▶︎ 0:00 Welcome everybody to my little course on Plato's Theaetetus. My name is Richard Polt. I've been teaching philosophy at Xavier University for over 30 years, and this is a platonic dialogue that I've taught almost every year, and I don't get tired of it. I keep choosing to teach it because it's not only conceptually fascinating and has some really deep arguments, but as a piece of drama, it's really entertaining and fun. And every time I teach it, there's some unexpected insights I get or questions that I get, and it's just a great conversation starter.
▶︎ 0:34 So I've designed this course to be an introduction to the Theaetetus, or to Plato, or in fact of philosophy in general, because the question of the nature of philosophy comes up at several points directly in the dialogue, and it's always implicitly there as well. So I think it's a great first text in philosophy. I'm not a Plato specialist or expert, and so you should all be challenging me for the totally clear conscience. "Wait, you missed this." Or, "You didn't realize this." In fact, I hope that I'll learn from you.
▶︎ 1:07 My main specialty is actually Martin Heidegger, a twentieth century German philosopher, but so my exposure to Plato is through, as a devoted and loving reader of several favorite dialogues over many years, but not as a scholar. So we're gonna have a spontaneous dialogue, improvising, surprising, and we'll see where it goes. This is food for thought. That's what I think the purpose of Plato's dialogues really is, food for thought for an individual reader or for a group of readers such as would have been there in Plato's school, the Academy, and who would have had, I think, lively conversations, maybe based on his writings.
▶︎ 1:47 So the teacher in the room really is Plato, but he's thousands of miles away, and more importantly, thousands of years away. And another problem is that he never actually says anything directly in this dialogue or in any of them. So before we get to page one, I wanted to talk with you a little bit about how to read an odd writer like this.
▶︎ 2:10 What we have from Plato is a set of letters, but mostly dialogues, which are philosophical plays, in which Plato himself is hardly ever even mentioned. In the dialogue, the Apology, representing Socrates' trial, Socrates refers to Plato here. And in the Phaedo, which is about Socrates' death, the narrator says, "Oh, Plato couldn't be there. He was sick." Which is crazy. How could he miss the death of Socrates? So he's deliberately taking himself out of the dialogues. And instead, the main speaker usually, the hero of these things, is Socrates.
▶︎ 2:51 Socrates was Plato's mentor and teacher and hero, and he died when Plato was in his 20s. He did not die a natural death. In case you don't know, he was put on trial, charged with impiety and corrupting the youth, which are always good charges against philosophers. In fact, recently in Texas, a professor was banned from teaching Plato's Symposium because it espoused "radical gender ideology." So Plato is still corrupting the youth, I'm happy to say.
▶︎ 3:26 So Socrates is the main speaker, or the hero, if you will, of most of these dialogues. But you shouldn't necessarily believe what he says or think that he has good arguments. In fact, I think often we're supposed to see that he doesn't have good arguments. He's also ironic, he's playful, he's messing with people's minds, so you can't trust anything he says and I don't think you're meant to.
▶︎ 3:53 How should we read these things? I wanted to run a few things by you that Plato says about writing. In the seventh letter, which is the most interesting and important and longest letter that we have by Plato, he says, "I've never put my thoughts into writing and I never will. I'll never be so crazy as to do such a thing." Because writing is at many removes from reality. There's the real thing, let's say circle, as understood by geometers, and then there's various levels such as the definition of a circle, or the image of a circle, or physical approximation of a circle, and the words we use to describe these things, and then writing puts those words into a text. And so if you think that reality itself is contained in a book, you're deeply confused.
▶︎ 4:46 There's also a dialogue named Phaedrus where Socrates talks about writing. He says that writing was invented in Egypt by a god named Famous, who brought this wonderful new invention to the King of the gods, Thoth, and said, "Look, I've discovered a potion for wisdom and memory." And Thoth says, "No, you've discovered a potion for foolishness and oblivion." Why would he say such a thing? What do you think? And what about memory? Why is writing actually potentially harmful to memory?
▶︎ 5:30 Audience: Because then we can't memorize. We're less inclined to put in the work to memorize texts in our brain if we know that it's already accessible here.
▶︎ 5:41 Yeah, exactly. This has been empirically proved. So for instance, certain old, noble families of Rajas in India, they would have these sort of family bards who would compose epics about the exploits of the family, and they were traditionally just oral bards. They were illiterate. So some bright colonial person had the idea of, or, I think this was actually more recently. They had the idea of teaching these bards to read so that we could, and write so we could preserve these wonderful epics. And pretty soon, they couldn't handle reciting these things by memory anymore. They had to, they didn't know it by heart, they had to look at the text. So there's truth in this.
▶︎ 6:25 And Socrates goes on in the Phaedrus to talk about some liabilities of writing, as opposed to oral speech. First, if somebody has a question about the book that isn't directly answered in the book, the book just sits there, it can't defend itself. It just keeps repeating the same thing. So it can't respond to a particular challenge, and it also can't speak differently to different people, which a skilled rhetorician would do. You tailor your speech to the person you're speaking to, and the book just says the same thing to everybody. So Socrates says, "No serious person would take writing very seriously."
▶︎ 7:08 Now, of course, Plato then wrote 2,000 pages of dialogues, so is he just confused or what's going on here? Why is such a great writer writing about the futility of writing?
▶︎ 7:24 Could it be deliberately ironic on Plato's end? Because Socrates isn't there to defend himself. And also, do we know if he really did say that? We don't know anything for sure about what Socrates said. We have three original sources about Socrates. There's Plato, there's Xenophon, who's a similar writer, but most people say less deep, and there's Aristophanes, who's quite different. He's a writer of comedies who published, or produced The Clouds during Socrates' lifetime, and it's a very different portrayal, a comic attack on Socrates. So most people would say these are imitations of the way Socrates used to operate, but we shouldn't take them too literally.
▶︎ 8:10 And Socrates himself did not write anything, which goes hand in hand with his frequent saying that he didn't know anything, so why would you put it into a text? What if Plato is writing in a way that tries, to some extent, to get around these limitations? You can't perfectly get around them. They apply to all sorts of recording. For instance, this is going to be filmed and put online, and we have no control over who's going to watch it, what they're going to say, whether they're going to think we're a bunch of idiots, we can't defend ourselves, we can't speak to them. So these are real limitations, but how could you partially get around them in writing?
▶︎ 8:56 By the way, those who are watching should understand that this course is divided into five sessions, and we're reading roughly a fifth of the dialogue each time, and those in the room, I've asked them to read only up to that point so that we maintain a little suspense and we won't have any spoilers. So what about this suggestion? And then we'll get into the actual dialogue. But you can't anticipate in advance how many exact psychological types of people over several thousands of years will pick up your book, but maybe you could differentiate at least between those who are surface readers and those who are critical readers.
▶︎ 9:36 I think Plato tries to do that. Or at least, I can't read the man's mind, but I do realize that when you question and criticize what's in the text, often you make really interesting discoveries that tie in very nicely to other parts of the text. So at least, I think he's differentiating between those two kinds of readers, the philosophical and the non-philosophical reader, if you will, and sending, perhaps, different messages. So, on some theories of how to read Plato, this is crucial. You have to distinguish between exoteric and esoteric teachings.
▶︎ 10:15 So let's start, and our assumptions will be that, well, first of all, let's assume he's a genius, whether he's in total control or not, so every word counts. There's a reason why everything was put in, and everything can be questioned and should be. So it begins with a little prologue, and we are using, by the way, the translation by M.J. Levitt, revised by Miles Bernier, published by Hackett, but those who are watching may use any translation. And we'll refer to the text by the marginal numbers and letters, which are called Stephanus numbers after an early printed edition of Plato.
▶︎ 10:56 So it begins with a couple of pages of prologue where you have these characters Euclides and Terpsion, and it turns out that Euclides has a text which then most of the dialogue goes on to recount. So what did you all get out of these first two pages? Why are they there? Why, assuming that Plato had some good reason for including them, what do they give us?
▶︎ 11:24 Audience: Well, they're talking a little bit about Theaetetus himself, and giving, if not foreshadowing, just giving a little preview of who this young man might be.
▶︎ 11:40 Right. So what are his characteristics? I'll just abbreviate him as THT.
▶︎ 11:45 Audience: The prologue mentions that he was a soldier involved in some sort of a battle, and behaved bravely or behaved well, and the speakers were indicating that they were not surprised to hear that, so apparently, they had expected that from him.
▶︎ 12:05 Right, so he's made a reputation for himself as a courageous man. Not as a mathematician. He's not mentioned in his capacity as a mathematician. No.
▶︎ 12:14 Just as a warrior. What about Socrates? What did we learn about him? Socrates had a conversation with him, but unsurprisingly, Socrates had not written it down. But Socrates must have a great memory, because he was able to recount it all from his natural memory to Euclides, who then tried to get it all down on papyrus. So, a great memory. And any other strengths of Socrates? He's called a prophet, because he had a sense even then of what a fine person Theaetetus would be, I would say.
▶︎ 12:55 And Socrates is prophetic in what sense? He prophesies about Theaetetus. That that week they would hear, he would be acclaimed for some reason. We would hear more about him once he grew up. So I would say he's a good judge of character. Yeah, so we'll hear much more about Theaetetus, he says, "If he lives."
▶︎ 13:27 And death seems to be hanging over these first couple of pages, rather darkly. Theaetetus seems like he's on the verge of death. Socrates is long dead, and this whole conversation apparently happened shortly before Socrates' death. Socrates says, if he lives, we'll hear more about Theaetetus. Yeah, there's a lot of doom here, and it makes me wonder whether this is going to be a tragic dialogue. But we'll see soon that it's not. It's actually quite funny.
▶︎ 13:55 One more thing we could think about with the first few pages is, this is gonna be a dialogue about the nature of knowledge. I think Plato usually tries to show that these philosophical questions come out of real life. They're not just dreamed up in an armchair. So the characters, I think, are illustrating how we actually are concerned with knowledge in a daily way. "Are you only just in from the country, Terpsion, or have you been here for some time?" Natural question to ask.
▶︎ 14:24 They're trying to get knowledge about where he came from, the chronology, and they're looking into causes of things, they're trying to figure things out. They're using their memory, and so on. And this will all be considered again on a more theoretical level.
▶︎ 14:41 In the opening of the main dialogue, Socrates runs into Theodorus, apparently in a gymnasium, and now we find out that this could be a comic dialogue, in fact. I think it's pretty funny. Socrates says that the one kind of knowledge he's always trying to get is knowledge of which particular individual young men are promising in Athens, and Theodorus says, "Well, there's this one boy I've been teaching, and wow, he's fantastic. In fact, people might think I was in love with him or something if he didn't look like you. Although he's not quite as ugly as you." Maybe this is the sort of thing you could say without being rude to a good friend, but he didn't get off on the best foot, I would say.
▶︎ 15:24 I appreciated that comment though, because it gives us a sense of what Plato is saying people said Socrates actually looked like, physically. Because I don't think there are many descriptions of Socrates in Plato or elsewhere, so this is one talking about him being snub-nosed. There are a few in Plato, and he's usually described as very unattractive by Greek standards, and yet fascinating, and in fact, erotically fascinating.
▶︎ 15:58 In the Symposium, Alcibiades, who is this very charismatic, very handsome, fascinating character, he says, "And I'm obsessed with this Socrates, and I really want to get with him, even though he's so ugly. But on the inside, he's wonderful." And apparently they spent a whole night together and Socrates never touched him, which drove Alcibiades really crazy.
▶︎ 16:21 Theodorus goes on to describe the personality of Theaetetus, and it's a nice little description of what it takes to be a good learner. You need to be both sharply intelligent and very dedicated and steady, which he says is a rare combination.
▶︎ 16:37 And at 144b, Socrates asks, "Whose son is he?" Theodorus says, "I've heard the name but I don't remember it." It's interesting, and I think it will prove to be relevant later on. Theodorus is a little oblivious to the concrete details of peoples' lives. And in contrast, Socrates says, "Oh, I know him. He's the son of Euphronius of Sunium." He doesn't happen to know his name, but he knows all about his family, bearing out the point that Socrates, as he said at first, is always interested in the particular individuals who are promising in Athens.
▶︎ 17:18 And here's where the question of knowledge comes up. Again, based on real life. Because Theodorus is a teacher trying to convey knowledge. Theaetetus is trying to get knowledge. Well, what is this thing that we're involved in? Why are we here? What are we aiming at? And then in 145d, very quickly, Socrates touches on wisdom and identifies it with knowledge. D and E. And implicitly, philosophy is there too, because the word philosophia means love of wisdom. So what's at stake here is what we're even trying to achieve when we philosophize.
▶︎ 18:02 In 145e, he says, "Isn't it the things which they know that men are wise about?" Well, yes. So knowledge and wisdom will be the same thing. Now, does this logically follow? It's the things you know that you're wise about, so knowledge is wisdom. But I think clearly, they're different. Even if we think of wisdom as expertise, I could know a few facts about Manhattan, for instance, but not be an expert on it. Another good analogy is, it's the things that you hear that you can listen to, therefore hearing and listening are the same thing. No, not at all. It could go in one ear and out the other, so listening is an extra level, if you think about it.
▶︎ 18:51 When things like this come up, I'm always reluctant to assume that Socrates is confused or Plato is confused. If we can figure this out in a few minutes of reflection, surely Plato could figure it out. But he will put things into dialogues that, this is an example of what I said about addressing different audiences. If you're not very reflective, this sort of washes over you, "Oh, sure, knowledge and wisdom are the same thing." If you are, then you start to think more deeply about wisdom, therefore about philosophy, and it gets you somewhere else.
▶︎ 19:24 Socrates then goes to, "Well, all right. Let's define knowledge. Let's put it into words." And it's not an easy thing, but Theaetetus does give an answer, 146C: "I think that the things Theodorus teaches are knowledge, I mean, geometry and the subjects you enumerated just now. Then again, there are the crafts, such as cobbling, whether you take them together or separately." So he's giving examples instead of a general definition.
▶︎ 19:56 And there are other dialogues where this happens too. He'll say, "Well, what is virtue?" "Well, there's women's virtue, there's men's virtue, there's children's virtue." No, but what is virtue altogether? This is another move that could be questioned. Some people call it the Socratic fallacy. Why can't these things belong together in a sort of rough, family-resemblant sort of way without all having some identical feature? Well, maybe they do, maybe they don't.
▶︎ 20:25 Also, Theaetetus did start to make an interesting distinction between theoretical sciences and skills, know-how, knowing that and knowing how, and you could maybe explore that. But Socrates doesn't choose to. Another thing to think about at this point is, when he compares it to clay, in 147A and B, clay of the potters, clay of
▶︎ 20:52 The stove makers, clay of the brick makers. Well, if the person doesn't know what the word clay means, that's not going to help. Do you think anyone can understand the name of a thing when he doesn't know what the thing is? No. Now, is this really the case when it comes to knowledge though? Maybe somebody learning Greek might never have run across the word for clay before, but they all speak Greek, it's not a question of a foreign language, they're asking what is knowledge. Is this a totally foreign concept to them?
▶︎ 21:23 I had a problem with this part of the argument here, because Socrates then goes on to say, this is 147B, "Then a man who is ignorant of what knowledge is will not understand what cobbling is, or any other craft." So you imagine a cobbler, and you go to the shoe shop and you say, "Hey, cobbler, can you give me a working definition that encompasses all knowledge?" And he says, "Get out of my store." Does that mean he will not be able to fix your shoes? The cobbler could still certainly fix shoes without being able to define knowledge or define cobbling even, but Socrates isn't asking for a practical result. He's asking for a conceptual clarity.
▶︎ 22:12 Heidegger talks about this by the way. He says, "In everyday life, we're not forming these theoretical abstractions and objective statements. We're using things and there's a kind of clarity and know-how that goes along with just using things, and then the insistence on objectifying them may be a fatal error."
▶︎ 22:30 There's also an odd sort of self-referential moment here when Socrates says, "So a man who doesn't know what knowledge is will not understand knowledge of shoes. A man who is ignorant of what knowledge is will not understand what cobbling is." Now, notice how he used the word know in reference to knowledge. We know what he means, sort of, when he says we don't know what knowledge is. Later on, he'll refer to this sort of thing as shameless. How can we shamelessly use this word know when we don't even know what it... But is it really possible to avoid this? Can we just start from scratch without using these concepts that have not been defined yet?
▶︎ 23:13 So there is a circle there, but maybe it's not a vicious circle, maybe it's a virtuous circle, because you've got to start with what's familiar to you and what you "know," and then you try to deepen it and you try to clarify it. Maybe you never finish, but it's just something to keep in mind, that they're using the word know all the time and maybe we can't avoid that. And in some sense, the answer to what is knowledge is already within them. It's got to be because they're using the word and it means something. So at least some sort of answer, maybe not the right one, is already within them or they're pregnant with it.
▶︎ 23:47 Theaetetus understands now what kind of answer Socrates is looking for. He's looking for a general answer, and we learn that he's rather good at math in the next bit, because Theodorus demonstrated a point about certain quantities and then Theaetetus and his friend, confusingly also named Socrates, generalized this into a general rule. So let's say that there are three squares and this is their area. A one square foot square, three square feet, five square feet. And the question is whether the sides of these squares are commensurable.
▶︎ 24:33 The side of the one-foot square is obviously one. The side of the three-foot square is obviously square root of three. But what does that mean? What is the square root of three? Is it commensurable with one? If it's commensurable, this means that you can express it as a ratio of two whole numbers. It's a rational number.
▶︎ 24:56 So is the square root of three, for instance, I don't know, seven-eighths? Is it eight-thirteenths? Is it 143, 268ths? It's none of those actually, and the Greek mathematicians, a great achievement was to show that there are irrational numbers. You cannot express them in a logos. This will be an important word later on. Very fundamental Greek word that means language, reason, but also ratio. Actually, ratio in Latin also means reason, ratio.
▶︎ 25:33 So an irrational number cannot be expressed as a ratio of two whole numbers. And the fact that these numbers, that these quantities exist was rather mind-blowing for the Greeks because they wanted those explicit statements that you were talking about. Typically, they want things to come down to something that can be articulated and precisely defined, and you cannot do that with an irrational number. So maybe this is a hint perhaps that what is knowledge is also going to turn out to be irrational in the sense that you cannot at least fully give a logos of it, an account of it.
▶︎ 26:16 Theaetetus was able to give a general mathematical account. Basically, he's saying that either a number is the square of some natural number or the square root of that number is irrational. And yet, he says, 148B, "Socrates, I shouldn't be able to answer your question about knowledge in the same way." Theodorus turns out to be a false witness.
▶︎ 26:43 Now Socrates says, "No. Come on, put your heart into it. This isn't really a small thing. Of course, this is a big thing. You can do this. And the fact that you have been wondering about it and worrying about it is an excellent sign. Those are labor pains. You're pregnant." And here's this wonderful extended metaphor in which Socrates compares himself to his mother, who apparently was a midwife with the wonderful name Phainarete, meaning she who brings virtue to light or virtue shower, which goes along with his frequent statement, "I know that I know nothing." It's a good description of his practice.
▶︎ 27:26 And he says he can't have babies anymore, just as midwives would be older women past menopause. He can't give birth to any theories. He's had some in the past. He has experience giving birth to theories, but none of them have worked out, and so he possesses no wisdom. So it's maybe psychological knowledge that he has, or knowledge of. It fits with what he said at the beginning of the dialogue. "I'm always trying to get knowledge about particular promising individuals." And so he has a knowledge of character, just as they said in the prologue. He has a good insight into particular humans and human situations, even if he doesn't know general abstract answers such as what is virtue, what is knowledge, what is being, and so on.
▶︎ 28:10 Another nice detail about the metaphor is, he says, and everybody seems surprised by this, that midwives are good matchmakers. Maybe he's made this up. He says he's also a good matchmaker, and this is a comic moment. "Sometimes I meet guys, and they just don't seem to be pregnant. So I need to send them off to somebody like Prodicus to get knocked up." Prodicus being a sophist. And since we're going to meet another sophist in a minute, I should say something about that.
▶︎ 28:40 If philosopher means lover of wisdom, sophist means wise guy. And these wise guys would travel around Greece and they would teach on all sorts of topics, but especially rhetoric, the art of persuasive oratory, which could get you quite a bit of power in a democracy like Athens where every citizen had the right to speak up in the assembly and try to persuade people. So Prodicus was one of these people full of ideas that might get somebody philosophically pregnant.
▶︎ 29:10 Audience: Isn't there another issue there that he talks about the distinction between being a matchmaker and being a procurer. And then he just leaves it alone and doesn't really say which one he is. So he's sort of leaving it out there, that he might be a sophist too in some sense.
▶︎ 29:38 Right. He'll make sophistical arguments sometimes. We just saw him make one. "You can't be wise without knowing something. Therefore, knowledge is wisdom." That's sophistry. So maybe both the sophist and Socrates make bad arguments.
▶︎ 29:54 Audience: Do they have different intentions? Are the sophists more greedy or selfish in their intentions?
▶︎ 30:01 Anyway, you can see why Socrates would be accused, not without reason, of corrupting the youth and undermining solid, good, healthy opinions through verbal trickery. So in general, the effect of the midwife metaphor is to encourage Theaetetus. "You've got some answer within you, and I'll help you give birth." So we finally get a proper answer.
▶︎ 30:28 This is in 151E, when Theaetetus says, "It seems to me that a man who knows something perceives what he knows, and the way it appears at present, at any rate, is that knowledge is simply perception." Doesn't he also use the same word in various ways in what he's saying? "It seems to me," which is a perception, "A man who knows something perceives what he knows, and the way it appears at present," which is another form of perception, "is that knowledge is simply perception." So he's doing the same thing in a way that Socrates did earlier. He's using the same word to define itself. That's great. So his definition is illustrating itself in a way.
▶︎ 31:17 Audience: In the way he expresses it, right?
▶︎ 31:20 Appearance goes hand-in-hand with perception. And he says, "As it seems to me right now, as it appears to me right now, perception is nothing but, or knowledge is nothing but perception." The Greek words, in case anybody's curious, knowledge is episteme. Sometimes philosophers talk about epistemology, the theory of knowledge. Perception is aisthesis, as in esthetics, if you think about beauty and art as being about how you feel, how you perceive things. And there's the word phainete, "It seems, it appears to me."
▶︎ 32:01 So these are all related. He's illustrating his belief, it seems, in the way he expresses it. The way it appears at present is that knowledge is simply perception. And appearance is always in the present, right? It's appearing now, and then it disappears and something else appears. But he's saying, "This is how I now perceive knowledge." So he's not quite sure.
▶︎ 32:26 And isn't this almost a self-refutation right here? Because he's saying, "Well, right now the way I perceive knowledge is that it's the same as perception, but I don't know."
▶︎ 32:37 Audience: Yeah, he's...
▶︎ 32:38 He's ready to get sort of slapped down.
▶︎ 32:41 Audience: Slapped him.
▶︎ 32:42 Because he doesn't really believe knowledge is perception. He just told us that because he's saying, "Here's how I perceive it, but I don't know if I'm right." And so that means he doesn't really know himself. He doesn't know where he stands on things.
▶︎ 32:56 Now, he did have a mini argument for his view though. He said, "A man who knows something perceives what he knows. So knowledge is perception." How's that? Nice sound argument? It should ring a bell.
▶︎ 33:11 Audience: Well, it's just like what you said earlier about knowledge is the same as wisdom.
▶︎ 33:18 This is like an echo effect. So just to symbolize this for a moment, Socrates said, "If you have wisdom, therefore you have knowledge. So wisdom and knowledge are the same thing." Bad argument. And now Theaetetus is saying that, "If you know something, then you perceive it. So knowledge is perception." Seems Socrates set a very bad example, maybe on purpose. But Theaetetus is now reproducing the same invalid argument.
▶︎ 34:08 But Socrates does not tear it down. He praises it because this is what he wanted. He wanted Theaetetus to give birth to something like this. Now, the birth process is not quite ready. The baby's crowning. It's not yet delivered. We don't really know what this means to say knowledge is perception until we look at some of the implications of this and how it would be applied in some situations and how it would answer some rather obvious objections.
▶︎ 34:36 So it's going to take a while before Socrates says, "Okay, now your firstborn baby is here. Now we're really going to test it and see whether it's true or false." And by the way, we should remember that a difference between Socrates and a midwife is that a baby is a baby. Even if it's a stillbirth, it's real. But a theoretical baby, an idea may be just a wind egg as he puts it, an infertile egg, or a nothing, a nothing burger, we would say.
▶︎ 35:07 So Socrates praises this, and he immediately connects it to the view of Protagoras. Protagoras was another Sophist, maybe the most famous of all the Sophists. It was said that he had no fixed fee for his teachings, but he would ask those who studied within to go to a temple and swear to the god that the teaching was worth so-and-so much gold that they would deposit there. And in this way, Protagoras became very wealthy because people thought his teachings were so valuable.
▶︎ 35:40 The statement that we have from Protagoras, and the direct statements we have about him are almost exclusively due to Plato. The statement is, "Man," meaning human beings, the human being, "is the measure of all things, of the things which are that they are, and of the things which are not that they are not." This could be read in many ways. How does Socrates interpret it, and what does he think that Protagoras means? Well, he's basing everything, he's interpreting this as basing everything on each individual's experience. In this case, the sense experience.
▶︎ 36:26 And so that fits what Protagoras is saying. "My experience as one human being is the measure of all things," in my mind anyway. So in this reading at least of Protagoras, it means each individual human is the measure of their reality. And then there is no reality in itself. Is the wind in itself warm or cold? The question doesn't even make sense. There is no warm and cold except in relation to a perceiver. There is no temperature of the wind in itself. In fact, there is no wind in itself.
▶︎ 37:04 You can quickly see that this is going to become rather weird. So at first it seems sort of initially plausible I think to say knowledge is perception. Yeah, the way you've, the way things seem to you, the way things are perceived is what you know. Seems fair enough, but very soon you see the implication that then there is no absolute reality, that there is no being in itself of anything.
▶︎ 37:27 If a tree falls in the forest and nobody's listening, the tree doesn't even fall in the forest. There is no tree, there is no forest, unless some human or maybe some animal is perceiving it. When I first read the Theaetetus, it was taught by Paul Feyerabend, who is a brilliant philosopher of science at UC-Berkeley, and the main thing that he focused on was some uncanny parallels between this ancient notion and quantum mechanics.
▶︎ 37:58 There's some issues at the quantum level that I'm not an expert on by any means, but for instance wave-particle duality, is something like light, does it consist of photons, particles of light, or does it consist of waves in some sort of medium or maybe without a medium? Well, it depends what experiment you do, and some experiments have to mean that it's a bunch of particles. Others have to mean that it's a bunch of waves. Which is it?
▶︎ 38:29 Well, Protagoras would love this. He would say, "What do you mean which is it? It's nothing in itself. It depends on what the observer perceived and how they perceived it," and that was the perception to that perceiver or that experimenter at the time.
▶︎ 38:44 Yeah. Or the uncertainty principle on some interpretations means there is no such thing as the position and velocity, and mass of a subatomic particle that coexist at the same time. Some of them are just undefined and indeterminate and non-existent because they're not what you're testing for, and only in the experiment does the reality emerge.
▶︎ 39:12 Now are we clear on why Socrates immediately dragged in Protagoras? If you say knowledge is perception, why does it follow that everything is relative to a perceiver and there is no absolute knowledge, or no absolute objective being of things? Well, I think it's implicit in the statement. I perceive something so I think it's knowledge. If that's the standard of knowledge, then any perception can be state to be knowledge, which means what we were just talking about becomes true.
▶︎ 39:52 There is no absolute reality and there's only what you perceive it to be. And we assume that knowledge is true. This is going to be taken for granted throughout the dialogue. Doesn't make sense to talk about incorrect knowledge. We would talk about incorrect opinion or something.
▶︎ 40:10 And then there can't be any things-in-themselves because, let's say if there were a pen in itself apart from my perception, then my perception could be more or less close to reality, it could be deviating from reality, it could be incorrect. But if there is no pen in itself, there's only what appears to me, I can't be wrong. So that brings us through Theaetetus 152C, and then in our next session, we'll look at more developments where he connects this idea that knowledge is perception to some more theories till the baby is fully born and ready to be tested.