have doubled our lifespan, we have cured diseases, we have walked on the moon, because of math.
▶︎ 40:49 Galileo said, "The book of nature is written in the language of math." That was the one change that was not foreordained. It was not obvious. That was the one change that changed everything. That's the reason why you and I have the computers, the TVs, the airplanes that can travel around the world, because of this moment, because of this weird little thought experiment this French guy did on a snowy evening in 1619, and that we have now done together.