Plato's philosophy

We can explain Plato's analysis of the concept of "knowledge" in this way. Take the sentence "P knows X" as an example (P is anyone and X is any fact). What is the prerequisite for this sentence to be established? First of all, "P believes X" must be true. You can't claim that you know something and at the same time claim that you don't believe it. I can only think of a counterexample, that is, if someone knocks on your door, when you open it, you may say, "joe smith, I can't believe it's you!" But, in fact, you believe it. Otherwise, you can close the door and go back to watch TV. Therefore, "belief" is a necessary part of knowledge, but it is not the whole knowledge. So, what do you need besides believing? We need facts. X must be true. No one will come to the conclusion that the earth is flat, because it is not. Even if thousands of people claim that they know that the earth is flat, we know that they are all wrong. C.S. Lewis once pointed out that before Columbus, people didn't think the earth was flat, not because they thought it was round, but because they didn't think of it at all. So now we come to the conclusion that:

Know that the earth is flat

Rotate into a pear shape at the speed of 1000 km per hour.

Here, (a) and (b) are both necessary components of knowledge. But are these enough? In other words, do truth and belief constitute knowledge? Plato's answer is no, more or less for the following reasons: suppose you ask me if I know that the earth is round, and I answer yes. Do you believe that the earth is round? Believe. Is the earth round? Yes, I deliberately ignored the fact that the shape of the earth is actually a bit like a pear. If you spin at a speed of/kloc-0.000 miles per hour, you will also become a pear. But why don't these constitute knowledge? Suppose you ask me how I know that the earth is round, I will say, "Look at the soles of your feet. Do you know how they arch? Now I ask you, if the earth is flat, will God give us arched feet? " You will immediately realize that I didn't know the earth was round. I just got lucky and got it right!

So, if facts and beliefs are not enough to constitute knowledge, what conditions are enough to constitute X knowledge?

The Greek word "logos" is the source of the word "logic" and all terms ending in "-logic". For example, biology is a theory or research about biology; Sociology is a theory or study about society and so on. Therefore, to give the logos of X is to give a theory or research result to explain X. In Greek, "logos" also means "discourse", and people must be able to tell what that theory is. If someone tells Plato or Socrates that he knows the answer to the question but can't say it, Socrates and Plato will accuse him of proving that he doesn't know the answer.

For Plato, the logos of X is given to prove the rationality of your belief in X, but for him, knowledge is the belief that has been proved to be reasonable. This conclusion seems quite perfect, but, as we have seen, in Plato's view, the concept of "confirmation" is quite technical. In fact, it is more technical than the analysis revealed before, which will be found when we discuss Plato's famous "line metaphor" It is the core of Plato's most important book, The Republic. It is called "metaphor" because knowledge and reality are connected by a line, which may have been drawn on the ground by Socrates with a stick. What we get from it is Plato's metaphysical system. On the right of the line is his ontology (his ontology), and on the left of the line is his epistemology (his epistemology). At the same time, line metaphor also implies ethics and aesthetics. Let's focus on the left part of the line metaphor, because it corresponds to the theme. However, in order to discuss this part better, we must first explain the ontological part of line metaphor.

The visible world (that is, the material world) can be regarded as representing the changing world of Heraclitus. It consists of "image" and "sensible thing". These two parts are constantly changing.

picture

Plato gave us some examples of images: shadows and reflections. They are all images of perceptual things, and they all depend on perceptual things. In Plato's view, the shadow of a tree is not as real as a tree, not only because a tree is more durable than its shadow, but also because a tree can exist without a shadow, and a shadow cannot exist without a tree. Now let's turn to the left of this line. In this part, there is nothing (such as shadows or trees), only the state of mind, that is, the state of consciousness. If the object of your consciousness is an image, then you are in an imaginary state. The Republic implies that this state is an illusion. People in this state will confuse images with things. Have you ever been attracted by someone's photo, or shouted "No.9, shoot!" When watching a football match on TV? No? This kind of thing has never happened to me, because we study philosophy after all! )

A wise thing

Perceptual things are individual things in the material world, such as trees, books, cats and so on. They are more real than images, but they are not absolutely real, because they are not eternal. This is not only because they are not eternal (trees and cats will die of old age, books will fall apart or be burned), but also because they are dependent. They rely on the sun first. If the sun is close to the earth, everything will burn; If you are farther away, everything will freeze; If it doesn't exist, trees, books or cats and their images will disappear. Moreover, perceptual things also depend on form, as we will see later.

Go back to the left of the line. If the object of your consciousness is perceptible, you are in a state of faith. Imagine that we saw an animal in the field and asked the local farmers what kind of creature it was. He said, "This is a horse." You asked him how he knew it was a horse, and he said (no doubt impatient), "This is a horse! You see, a horse is a horse! " Well, the farmer believes that this is a horse (belief) and it is indeed a horse (fact). Why did Plato say that the farmer didn't know it was a horse? Because the farmer didn't give the sign. What do you mean, give it to logos? Maybe so, you ask farmers:

This man knows what a horse is. He can grasp the individual perceptual object at a higher level, that is, the conceptual level. Of course, there are still many problems, including elitism According to this explanation, there are thousands of people who have dealt with horses in Qian Qian, and only a few carefully selected people know what a horse is-Plato is not one of them! Besides, if you don't have a slice of a horse and don't know biology and chemistry, it's hard to believe how you know what a horse is. In fact, it seems that things have become like this, that is, if people want to know anything, they must know everything. Some interpreters think this is Plato's problem. But at least it can explain Socrates' ignorance assertion.

concept

Therefore, we have understood that people can leave faith and move towards understanding (and thus rise from opinions to knowledge) by grasping perception at the conceptual level, that is, by attributing particularity to universality. As a result, people have gone beyond the changing world of Heraclitus and entered the eternal world of parmenides, namely "knowable field". By putting the objective object in the context of logos, theory or science, people elevate the objective object from the ever-changing material world and make it stable. Let's take an example and imagine three different life segments: (1) Your pen falls from the table to the ground; (2) A meteor passes through the atmosphere and emits a silver spark in the night sky; (3) In the sixth round of heavyweight boxing, the defending champion got a fatal uppercut on his chin and fell to the ring like a pile of bricks. The description of the image in each example is very different (this is the perceptual level); But in order to understand these three events, we also need the theory discovered by Sir isaac newton: the gravitational force between any two massive objects is directly proportional to the mass of these two massive objects and inversely proportional to the distance between them. This is knowledge. But for Plato, this is obviously not the highest kind of knowledge. We also need to discuss pure reason.

idea

Plato believes that the concepts we just discussed (horse, gravity) are not only abstract concepts in specific situations, but replicas of higher truths. He called these higher truths ideas. Idea is the prototype of everything in the visible world. They exist outside time and space. They are neither material nor spiritual. In other words, they don't just exist as ideas in people's minds. Because it is not material, it cannot be captured by emotion; But even if they are not spiritual, they can be grasped by reason outside the sensory world. These ideas are true in an eternal sense, because they cannot be created, destroyed or changed. But it should be noted that they are not absolutely correct, because they still depend on Plato's "goodness", just as sensible things depend on the sun. Goodness seems to be a supreme idea, the idea of all ideas. It is an absolute value, which makes all reality rooted in it and gives it value.

This is the same as the role of God in ontology in the late Middle Ages. Remove the letter "O" of "good" and you will become a god. Changing the "U" in "Sun" into "O" will become the son, so that we can have a general understanding of Platonism in medieval Christianity. "Goodness" is the core of the whole Plato system. The center remains unchanged because of the persistence of goodness. Goodness has the eternal characteristics of parmenides. If it can't stay the same, we will fall into the changing world of Heraclitus.

How does thinking grasp the train of thought? We can only do it if we completely transcend our feelings. Feeling is always committed to creating the world to some extent, so it is essentially opposite to becoming the world. Although the concept really belongs to the knowable field, it is still limited by images, so it is still polluted to some extent. (Note that prejudice against the body came into western philosophy with Plato. This is not characteristic of Greek culture at all. The social practice, art and even religion of Greek culture showed no contempt for the body. ) When you face Newton's definition of gravity ("Any two massive objects ……"), what you see in your mind are two massive objects. However, when thinking is liberated from the visual image, it grasps the form rather than just the concept. This is achieved by thinking about its object in a mathematical way. For someone P, it's like getting a formula from the definition ("Any two massive objects ...").

(F=Gm 1m2/d2)

This liberates truth from the changing world. Our grasp of the ultimate knowable order of the universe can be achieved through pure form, that is, through mathematical means. If Plato's explanation is correct (of course, there will be other explanations), he thinks that there is a correct formula not only for horses or gravity, but also for love and beauty.

Today, many of us are willing to admit the former, but refuse to admit the latter. As we all know, the aesthetic tastes of different individuals and cultures are relative, which we think can refute Plato. Parisians and Ubangians have different views on what beauty is. But in Plato's view, if Paris fashion models and Princess Ubangi are really beautiful, then there must be "beauty". Perhaps it has something to do with dealing with "order" in a mathematical way, which includes elegance, harmony and lust. Perhaps one day Sir Newton in the field of aesthetics will appear and complete this equation: "Beauty = ..."

Finally, about Plato, we also want to discuss the part of his theory related to learning. MINO is a dialogue about this process. In the book, MINO and Socrates discuss "virtue" and whether virtue can be taught. Socrates forced MINO to admit that he didn't know what virtue was, so MINO didn't know whether virtue could be taught. (In other words, Socrates has brought the dialogue to the end of the "second stage" mentioned in the first chapter. ) Socrates and MINO both admitted their ignorance. Socrates said that if MINO is willing, he is willing to continue this topic seriously. At this time, MINO raised a question called MINO Paradox. MINO asked how it is possible to explore knowledge about X, or that a person already has knowledge about X, in which case he doesn't need to explore; Either a person has no knowledge about X, in which case, even if he tries to explore, he won't realize what he is looking for. Socrates seems to regard MINO's question as a joke, but in fact, he is very serious.

MINO and Socrates were walking in the garden when they met a gardener, an uneducated child slave. Socrates asked him to solve the multiplication problem of square area, which is a rather complicated geometric problem. The boy refused to answer, saying that he had never studied mathematics. But Socrates was not discouraged and began to ask a series of questions, such as "Should this question be answered by an arc or a straight line?" (Try using a straight line. ) "Should I add a straight line inside or outside the square?" (First, it's outside. If it fails, it's inside. ) After answering a long list of questions that can be answered with "yes" or "no", the boy finally got the correct answer-as shown in the figure:

So Socrates thinks that a child slave who has never been to school can solve a math problem without you providing him with any information he doesn't have beforehand. We may think that Socrates' method contains some very clever techniques in this case. However, Plato's conclusion is that child slaves already know the answer to the question, but they just don't know that they know it. Plato believes that truth exists in the soul of child slaves. It is unconscious knowledge based on innate ideas. The concept of talent is the idea that an individual soul has at birth. Plato's view may mean that all real knowledge expresses the same principle to varying degrees (A=A). This principle cannot be learned by observation (because it is innate). It must be an innate concept, and it is the innate concept of all of us. However, whether this is the correct explanation of Plato's view is still controversial. In any case, for Plato, all learning is actually memories. We answered the "Minos Paradox" (how do we know what we don't know), saying that in fact we know what we don't know, and learning is memory. Therefore, similar to Freud and Proust (the author of the seven-volume novel Remembrance of Time Past), Plato attached great importance to memory and regarded it as the core feature of his epistemology.

Let's review the core features of Plato's epistemology. To acquire knowledge is to transcend the ever-changing material world and grasp the eternal rational order behind change. This order will prove that the special contains universality. This kind of "grasping" is a rational activity of the mind, and it is purely formal (that is, mathematical) in the form of expression. This kind of rational activity can only be based on a certain concept of talent, and only when the concept of talent exists can rational activity occur. We can finally acquire knowledge by showing how the visible world is related to the eternal order of knowable truth, thus making the visible world knowable. These characteristics of Plato's epistemology are the program of rationalism, which is one of the two opposing camps in the field of western ideological epistemology.

Plato's rationalism was immediately opposed by his student Aristotle, who developed in the direction of what was eventually called empiricism (empiricism will be discussed in chapter 3). Rationalism occupies a dominant position in late Greek philosophy, Roman philosophy and early medieval philosophy. /kloc-St. Thomas Aquinas publicly opposed rationalism for the first time in the 0/3rd century, and he revived Aristotle's theory in his works.