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: ][ (return) ] 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: ][ (return) ] 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: ][ (return) ] Diogenes Laertius, "Lives," p. 395.
[Footnote 425: ][ (return) ] Id, ib., p. 394.
The psychological opinions of Democritus were as decidedly materialistic as his physical theories. All knowledge is derived from sensation. It is only by material impact that we can know the external world, and every sense is, in reality, a kind of touch. Material images are being continually thrown off from the surface of external objects which come into actual contact with the organs of sense. The primary qualities of matter, that is, those which are involved in extension in space, are the only objects of real knowledge; the secondary qualities of matter, as softness, hardness, sweetness, bitterness, and the like, are but modifications of the human sensibilities. "The sweet exists only in form--the bitter in form, hot in form, color in form; but in causal reality only atoms and space exist. The sensible things which are supposed by opinion to exist have no real existence, but atoms and space alone exist." [426]
[Footnote 426: ][ (return) ] Lewes's "Biographical History of Philosophy," p. 96. The words of Democritus, as reported by Sextus Empiricus.
Thus by Democritus was laid the basis of a system of absolute materialism, which was elaborated and completed by Epicurus, and has been transmitted to our times. It has undergone some slight modifications, adapting it to the progress of physical science; but it is to-day substantially the theory of Democritus. In Democritus we have the culmination of the mechanical theory of the Ionian or Physical school. In physics and psychology it terminated in pure materialism. In theology it ends in positive Atheism.