▶︎ 0:00 So far, we've looked at Descartes' skeptical questions where he tried to establish a new form of science. Then we looked at Hume's skeptical questions where he tried to reform the way that we understand science. And these two are representatives of the two big schools in early modern philosophy: rationalism and empiricism.
▶︎ 0:26 These two groups of thinkers had extremely different views on the nature of knowledge as well as the extent and the limitations of it. And as the period went on, the two centuries or so went on, they diverged further and further apart from each other until it seemed that there was no talking to each other, or they were incompatible, fundamentally incompatible.
▶︎ 0:53 Until Kant. Kant came at the end of the 18th century, and he brought the period of early modern philosophy to an end. He is universally, pretty universally considered one of the great philosophers in the history of philosophy. I think he and Aristotle are probably the two greatest. He touched on every branch of philosophy, and every one of them, he revolutionized fundamentally.
▶︎ 1:26 He's most famous for his first big book, and I do mean big, 800-page tome of a book, the Critique of Pure Reason, which he published in 1781. But it wasn't read a great deal. It was misunderstood. And part of that was because of the style. He's a terrible writer. His writing has been described as dry, obscure, opposed to all ordinary notions, and moreover, long-winded. And that description of that was by an author named Immanuel Kant. That was his description of the first Critique himself.
▶︎ 2:10 So he wrote this book, this Prolegomena to Any Future Metaphysics, as a sort of a shorter, easier version of his philosophy. Easier, it's still not easy. But it's certainly much, much, much shorter. And it gets the basic ideas. The first Critique is enormous with so many details and so many nooks and crannies and back alleys, whereas the Prolegomena really gets to the main point of it. And that's what we're gonna be going for in this lecture.
▶︎ 2:41 We're not going to be chasing down all the details because there are just so many of them. We're trying to see the world that Kant saw. We're trying to get the insight that drove his philosophy rather than all the minutiae of it.
▶︎ 3:02 And like with Hume, there's one big argument here. There's one big idea. And again, if you get that, you've got the book. He takes this idea. The first part is the preparation for it, leading up to it. Then there's the big idea, and then he applies it in three different ways.
▶︎ 3:24 So if you get that big idea, you're golden. But again, as with Hume, it's a difficult, complicated, counterintuitive idea, though it has been enormously influential.
▶︎ 3:42 He was, Kant was, trained as a rationalist. He was trained as a person who relied on a priori reason to understand the structure of reality, to pursue metaphysics. And he was committed to that program until he read David Hume. And he says this was the cataclysmic event for him. He thinks this is one of the signal events in the history of philosophy, and certainly one of the events, one of the great events in his life, that he said in his famous phrase in the introduction, to this book, woke him from his dogmatic slumbers.
▶︎ 4:25 By dogmatic, what he means is that he had been trusting his reason to be able to accomplish these feats. He had been assuming that he could simply sit in a chair the way Descartes did in that snowy cabin in November of 1619 and turn inwards and reflect and think about ideas, and through that process of merely reflecting on the logic and the internal logic of ideas, come to understand facts about reality. That the way the inside of the mind works is parallel to the way the outside world works. And therefore, by studying this, you can learn about that. That's the way that a priori metaphysics works. It's a priori, meaning you're not using your senses to look around because you assume what you find out on the inside reflects what's happening on the outside.
▶︎ 5:26 And the key word there is assume. The reason why Kant came to believe that this project is dogmatic is precisely because metaphysicians were assuming that was the case. They were assuming that the logic of the mind works the exact same way as the metaphysical reality of the world. And therefore, by studying the one, you learn about the other. But no one was proving it. No one was establishing it because it's extraordinarily difficult.
▶︎ 6:02 How can you possibly do that? And it was Hume who shocked him into asking this question: How do I know that the way my ideas fit together is the same way that events and objects fit together? How do I know that? I have to believe that in order for a priori metaphysics to make sense. Otherwise, a priori thinking tells me nothing about the world, and that's exactly what Hume said.
▶︎ 6:34 Hume said that a priori thinking only gives us what he called relations of ideas, which are just the way ideas relate to each other, that tells us nothing about the world outside of us. We can always be the turkey who doesn't know that Thanksgiving's coming. The turkey assumes that its trust of the farmer is fully justified, but it doesn't know that there's something else going on in reality that it has no awareness of. And for Hume, for all we know, that's us. And therefore, for Hume, we cannot simply go on a priori thinking and trust that it will tell us about the world.
▶︎ 7:19 For Hume the fundamental, the most important relation is causality, cause and effect. It is connecting certain events as causes, with other events as effects. And his claim was we cannot do this a priori. We cannot know what will cause what merely by thinking. There is no way that internal a priori logic can tell us what will make what happen in the actual world.
▶︎ 7:51 As far as our ideas go, we can imagine anything causing anything. We can imagine snapping your fingers and the sun going out, and that's as logical as the billiard ball hitting the second one, the second one moves. The only reason we know that the latter is real and the first one isn't is because we've seen the latter happen over and over and over again. And we know snapping the fingers, and that's not a good example, but the sun doesn't go out.
▶︎ 8:24 And even then, of course, Kant says that even then the connection we forge between the cause and effect, between the two events of the first billiard ball hitting the second one and the second one moving, is not done by reason. It's done by an instinct, a reflex, what are called custom or habit, that has no rational basis whatsoever. It is just our monkey brain that is leading us to react in a certain way to certain stimulus. Kant thought this was brilliant, and this shook the entire way that he thought.
▶︎ 9:09 But Kant said that question that Hume raised didn't go far enough. Hume talked about one connection, the connection causes and effect. What about all the other connections we make? For Kant, the fundamental nature of knowledge is making connections, that when you know something, what you're doing is you're making a judgment, and a judgment is the connection basically of a subject and a predicate. So for Hume's issue, causality, what you're doing is you're connecting a cause and effect. You're connecting the person's foot and the footprint. You're connecting the ball hitting the second ball and the second ball moving. This is forging a connection between events.
▶︎ 9:59 But to know anything is to connect some kind of predicate, some kind of quality to a subject, to some kind of thing. So if I say, "My dog Ned is brown," then we take the subject, Ned, my dog, and we take the predicate, brownness, and we connect them. Ned now has the quality or property or something called accident of brownness, and that's now a piece of knowledge. Now you know something you didn't before, and the knowledge has the form of the forging this kind of connection. Taking a property, taking a subject, and putting them together.
▶︎ 10:43 And Kant says, how do we do any of these connections? Not just causality, how do we make any of the connections that form the entirety of knowledge? Let's take Hume's question and generalize it as much as possible. Because this math and science, these are just a whole bunch of connections, a whole bunch of connecting predicates and subjects. So how do these take place at all?
▶︎ 11:17 And some of these, some connections that are made are physical, and some connections that are made are metaphysical. We saw Descartes take God as a subject, and then take a whole bunch of predicates, omniscience, omnipotence, omnibenevolence, and existence, and Descartes combined those. God has omniscience. God has omnipotence. God has omnibenevolence. God has existence. And that's how he proved the existence of God. He was making these claims to knowledge that, again, had the same structure.
▶︎ 11:57 But the key point, the thing that made this metaphysical for Kant, and for Hume, is that it transcended all possible experience. Descartes did not, if I see my dog Ned, then I see in the world the subject Ned and the predicate existence combined there, right there. I see brownness combined with my dog, I see existence combined. So there is the fact with the subject and predicate together right there, and I perceive their togetherness. That's how I perceive the fact.
▶︎ 12:40 But I do not perceive the existing God. I do not perceive the omnipotent, omnibenevolent, omniscient God. I do not perceive the existing God. And therefore, the connection that Descartes made was a priori and, and now the question is, how could he know that? The basis that he used was simply the ideas in his head. Well, the idea of God is the being with all possible perfections. The idea of existence is to be a perfection, therefore, these ideas have this relationship.
▶︎ 13:18 But that makes the dogmatic assumption, that the way my ideas in my head relate to each other must reflect the way things outside of my head operate. That if my ideas fit together like this, then actual reality fits together like this, and that is the fundamental dogmatic assumption that Hume woke Kant from. Hume demanded that we prove that. And Hume thought you can't. You can't prove it.
▶︎ 13:57 You can find relations of ideas, but that only tells you about the ideas. You can perceive matters of fact and then you know those matters of fact are real, but only if you perceive them, and that's it. That's the entirety of knowledge. Relations of ideas, and perceived matters of fact. Nothing else.
▶︎ 14:21 Kant thinks that Hume's question is the right question. How can we know that our knowledge in our heads reflects the way the world is? But his answer was wrong. We can't. Hume gave up too much. Hume's answer leaves us in too difficult a state. The state that Hume was happy to leave us in of just, well, we have to react this way because this is the way our brains are built, was not good enough for Kant.
▶︎ 15:02 Kant was the figure of the Enlightenment, and for Kant, we have to have a reason to believe this or we do not have the right to believe it. If you don't have a rational justification for your belief, then you don't have the right, the epistemological right to believe it. That is what it is to be a rational being, to only believe what you can argue for, what you can justify, and therefore, the state of simply reacting to the perception of constant conjunction of events, first the billiard ball hits, the second one moves over and over again, the fact that we just react the way our leg moves when it gets hit by the hammer of the doctor, that's being an animal, which is exactly what Hume said.
▶︎ 15:58 Hume said, "Yep, that's what we are. That's all we are. We're animals." Kant says, "No. Amidst all our philosophy, we must be humans, not an animal. We must have reasons for our beliefs."
▶︎ 16:13 So Kant takes up Hume's challenge. Kant takes up Hume's question. But in order to answer it, he feels that Hume surrendered. Hume just gave in. Kant wants an actual solution to it so that we have a rational justification to believe that our ideas, our thoughts do work in sync with the world around us. So that he will not be dogmatic anymore like the rationalists. He will have an argument. But nor will he give up this ability to have knowledge of the world.
▶︎ 17:01 To understand what is being given up, we have to move into preparation for the argument. And it's a bit technical, it's a bit tedious, but we have to get this out in order to understand the way that Kant phrases the question. In the preparation for the big argument, Kant is looking at our judgments. All of knowledge is judgments. All of judgments are connections, and he wants to understand the different types. In order to understand the nature of knowledge, we have to understand the different kinds of connections that are possible.
▶︎ 17:36 And he lays out two different, two pairs of contrasting terms. One is one that we're quite familiar with, which is a priori and empirical. It's Kant, so he can't just say empirical. He's got to use a fancy word. The word he uses is a posteriori, and you can see that's posterior, after, after we've consulted our senses, as opposed to prior, before we've consulted our senses. It's not really a chronological connection, but that's the analogy that's used.
▶︎ 18:17 So all that a posteriori is is a synonym for empirical. It's another way to say empirical, just Kant has to be annoying and have big words instead of simple ones. We're going to be using empirical, but he often used a posteriori, just to let you know. This is one contrast, and we're quite familiar with this from Descartes and from Hume. But Kant adds a new contrasting pair.
▶︎ 18:44 Kant adds synthetic and analytic. And this one we haven't seen before. We've seen something pretty similar to it, but we haven't seen this one before. So to explain this one, I want to ask two questions. The first question is how many bachelors are there in New York City? Now, how would you go about answering that? You can't do that a priori. You can't just think about the nature of bachelors of New York City, you can't think about the meaning of these terms. The only way you could answer this is empirically. You would have to go and pass out a survey and do sociological studies and look at marriage records to find out how many bachelors or unmarried men exist. There's no logic, there's no inference, there's no way to reason it out.
▶︎ 19:50 The second question is how many married bachelors are there in New York City? Now, that sounds like the same kind of question, how many are there, but it's a completely different question, completely different kind of question. Because that one you can answer right now. None. There's zero. Because there can't be. The definition of a bachelor is to be unmarried, to be an unmarried man, and therefore, there cannot be any married bachelor. A married bachelor is a contradiction in terms, so it cannot exist.
▶︎ 20:32 So you can know a priori without looking at the world, without doing any survey or any empirical, consulting any empirical information the exact number of married bachelors. There cannot be any. It's not that they're really, really rare and you have to really look hard and find a few over in the village somewhere. No, there can't be any. By the meaning of the words, by the way that these ideas relate to each other. If you find someone who says, "Yes, I'm a married bachelor," you wouldn't find, "Oh my God, this is incredible. We've got to do a study of this. How unusual." You would say, "You've misunderstood the words. You don't understand the meaning of these words."
▶︎ 21:23 To say that someone's a married bachelor is the same thing as saying that you found a four-sided triangle. It's not rare, it's not hard, it's impossible, because it's a contradiction. So there are certain, let's say, connections, certain statements that are answerable a priori. Because of the meaning of the words.
▶︎ 21:54 So if we say all bachelors are unmarried, we're taking, that's the subject, bachelors. That's the predicate, unmarried. We're connecting the two. But we're not exactly connecting them. See, this is what's interesting here. Because unmarried is already in the subject. If we were to really spell out what we mean, what we're really saying here is all unmarried men are unmarried. And you see unmarried is already in the subject. All we're doing is we're taking it out and showing it explicitly. And this is what Kant calls an analytic judgment.
▶︎ 23:00 We're taking a term, bachelor, and we're analyzing, we're pulling it apart and seeing what's already in it and just spelling it out. And you can know this completely a priori as long as you know the meaning of the words. It doesn't add any new information. My son, when he was younger, one time came up to me and asked me, "Daddy, what color is Clifford the big red dog?" And I thought to myself, "We're gonna have to keep him in the house for a long time. We're gonna be paying for that kid's housing for quite some time." Because it's in the name, the red, he's red. He's big. Assuming he's correctly titled, he's big, he's red, and he's a dog. You know all that just from his name. So those terms are all contained in it. You don't learn anything new. It just clarifies.
▶︎ 23:58 On the other hand, if I go back and say my dog Ned is brown, brownness is not a definition of my dog Ned. The dogs can be all kinds of different colors. Bachelors cannot have all kind of different marital statuses. The meaning of a bachelor, the definition of bachelor is to be unmarried. It can only be one way, and therefore we know this for sure because any other answer is a contradiction.
▶︎ 24:32 If we said some bachelors are married, what we're really saying is some unmarried men are married, and that's a contradiction. We're saying they're both unmarried and married as a contradiction. So any other answer is a contradiction, and we know that simply by the laws of logic, without looking at the world. But you cannot know what color my dog Ned is without looking at him or being told, because he could be brown, black, white, spotted, all kinds of different colors. There are many, many options here. There is no other option here.
▶︎ 25:20 So you learn something here, and this is what he calls synthetic, because you are taking something that is not in the subject and you are synthesizing it. You are combining it. You are bringing the two together so that now Ned is synthesized with brownness, and now this subject has a predicate that he doesn't have intrinsically in himself.
▶︎ 25:47 And you can see analytics are a priori. All you need to know is the meaning of the words. Synthetic are empirical. You have to check the world. A priori, analytic are necessary, absolutely necessary, because it can't be any other way. Any other option is a contradiction. Synthetic are contingent. They can mean lots of ways and that's why you have to go look at the word.
▶︎ 26:20 Now, we have two pairs and Kant sets up a table.
▶︎ 26:35 These types of judgments, these qualities, a priori, empirical, analytic, synthetic, they're mutually exclusive. It can be one or the other, and they're exhaustive. No other options here. So we have a priori and empirical, and we have analytic and synthetic. Two different pairs, so we have four different types of judgment and how we combine them.
▶︎ 27:16 Now, are there analytic a priori judgments? Yes, of course. The whole thing about how many bachelors are married, zero, that's analytic and it's a priori. So we have those. And we've already seen this kind of judgment. Think back to Hume. What did Hume call these? He called these relations of ideas. These are basically Hume's relations of ideas, a priori, uninformative, just the way the ideas relate to each other.
▶︎ 28:01 Can you have analytic empirical? Not really, because you just don't check the world for this. You don't use your senses. You just use the meaning of the words. There aren't any of these.
▶︎ 28:16 Synthetic empirical. Yeah. My dog is brown. This chalk is red. I am standing here. The vast majority of beliefs are synthetic empirical, and these are basically what Hume called matters of fact. This is what Hume was interested in. And Hume said these are the only two legitimate forms of knowledge. There's nothing else. Nothing else. Hume said that all legitimate forms are either matters of fact that we have experience of or relations of ideas that we take the ideas apart. Nothing else.
▶︎ 29:06 Kant says they're this type, there's a priori analytic, there's this type, synthetic empirical, and there are a priori synthetic judgments. That should be surprising. Hume based his whole philosophy on denying the existence of these. This is what metaphysics is. Metaphysics makes substantial claims, God exists, but without empirical information, without seeing, hearing, smelling, touching, tasting God. That is the nature of metaphysics, and that is what Hume tried to end, tried to show is impossible.
▶︎ 30:04 And here's where the disagreement with Hume begins for Kant, because Kant argues, no, in fact, there are some synthetic a priori judgments. Metaphysics does claim to be this type. And Kant's whole question of this book is, is that legitimate? But he does believe we have. We know we have legitimate a priori synthetic judgments. The question is not are they possible? The question is how are they possible? How can we do this?
▶︎ 30:53 Because it's weird. You should think to yourself that there's no way this could happen. You should, at this point, be a Humean. Hume gives a very common sense view. Yes, there are beliefs where we just take the ideas apart and we see how they go together. There are beliefs where we look and have experience and we see how things are, and that's it. There's no way to know the way the world is without looking at it. Very clear, very obvious, very common sense.
▶︎ 31:24 But Kant says it's wrong. Kant says there are ways to know facts about the world, facts, substantial, informative facts that don't rely on experience. This is how he's going to take that assumption and prove it. Instead of dogmatically assuming that how we think a priori is the way the world, is the way the world works, he's going to prove it. He's going to show why we can believe, why it is legitimate to believe that in certain cases, not very many, but in certain cases, we can examine the way our mind works and we can know if that's the same way that the world works.
▶︎ 32:26 And this is important. This is very, very important, because Hume showed us everything empirical is contingent. No matter how much data we have, no matter how long the string of experiences, no matter how stable it has been that a certain event has happened over and over again, we can never be sure that it will continue. Anything based on empirical experience is uncertain. Anything based on looking around us means that it is dependent on what the world shows us, and we don't know what it will show us.
▶︎ 33:24 The authority for empirical claims is the world, and we don't control that. So if the world shows us something surprising, we have to go with it. If the farmer comes out and grabs us by the neck, that's the new reality. That's the new normal. And for Kant, if we cannot know whether eating glass is harmful and eating bread is nutritious, then we're lost.
▶︎ 34:04 This is not just not being metaphysical. This is epistemological nihilism. This means there's no point in asking questions at all. There's no point in thinking. It's not a limitation, as Hume said. It means that we have nothing.
▶︎ 34:31 Tom Waits, he's a great, great musician, one of his albums, one of his best albums is titled Rain Dogs, and he's a fantastic lyricist. I read an interview with him one time and he explained what the title means, and he said, you know, dogs spend so much time going around urinating on their territory because when they do that, they know their way around. It's a way to make the world familiar, to make the world make sense, to know where things are, to be oriented, to have it be a home, where you belong. And then all of a sudden, every once in a while, it rains and it's all gone and the world's blank, and it's like all the signs, all the street signs have been taken down and the dog is in a completely blank world that smells of nothing.
▶︎ 35:32 That's the situation that we're in, Kant thinks, if Hume is right. We're just rain dogs and there's no way to know anything. And if that's the case, why are we doing any of this? Why are we thinking? Why are we doing experiments? It's just entirely pointless. Either it's possible for us to know something or give it all up, Kant thinks.
▶︎ 36:06 The question of the book is how are a priori synthetic judgments possible? Because we have them. We have two bodies of them we've known, math and science. Kant thinks that math and science are a priori, synthetic judgments because they are not contingent, because we know that tomorrow, the same causal links will continue. We know that nature will be stable. We can rely on it. That's the nature of science.
▶︎ 36:52 Science is not, "So far, things have been this way." That's not a scientific law. That's not what science gives us. If that's all that it's saying, and Hume thinks that's all that it can say, then it's not science. It's just rules of thumb. It's just history. So far, things have happened like this. If it's to be science at all, it must give us laws.
▶︎ 37:18 And laws have two crucial properties. Laws are necessary and universal. Science is never about one thing or two things. The lessons of Pavlov's dogs were not about Pavlov's dogs, they were not that particular group of canines. They're about animal minds, about dogs in general. Scientific laws are universal. They're about all of something, going forward in all places, going backwards throughout all time. That's what it is to be a scientific law.
▶︎ 38:10 And if we don't have that, then we don't have science, and if we don't have science, that doesn't... If we lose science for Kant, it's not just that we don't have people in white coats mixing beakers together. It's that we don't know what to do. We don't know how to build a building. We don't know how to cook a meal. We don't know how to speak. We don't know if anyone around us is human. We lose everything. So it all rides on a priori synthetic judgments. It sounds very technical, sounds very dull. It's not.
▶︎ 38:57 It's everything. And Hume has left us in a position where it seems fundamentally impossible. But that's actually a good thing. The fact that a priori synthetic judgments are so weird, they seem so impossible, means they are a fantastic clue for critical philosophy. Kant is the one who came up with the term critical philosophy, where he's trying to understand the nature of the mind, the structure of the mind, how we think, how we reason, in order to understand the limitations. And again, drawing that line both tells us what is inside that line, what we can think legitimately, and what is outside, what we cannot.
▶︎ 39:55 And it's very, very hard to figure out how our minds work. But if we have this one thing that is bizarre, that is ridiculous, that is weird, that means that whatever the mind is like, it must be such that it can do this thing. That the model of the mind that we come up with has this requirement. It must be able to produce a priori synthetic judgments.
▶︎ 40:33 So it's a really, really helpful clue. In one sense, it's incredibly challenging because it seems impossible. On the other hand, it gives us enormous guidance because we know what we need to do. We know what the requirement is. We have to come up with a way the mind works such that it can do this. And that's what he's going to give us. And in order to explain that, I have to tell you a riddle.