Democritus

c. 460-c. 370 B.C.

Greek Philosopher

Democritus embraced the atomism of Leucippus and worked out its detailed application. His atomic theory was the basis for Epicurean philosophy and all later ancient materialistic schools of thought.

Democritus was born at Abdera, in Thrace, although the exact date is unknown. One chronology maintains he was born soon after500 B.C. and died about 404 B.C., while another places his birth around 460 B.C. Tradition has it that he lived to great age; so, if the latter chronology is correct, he lived well into the fourth century B.C. In Little World-system he described himself as a young man when Anaxagoras (c. 500-c. 428 B.C.) was old. This lends support to the latter chronology, which is widely accepted by modern scholars.

Confucius. (Bettmann/Corbis. Reproduced with permission.)

Apparently wealthy, Democritus traveled to Egypt, Chaldea, and the Red Sea. His literary efforts extended over a considerable period and generated over 60 works, including treatises on astronomy, mathematics, music, physics, biology, medicine, and ethics. Known as the "laughing philosopher"—because of his amusement with the follies of man—he left many students. One of these, Nausiphanes, introduced Epicurus (c. 341-270 B.C.) to Democritean atomism.

The only known teacher of Democritus was Leucippus (fl. c. 450-420 B.C.), from whom he learned the essentials of atomism. Leucippus formulated his atomic theory to escape certain difficulties associated with Parmenidean metaphysics. According to Parmenides (b. c. 515 B.C.), nothing can come into being from that which is not, and anything that exists cannot be altered. However, earlier thinkers had argued that all things were derived from a single primary substance: Thales (c. 625-c. 547 B.C.) believed it was water, Anaximander (c. 610-c. 547 B.C.) the Apieron, Anaximenes (fl. 545 B.C.) air, and Heraclitus (fl. 500 B.C.) fire. Unfortunately, each of these theories required an alteration of the primary element.

To avoid this difficulty, Leucippus postulated the existence of an infinite number of unalterable atoms whose combinations give rise to the sensible properties of bodies. Furthermore, he agreed with Parmenides that without a void, motion was impossible. Nevertheless, Leucippus accepted the existence of empty space, since it was that which separated and through which atoms moved. The ideas of Leucippus were highly speculative. Democritus must be given credit for their detailed development.

The atoms of Democritus's system were solid corporeal bodies, both infinite in number and shape as well as of different sizes (though not so big as to be visible). They were devoid of any perceptible qualities and scattered throughout the void, through which they moved perpetually according to unalterable laws of nature. Democritean atoms were certainly extended in space, but they were physically indivisible and otherwise indestructible. Whether or not he thought they were conceptually divisible remains a matter of dispute.

Democritus undertook a detailed exposition of the relationship between specific atomic configurations and the sensible qualities they give rise to. Atomic motions generate collisions that either result in their deflection or adhesion. When hooked or barbed atoms collide, they adhere to one another, forming compound bodies. The various qualities a body possesses, such as color, taste, and temperature, are the consequence of the total number present, their particular arrangement, and the different shapes of the individual atoms. For example, an object's weight varies according to the number of atoms and amount of void contained therein. Additionally, all change was conceived of as a result of atomic combinations, recombinations, and dissociations.

Democritus also taught that all bodies emit thin films of atoms that interact with the organs of sense perception to generate our sensation of objects. Likewise, he taught that thought was the result of interactions with the atoms of the soul. Democritus advocated critical reflection on the evidence of the senses as the best means of obtaining truth.