Democritus (c.460–c.370 B.C.), Greek pre- Socratic philosopher. He was born at Abdera, in Thrace. Building on Leucippus and his atomism, he developed the atomic theory in The Little World-system and numerous other writings. In response to the Eleatics’ argument that the impossibility of not-being entailed that there is no change, the atomists posited the existence of a plurality of tiny indivisible beings – the atoms – and not-being – the void, or empty space. Atoms do not come into being or perish, but they do move in the void, making possible the existence of a world, and indeed of many worlds. For the void is infinite in extent, and filled with an infinite number of atoms that move and collide with one another. Under the right conditions a concentration of atoms can begin a vortex motion that draws in other atoms and forms a spherical heaven enclosing a world. In our world there is a flat earth surrounded by heavenly bodies carried by a vortex motion. Other worlds like ours are born, flourish, and die, but their astronomical configurations may be different from ours and they need not have living creatures in them. The atoms are solid bodies with countless shapes and sizes, apparently having weight or mass, and capable of motion. All other properties are in some way derivative of these basic properties. The cosmic vortex motion causes a sifting that tends to separate similar atoms as the sea arranges pebbles on the shore. For instance heavier atoms sink to the center of the vortex, and lighter atoms such as those of fire rise upward. Compound bodies can grow by the aggregations of atoms that become entangled with one another. Living things, including humans, originally emerged out of slime. Life is caused by fine, spherical soul atoms, and living things die when these atoms are lost. Human culture gradually evolved through chance discoveries and imitations of nature. Because the atoms are invisible and the only real properties are properties of atoms, we cannot have direct knowledge of anything. Tastes, temperatures, and colors we know only ‘by convention.’ In general the senses cannot give us anything but ‘bastard’ knowledge; but there is a ‘legitimate’ knowledge based on reason, which takes over where the senses leave off – presumably demonstrating that there are atoms that the senses cannot testify of. Democritus offers a causal theory of perception – sometimes called the theory of effluxes – accounting for tastes in terms of certain shapes of atoms and for sight in terms of ‘effluences’ or moving films of atoms that impinge on the eye.
Drawing on both atomic theory and conventional wisdom, Democritus develops an ethics of moderation. The aim of life is equanimity (euthumiê), a state of balance achieved by moderation and proportionate pleasures. Envy and ambition are incompatible with the good life.
Although Democritus was one of the most prolific writers of antiquity, his works were all lost. Yet we can still identify his atomic theory as the most fully worked out of pre-Socratic philosophies. His theory of matter influenced Plato’s Timaeus, and his naturalist anthropology became the prototype for liberal social theories. Democritus had no immediate successors, but a century later Epicurus transformed his ethics into a philosophy of consolation founded on atomism. Epicureanism thus became the vehicle through which atomic theory was transmitted to the early modern period.
See also PRE-SOCRATICS. D.W.G.