_Leucippus of Miletus_ (B.C. 500-400) appears, in the order of speculation, as the successor of Anaximander. _Atoms_ and _space_ are, in his philosophy, the ἀρχαί, or first principles of all things. "Leucippus (and his companion, Democritus) assert that the plenum and the vacuum [_i.e._, body and space] are the first principles, whereof one is the Ens, the other Non-ens; the differences of the body, which are only figure, order, and position, are the causes of all others."[422] [Footnote 422: Aristotle's "Metaphysics," p. 21 (Bohn's edition).] He also taught that the elements, and the worlds derived from them, are _infinite_. He describes the manner in which the worlds are produced as follows: "Many bodies of various kinds and shapes are borne by amputation from the infinite [_i.e._, the chaotic μῖγμα of Anaximander] into a vast vacuum, and then they, being collected together, produce a vortex; according to which, they, dashing against each other, and whirling about in every direction, are separated in such a way that like attaches itself to like; bodies are thus, without ceasing, united according to the impulse given by the vortex, and in this way the earth was produced."[423] Thus, through a boundless void, atoms infinite in number and endlessly diversified in form are eternally wandering; and, by their aggregation, infinite worlds are successively produced. These atoms are governed in their movements by a dark negation of intelligence, designated "Fate," and all traces of a Supreme Mind disappear in his philosophy. It is a system of pure materialism, which, in fact, is Atheism. [Footnote 423: Diogenes Laertius, "Lives," p. 389.] _Democritus of Abdera_ (B.C. 460-357), the companion of Leucippus, also taught "that _atoms_ and the _vacuum_ were the beginning of the universe."[424] These atoms, he taught, were infinite in number, homogeneous, extended, and possessed of those primary qualities of matter which are necessarily involved in extension in space--as size, figure, situation, divisibility, and mobility. From the combination of these atoms all other existences are produced; fire, air, earth, and water; sun, moon, and stars; plants, animals, and men; the soul itself is an aggregation of round, moving atoms. And "motion, which is the cause of the production of every thing, he calls _necessity_."[425] Atoms are thus the only real existences; these, without any pre-existent mind, or intelligence, were the original of all things. [Footnote 424: Diogenes Laertius, "Lives," p. 395.] [Footnote 425: Id, ib., p. 394.]