Born at Athens in a family of noble descent, Plato (b. c. 428–427– d. c. 348–347 bce) naturally sought throughout his life to play a political role as councilor or legislator, not only at Athens but also abroad, especially in Sicily. A writer and philosopher, Plato was above all a citizen who, as is attested by the ten books of the Republic and the twelve books of the Laws (which constitute almost half of his work), wished to reform the political life of his city by assigning power not to wealth or to military force, but to knowledge. Against the traditional vision of culture in his time, essentially transmitted by poetry, Plato proposed a new system of education based on knowledge, in which mathematics plays an important role, and which culminates in the contemplation of true realities and of the Good. Plato’s life is therefore inseparable from his thought. Fairly early, a dogmatism (the term being taken in the minimal sense of the exposition of a doctrine) developed, with the appearance of a doctrine whose principal points became more specific over time. This doctrine is characterized by a twofold reversal. First, the world of things perceived by the senses is a mere image of a set of intelligible forms that represent true reality, for they possess the principle of their existence within themselves. Second, human beings cannot be reduced to their bodies, for their true identity coincides instead with an incorporeal entity, the soul, that accounts for all motion, both material (growth, locomotion, etc.) and spiritual (feelings, sense perceptions, intellectual knowledge, and so on).