He is said to owe much to Protagoras, and wrote a dialogue under that title. In politics, as in morals, he drew largely from the opinions of his master, Socrates; and it is related that he was indebted to the books of Sophron, which, having been long neglected, were by him first brought to Athens, and found under his pillow at his death. Certainly he, of all scholars, had the best right to borrow, since none could recognize his own in his pages, and any author might glory in being esteemed worthy of lending a syllable to so consummate a creator. On returning to Athens from his Egyptian travels, he settled himself in the Academy, a gymnasium, or place of exercise, in the suburbs of the city, surrounded by woods, and taking its name from Academus, one of the heroes. "The fluent, sweet-tongued sage first led the way, Who writes as smoothly as from some green spray Of Academe grasshoppers chirp their lay." The occasion of his living here was that he owned an orchard adjoining the Academy. In process of time, this orchard was much enlarged by good-will, studious persons bequeathing of their riches to the professors of philosophy, to maintain the quiet and tranquillity of a philosophical life. Here he first taught philosophy; afterwards in the Gardens of Colonus. At the entrance of his school was written,-- "Let none ignorant of geometry enter here"; signifying, by this inscription, not only the proportion and harmony of lines, but also of inward affections and ideas. His school took the name of the Academy. He thought it was a great matter, in the education of youth, to accustom them to take delight in good things; otherwise, he affirmed, pleasures were the bait of evil. Education should be conducted with a serene sweetness, never by force or violence, but by gentleness, accompanied with persuasion and every kind of invitation. His teaching was conducted by conversation or dialogue. His method of discourse was threefold,--first, to declare what that is which is taught; then, for what reason it is asserted, whether as a principal cause, or as a comparison, and whether to defend the tenet, or controvert it; thirdly, whether it be rightly said. He expounded the things which he conceived to be true; confuted those which were false; suspended his opinions on those which were doubtful. His philosophy comprised the elements of the school of Heraclitus, Pythagoras, and Socrates, combined in a system which he distributed into three parts,--moral, consisting of action; natural, in contemplation; rational, in distinction of true and false, which, though useful in all, yet belongs to pure thought. As of old, in a tragedy the chorus acted alone; then Thespis, making some intermissions of the chorus, introduced one actor, Æschylus a second, Sophocles a third; in like manner, philosophy was at first but of one kind,--physic; then Socrates added ethic; thirdly, Plato, inventing dialectic, made it perfect.