Plato's philosophical ideas are more content, and the author will tell them in two articles, and the author has proposed subheadings for each content to be easier to read.
Philosophy
To understand Plato's philosophical thought, we must first have an understanding of his theory of ideas. We generally think that ideas exist in the human brain, people always see things in the objective world first, and then abstract the ideas of things in the mind, so ideas are subjective. And Plato believes that ideas are both objective and subjective, and the objective point is that ideas first exist independently in the world of ideas, and people have ideas in the human brain, and people create things according to the ideas in the brain, so the ideas in the human brain are subjective. For example, if a carpenter creates a table, first the idea of "table" exists independently in the world of ideas, and then the carpenter has the idea of "table" in his mind, and then creates a variety of tables that we can see according to this concept.
Plato also divided the world of ideas into six layers, such as the form of pyramids, from the bottom up: 1. the concept of natural objects, such as flowers, grass, trees; 2. the concept of man-made things, such as tables and chairs; 3. the concept of numbers, such as square, round, greater than, less than; 4. the concept of philosophical categories, such as existence and non-existence, motion and static; 5. the concept of moral aesthetics, such as justice, bravery, wisdom; 6. The highest idea, "goodness.". In addition to the world of ideas, Plato believed that there was also a world of sensations, the world we usually see. The world of sensation is an imitation and division of the world of ideas, which exists and does not exist. It exists because it has the form of the world of ideas, and does not exist because the materials that make it up come from primitive matter. Primordial matter is a chaos, non-existence. The world of ideas, the world of sensations, and the primitive matter make up the three-level world of Plato's idea. The tertiary world has the following characteristics: first, individual things tend to be their prototypes; second, low-level ideas tend to higher ideas; and third, all ideas tend to the highest idea, "goodness.". Interestingly, in contrast to Democritus's "atomic theory", we can find that plato's original matter (non-existence) is exactly Democritus's atom—existence.
Creationism
Plato's theory of ideas can explain the formation of man-made things, but it is impossible to find the "maker" in natural things. Being able to follow the concept of natural objects to create the natural world, this craftsman cannot be a man, but only a god. Naturally derived from Plato's creationism, Demug (God) processes the already existing primordial matter (material) into nature according to the idea of natural things in the mind. In contrast to the Christian creationism of God, what they all have in common is that there is a supernatural God who creates the natural world according to the ideas in the mind. The difference is that Demug did not create materials, but only craftsmen; while God, without any material, spoke from his mouth and created the natural world out of nothing.
Segment theory
Plato's epistemology is consistent with his theory of ideas (ontology), and he uses the "line segment theory" to illustrate the correspondence between his epistemology and ontology. There are three epistemological phases corresponding to the world of primitive matter, sensation, and ideas: ignorance, opinion, and truth. Primitive matter corresponds to ignorance, representing a chaos, a chaotic nightmare. The sensory world that rises to ontology corresponds to opinions, which can be divided into two paragraphs: imagination and belief, which are the perceptual understanding of specific things in the sensory world, and imagination is only the understanding of the shadow of things. Obviously, imagination is one level lower than belief. Further up and corresponding to the world of ideas is the truth, truth can also be divided into two paragraphs, reason refers to the knowledge of ideas such as mathematical theory, which needs to be perceived through sensory stimulation, and reason is the purest abstract philosophical category of cognition, which does not need to be known by the senses, such as existence, beauty, etc. Obviously, rationality is one level higher than reason. All opinions and truths are collectively called knowledge, as opposed to ignorance.
Cave theory
Plato used the "cave theory" as an example of the process by which man knows the truth. Suppose there is a group of people who have been tied up in a cave since childhood, and behind them are puppets of various images (people, cats, dogs, etc.), back and forth, and then there are torches reflecting the puppets, these people are fixed and cannot turn around, they can only see the shadows of the puppets on the wall in front of them, so they think that the world is made up of these shadows. If one of them is untied, stands up, and turns around, they will find that the shadow is not a fact of the world, but a puppet. When he came out of the cave and saw the flowers and plants of the outside world, he realized that the puppets in the cave were only imitations of the things in the outside world, and when he looked up at the sun again, he finally realized that the sun was the reason why everything could be seen. We correspond the things mentioned in the cave theory to Plato's ontological and epistemological concepts: the puppet — the world of sensations, beliefs, people and things outside — the world of ideas, reason or reason, the sun — the ultimate good, and of course the shadow of the first puppet seen is the shadow of sensation, corresponding only to the imagination of the world of sensation. (To be continued)
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Key references for this series:
Course on the History of Western Philosophy by Lin Zhao and Xiaomang Deng;
samuel enoch stumpf, james fieser, History of Western Philosophy;
Selected excerpts from Plato's dialogues: Euthyphro, Apologetics, Kerry, Philo, etc.;
Others are constantly growing...