Plato stands at the center of philosophical thought in the ancient world. He was the first person to approach philosophical issues systematically, but it was the genius with which he treated those issues that made his thought so influential. Virtually every philosopher who came after Plato in antiquity was responding, either favorably or unfavorably, to what he had written. Moreover, Plato's influence was hardly limited to the ancient world. Plato's thought was studied throughout the Middle Ages and the Renaissance, and continues to be crucial to an understanding of philosophical issues. Although the correctness of his doctrines has always been the subject of vigorous debate, no one can deny the pervasive influence of Plato's thought on the history of Western philosophy.

Plato was born in Athens, the son of Ariston and Perictione (or, in some reports, Potone). According to Diogenes Laertius in his Lives and Opinions of Eminent...