Plato regards education as a means to achieve justice, both individual justice and social justice. According to Plato, individual justice can be obtained when each individual develops his or her ability to the fullest. In this sense, justice means excellence. For the Greeks and Plato, excellence is virtue. According to Socrates, virtue is knowledge. Thus, knowledge is required to be just. From this Plato concludes that virtue can be obtained through three stages of development of knowledge: knowledge of one's own job, self-knowledge, and knowledge of the Idea of the Good. According to Plato, social justice can be achieved when all social classes in a society, workers, warriors, and rulers are in a harmonious relationship. Plato believes that all people can easily exist in harmony when society gives them equal educational opportunity from an early age to compete fairly with each other. Without equal educational opportunity, an unjust society appears since the political system is run by unqualified people; timocracy, oligarchy, defective democracy, or tyranny will result. Modern education in Japan and other East Asian countries has greatly contributed to developing their societies in economic terms. Nevertheless, education in those countries has its own problems. In particular the college entrance examination in Japan, Korea, and other East Asian countries caused serious social injustices and problems: unequal educational opportunity, lack of character education, financial burden on parents, and so on. Thus, to achieve justice, modern society needs the Platonic theory education, for Plato's philosophy of education will provide a comprehensive vision to solve those problems in education. There is also some controversy about the relationship between education and economics. It is a popular view common in East and West that businesses should indirectly control or even take over education to economically compete with other nations. However, Plato disagrees with this notion since business is concerned mainly with profit whereas a true education is concerned with the common good based upon the rational principle of individual and social justice.