III. LEUCIPPUS AND DEMOCRITUS.--Leucippus is variously called a native of Elea, of Abdera, of Melos, of Miletus. He was a pupil of Zeno the Eleatic. [144] Democritus was a native of Abdera. They seem to have been almost contemporary with Socrates. The two are associated as thorough-going teachers of the 'Atomic Philosophy,' but Democritus, 'the laughing philosopher,' as he was popularly called in later times, in distinction from Heraclitus, 'the weeping philosopher,' was much the more famous. [145] He lived to a great age. He himself refers to his travels and studies thus: "Above all the men of my time I travelled farthest, and extended my inquiries to places the most distant. I visited the most varied climates and countries, heard the largest number of learned men, nor has any one surpassed me in the gathering together of writings and their interpretation, no, not even the most learned of the Egyptians, with whom I spent five years." We {75} are also informed that, through desire of learning, he visited Babylon and Chaldaea, to visit the astrologers and the priests. [146] Democritus was not less prolific as a writer than he was voracious as a student, and in him first the division of philosophy into certain great sections, such as physical, mathematical, ethical, was clearly [147] drawn. We are, however, mainly concerned with his teaching in its more strictly philosophical aspects. His main doctrine was professedly antithetical to that of the Eleatics, who, it will be remembered, worked out on abstract lines a theory of one indivisible, eternal, immovable Being. Democritus, on the contrary, declared for two co-equal elements, the Full and the Empty, or Being and Nonentity. The latter, he maintained, was as real as the former. As we should put it, Body is unthinkable except by reference to space which that body does not occupy, as well as to space which it does occupy; and conversely Space is unthinkable except by reference to body actually or potentially filling or defining it. What Democritus hoped to get by this double or correlative system was a means of accounting for or conceiving of _change_ in nature. The difficulty with the Eleatics was, as we have seen, how to understand whence or why the transition from that which absolutely is, to this strange, at least apparent, system of eternal flux and transformation. Democritus {76} hoped to get over this difficulty by starting as fully with that which _is not_, in other words, with that which _wants_ change in order to have any recognisable being at all, as with that which _is_, and which therefore might be conceived as seeking and requiring only to be what it is. [148]