Plato’s Dialectic―A Method of Division

Plato (427-347 BC), a disciple of Socrates, tried to explain how true knowledge, concerning the virtue referred to by Socrates, comes to be obtained. Plato maintained the existence of non-material being, which is the essence of a thing, and he called it Idea, or form (eidos). Among scores of Ideas he regarded the Idea of the Good as supreme, and asserted that only when people intuit the Idea of the Good can they lead the supreme life.

According to Plato, that which truly exists is Idea, and the phenomenal world is but a copy of the world of Ideas. Accordingly, a knowledge of the Ideas is indeed true knowledge. He also called his method, the cognition of Ideas, the dialectic.

Plato’s dialectic sought to determine the relationships between Ideas and to explain the structure of Ideas, which placed the Idea of the Good at the apex. In the cognition of Ideas, there are two directions: The first progresses from the upper to the lower through the division of the generic concepts into specific concepts; the second progresses from the lower to the upper through synthesizing the concepts of individual things, aiming at the supreme concept. Between the two methods, the direction of synthesis corresponds to Socrates’ dialectic; the direction of division is most typically Plato’s. Thus, when we refer to Plato’s dialectic, we usually mean the method by division.

In contrast to Socrates, who held that knowledge could be obtained through a dialogue between persons, Plato proposed his dialectic as a method of classifying concepts, or a method of self-questioning and self-answering, namely, a method of questioning and answering taking place in one’s own mind.