_Plato_, the greatest of all the disciples of Socrates, was the son of Ariston and Perictione, and was born probably in the year B.C. 428, and descended, on the side of his father, from Codrus, and on his mother’s side related to Solon. At the age of twenty, he became a constant attendant of Socrates, and lived at Athens till his death. After this event, in consequence of the unpopularity of the very name of his master, he retired to Megara, and subsequently to Sicily. He is said also to have been at some part of his life, after the death of Socrates, a great traveller. About twelve years after the death of Socrates he returned to Athens, and began to teach in the Academy, partly by dialogue, and partly, probably, by connected lectures. He taught gratuitously; and besides Speusippus, Xenocrates, Aristotle, Heraclides Ponticus, and others, who were devoted solely to philosophical studies, he is said to have occasionally numbered Chabrias, Iphicrates, Timotheus, Phocion, Isocrates, and (by some) Demosthenes among his hearers. He died at a great age, B.C. 347. His works have come down to us in a more complete form than those of any other ancient author who was equally voluminous; and from them we get a clear idea of the principal doctrines which he inculcated on his followers. Like Socrates, he was penetrated with the idea, that knowledge and wisdom were the things most necessary to man, and the greatest goods assigned to him by God. Wisdom he looked on as the great purifier of the soul; and as any approach to wisdom presupposes an original communion with _Being_, properly so called, this communion also presupposes the divine nature, and consequent immortality of the soul, his doctrine respecting which was of a much purer and loftier character than the usual theology of the ancients. Believing that the world also had a soul, he considered the human soul as similar to it in nature, and free from all liability to death, in spite of its being bound up with the appetites, in consequence of its connexion with the body, and as preserving power and consciousness after its separation from the body. What he believed, however, to be its condition after death is far less certain, as his ideas on this subject are expressed in a mythical form.