Plato is the founder of western objective idealism, and his philosophical system is extensive and profound, which has a great influence on his teaching thought.

Plato pointed out that the world consists of "the world of ideas" and "the world of phenomena". The conceptual world is real and eternal, and the real world that human senses come into contact with is only a faint shadow of the conceptual world, which is composed of phenomena, and each phenomenon presents temporary changes due to factors such as time and space.

Based on this, Plato put forward the epistemology of idealism and memory as the philosophical basis of his teaching theory.

In order to be universal, any philosophy must include theories about nature and the universe. Plato tried to grasp the eternal truth about the individual and nature, so he developed a natural philosophy that was suitable for and subject to his political and theological views.

Tangible things in nature are fluid, but the forms or ideas that make up these tangible things are eternal. Plato pointed out that when we say "horse", we don't mean any horse, but any kind of horse.

The meaning of "horse" itself is independent of all kinds of horses ("tangible"). It does not exist in time and space, so it is eternal. But a concrete and tangible horse that exists in the sensory world is "moving", will die and rot. This can be used as a preliminary explanation of Plato's theory of ideas.

We can't really understand those things that change and flow. We only have opinions or opinions about them. The only thing we can really understand is the form or concept that we can understand rationally. Therefore, knowledge is fixed and certain, and there can be no wrong knowledge. But the view may be wrong.

In Plato's Republic, there is a famous cave metaphor to explain idealism: a group of prisoners are in a cave, their hands and feet tied, and their bodies can't turn, so they can only turn their backs to the hole.

There is a white wall in front of them and a fire burning behind them. On that white wall, they saw their own shadow and something between them and the fire. Because they can't see anything else, prisoners will think that shadows are real things.

Finally, a man broke free from the shackles and groped his way out of the hole. He saw the real thing for the first time. He went back to the cave, trying to explain to others that those shadows are just illusory things and show them the bright way. But for those prisoners, this man seems to be more stupid than before he escaped, declaring to him that there is nothing in this world except the shadow on the wall.

Plato used this story to tell us that "form" is actually something real in the sun, and all our sensory world can feel is the shadow on the white wall. Compared with the bright rational world, our nature is dark and monotonous. People who don't understand philosophy can only see those shadows, and philosophers see external things in the sunshine of truth.

On the other hand, Plato compared the sun to justice and truth, emphasizing that the sunshine we see is only the form of the sun, not the essence; Just like true philosophical truth and justice, they can only be seen in their external manifestations, but their essence is unspeakable.

Plato's Republic also depicts an ideal utopia for us. Plato believed that countries should be ruled by philosophers. Citizens in Plato's Republic are divided into three categories: patriots, soldiers and ordinary people. The defenders of the country are a few elites who manage the country.

It can be inherited, but outstanding children of other classes can also be cultivated into patriots, and the descendants of patriots may also be reduced to the ordinary class. The task of defending the country is to supervise the formulation and implementation of the code. Plato has a complete set of theories to achieve this goal.

His utopia requires everyone to have his special function in society to meet the overall needs of society. But in this country, women and men have the same rights, and men and women are completely equal. When it is in the public interest, the government can lie. Everyone should do his own thing and should not disturb others.

Today, Plato's utopia is a terrible totalitarian country. But "the ideal country is actually the view of scientists who manage the country in the right way", Plato himself did not try to realize the state machine in the ideal country.

Plato pointed out in the Law that a "constitutional state" is the best country after an ideal country. He also pointed out in the book that women and men should receive the same respect and training.

Plato tried to make astronomy a branch of mathematics. He believes: "Astronomy, like geometry, can be studied by asking questions and solving problems, regardless of celestial boundaries."

Plato believes that the origin of the universe is an indistinguishable chaos (the universe itself is always chaotic in Plato's view). This chaotic development is the result of the activities of supernatural gods.

Plato believes that the most important feature of the universe from chaos to order is that the creator has made a rational plan for the world; The mechanical process of putting this scheme into practice is a natural event.

Plato's cosmology is basically a mathematical cosmology. He imagined that there were two kinds of right-angled triangles at the beginning of the universe, one was half of a square and the other was half of an equilateral triangle. From these triangles, four kinds of regular polyhedrons are reasonably produced, which constitute particles of four elements.

Fire particles are regular tetrahedrons, gas particles are regular octahedrons, water particles are regular icosahedrons, and soil particles are cubes. The fifth regular polyhedron is a dodecahedron formed by a regular pentagon, and it is the fifth element that constitutes the matter in the sky, called ether. The whole universe is a sphere, because the sphere is symmetrical and perfect, and any point on the sphere is the same.

The universe is also alive and moving, and a soul fills all the spaces. The motion of the universe is circular, because circular motion is the most perfect and does not need hands or feet to push it. The quantities of the four elements in the universe are as follows: the ratio of fire to gas is equal to the ratio of gas to water, and the ratio of water to soil. Everything can be named by a number, which is the proportion of the elements they contain.

Extended data:

I. Introduction

Plato (ancient Greek: π λ? ▽ν, transliteration: Plá t ν n, international phonetic symbol: [plátūn], about 429- 347 BC) was a famous ancient Greek philosopher and an Athenian. Most of his works are recorded in the form of dialogues, and he founded a famous college.

Plato was a student of Socrates and a teacher of Aristotle. They are generally regarded as the founders of western philosophy, and are called "the three sages of the West" or "the three philosophers of Greece" in history.

Second, Plato's "ideal world"

Plato's ideal world theory points out that the real world we feel only reflects the shadow of a higher level world. Plato believes that there is the most ideal reason in this higher world, and this form realizes real light, not just shadow.

The sweetness of the food we taste is only the shadow reflected by the principle of "sweetness", and the radiant sun we see is only the afterimage reflected by "light" itself.

"Li" should be regarded as eternal things, that is, they are eternal, perfect and static. Because they are perfect models, they have no reason to be changed or evolved. According to this logic and Plato's theory, we can imagine that there is a higher state of perfection in the universe, in which any form is ultimate or perfect.

All forms are assigned to a part of the perfect state, and all forms reflect a part of truth in the real world.

Third, the theory of knowledge

Plato's exposition of the nature of knowledge and learning in Mino is also influential. He discussed whether virtue can be taught and what virtue is, and expounded how to discover existing knowledge through memory and learning. At the same time, he also discussed how to explain those views that are correct without clear evidence.

Plato believes that knowledge is innate, so learning is only to excavate the ideals originally buried in the depths of the soul, and this excavation process is often guided by philosophers. Plato believes that every soul is born with a "perfect form" and perfect knowledge of everything, so when they study, they just "recall" this knowledge.

Plato believes that we can't really understand those changing and flowing things. We only have opinions or opinions about them. The only thing we can really understand is the "form" or "concept" that we can understand with reason. So Plato thinks that knowledge is fixed and certain, and there can be no wrong knowledge. But the view may be wrong.

References:

Baidu encyclopedia-Plato