Plato's theory of ideas
Plato's philosophy is based on the distinction between reality and appearance. This was influenced somewhat by Parmenides, and the religious tone of reality is Pythagorean. This gave rise to a doctrine that felt satisfied both intellectual needs and religious feelings. The result is a very powerful synthesis that has influenced many great philosophers, including Hegel, in different forms.
Plato thought of the philosopher as a man who loved to "see the truth." Philosophers love beauty itself. Those who love good things have only opinion, while those who know absolute beauty have knowledge.
The difference between knowledge and insights. Knowledge is the knowledge of something that exists, because what does not exist is not something. In this way, knowledge cannot go wrong. And insights can be mistaken, and opinions are about things that exist and don't exist. This seems impossible. But Plato believed that certain things always share a pair of opposite properties: things as beautiful are ugly in some ways. All specific sensations have this contradictory nature, so they are thus somewhere between being and not existing. Thus an important conclusion is drawn: insight is about the world that is presented before the senses, and knowledge is about an eternal world beyond the senses.
Plato's theory of "ideas" is partly logical and partly metaphysical. The logical part means that the nature of things cannot be located in time and space, it is "eternal". The metaphysical part, on the other hand, means that everything has its own "idea" or "form" that exists in the ideal.
Plato believed that philosophy is an insight, an insight into "truth." It is not purely intellectual, because it is not only wisdom, but also love of wisdom. However, practice has shown that what looks like a sudden insight can be misleading, so it needs to be soberly and carefully examined. But Plato was fully convinced of his insight. He distinguished between the world of reason and the world of feeling. Reason and sensation are divided into two separate categories. Reason is divided into "reason" and "understanding." Reason is a higher level of reason, involving pure ideas, and its methods are dialectical. Enlightenment is the kind of intellectual method used in mathematics.
Plato made his understanding of the nature of insight his famous cave metaphor, which later generations called the "cave" theory. He said that a person who lacks philosophy is like a prisoner in a cave. They are shackled and can only look in one direction. Behind them was a pile of fires and a wall in front of them. There was nothing between them and the wall. All they see is the shadow of themselves and the objects behind them. Inevitably, they see these shadows as real things and know nothing about what causes them. Finally a man managed to escape from the cave, he came to the sun, saw for the first time something real, and realized that he had been blinded by the shadow before. If this man is the philosopher who is fit to be a guardian, it is his duty to go back to the cave, to teach the cave people the truth, and to show them the way out. But it would be very difficult for the man who had escaped to persuade the prisoner. Because coming back into the cave from the sun, he sees the shadow more clearly than his companions do, which makes his companions think he is stupid than he was before he escaped! (I think Plato's theory is very relevant, and people often arbitrarily deny things that are different from habits or from what they see and hear, and the actual situation is often that their subjective feelings are wrong.) This requires us to think critically about some issues. ）
The place of "goodness" in Plato's philosophy is extraordinary. He said that both science and truth are close to the good, but the good has a higher status. "Goodness is not the essence, and it is far greater than the essence in dignity and strength. To be the opposite of phenomena is to be perfectly good, so to know reality is to know goodness. From this point of view, Plato's philosophy, like Pythagoreanism, also runs through the fusion of reason and mysticism, but in the end, mysticism clearly prevails.
Plato was the first to propose the theory of universality, although he could not argue enough about it in many ways. He is completely unaware of the great gap between universality and speciality, and that his "ideas" are nothing more than moral and aesthetic superiority over ordinary kinds.
Plato's theory of ideas also had a profound impact on science, thus providing an example of a universal truth: that a hypothesis, however absurd, could be useful to science, as long as it allowed the explorer to conceive of things in a new way. But when the hypothesis has been fortunate enough to play this role, it has the potential to become an obstacle to the progress of science. Faith in the good is useful as a key to scientific understanding of the world—at some stage, in astronomy—but at any later stage it is harmful. Plato's, more so, Aristotle's ethical and aesthetic prejudices were once greatly stifling Greek science.