Plato's Utopia is the earliest Utopia in human history. In his ideal country, the ruler must be a philosopher. He thinks all the existing politics are bad. The real way out for mankind lies in the philosophers who hold political power, and only real philosophers can save the crisis of the polis at that time. This belief constitutes the core of Plato's mature political philosophy system. In his eyes, "philosopher" has a special connotation. He believes that philosophers are the noblest and most knowledgeable people, and this sage regime under the rule of saints is the best regime. Therefore, only the establishment of a country with philosophers as the king is the most ideal country. This country is a model country that exists in the sky. In his view, the essence of philosophers is knowledge, wisdom, justice and kindness. Only philosophers can understand the highest idea of a country, that is, the grasp of "goodness", while others can only grasp "opinions" As a science, governing the country can only be mastered by philosophers, and only philosophers can be qualified to be in power. That is to say, only philosophers can reach an understanding of the concept of the state and know how the "ideal country" should be organized and governed. In this way, the so-called ruler is understood by Plato as a combination of superb wisdom, true knowledge, perfect virtue and absolute supreme power. He firmly believes that only philosophers can save the city-state and the people, and philosophers are the inevitable rulers of the ideal country. Justice and goodness pursued by human beings is the theme of Plato's Republic. He believes that it is meaningful for the country, politics and law to face the real existence and be related to the human soul. In the Republic, Socrates just started to discuss the topic of "justice", from which we can see how strong Plato's desire for justice is! He believes that absolute justice lies in God, which just confirms the declaration at the end of the dialogue, "Let's always be on the right path and pursue justice and wisdom". Justice and wisdom are not only the theme of the country, but also the essence of the whole universe, because the starting point of the country is "endless time and changes brought about by time." Plato's justice is temperance in love. In the eyes of many of us, Platonic love seems to be synonymous with spiritual love, which refers to the kind of love that transcends time and space and exists only between souls and does not occupy each other's bodies. In fact, the true meaning of Platonic love refers to a kind of advocating the golden mean and pursuing goodness and beauty.