_Parmenides_ was a native of Elea or Velia, and flourished about 460 B.C., soon after which time he came to Athens, and became acquainted with Socrates, who was then very young. Theophrastus and Aristotle speak doubtfully of his having been a pupil of Xenophanes. Some authors, however, reckon him as one of the Pythagorean school; Plato and Aristotle speak of him as the greatest of the Eleatics; and it is said that his fellow-countrymen bound their magistrates every year to abide by the laws which he had laid down. He, like Xenophanes, explained his philosophical tenets in a didactic poem, in which he speaks of two primary forms, one the fine uniform etherial fire of flame (φλόγος πῦρ), the other the cold body of night, out of the intermingling of which everything in the world is formed by the Deity who reigns in the midst. His cosmogony was carried into minute detail, of which we possess only a few obscure fragments; he somewhat resembled the Pythagoreans in believing in a spherical system of the world, surrounded by a circle of pure light; in the centre of which was the earth; and between the earth and the light was the circle of the Milky Way, of the morning and evening star, of the sun, the planets, and the moon. And the differences in perfection of organization, he attributed to the different proportions in which the primary principles were intermingled. The ultimate principle of the world was, in his view, necessity, in which Empedocles appears to have followed him; he seems to have been the only philosopher who recognised with distinctness and precision that the Existent, τὸ ὄν, as such, is unconnected with all separation or juxtaposition, as well as with all succession, all relation to space or time, all coming into existence, and all change. It is, however, a mistake to suppose that he recognised it as a Deity. _Democritus_ was born at Abdera, B.C. 460. His father Hegesistratus had been so rich as to be able to entertain Xerxes, when on his march against Greece. He spent his inheritance in travelling into distant countries, visiting the greater part of Asia, and, according to some authors, extending his travels as far as India and Æthiopia. Egypt he certainly was acquainted with. He lived to beyond the age of 100 years, and is said to have died B.C. 357.