"He told us that Pythodorus had described to him the appearance of Parmenides and Zeno; they came to Athens, he said, at the great Panathenæa; the former was, at the time of his visit, about sixty-five years old, very white with age, but well-favored. Zeno was nearly forty years of age, of a noble figure and fair aspect; and in the days of his youth he was reported to have been beloved of Parmenides. He said that they lodged with Pythodorus in the Ceramicus, outside the wall, whither Socrates and others came to see them; they wanted to hear some writings of Zeno, which had been brought to Athens by them for the first time. He said that Socrates was then very young, and that Zeno read them to him in the absence of Parmenides, and had nearly finished when Pythodorus entered, and with him Parmenides and Aristoteles, who was afterwards one of the Thirty; there was not much more to hear, and Pythodorus had heard Zeno repeat them before." The _Theætetus_ contains another allusion to Parmenides, which proves in what reverence the old philosopher was held by Socrates: "My reason is that I have a kind of reverence, not so much for Melissus and the others, who say that 'all is one and at rest,' as for the great leader himself, Parmenides, venerable and awful, as in Homeric language he may be called--him I should be ashamed to approach in a spirit unworthy of him. I met him when he was an old man and I was a mere youth, and he appeared to me to have a glorious depth of mind. And I am afraid that we may not understand his language, and may fall short even more of his meaning." Finally, in the _Sophistes_ a passing allusion to the same event is put into the mouth of Socrates: "I remember hearing Parmenides use the latter of the two methods, when I was a young man and he was far advanced in years, in a very noble discussion." These notices of the Eleatic sage, we feel, are not in any sense accidental. Plato has introduced them in important moments of his three most studied dialogues upon those very points which occupied the mind of Parmenides, and by the elaboration of which he made his greatest contribution to philosophy. The problems of knowledge and of the relation of the phenomenal universe to real existence were for the first time methodically treated in the school of Elea. Their solution in the theory of Ideas was the main object of Plato's philosophical activity.