Democritus (of Abdera) [demokrituhs] (c.470–c.400 bc).
Greek philosopher: pioneer of atomic theory.
Almost nothing is firmly known of Democritus’s life, and his ideas have survived through the writings of others, either supporting or attacking him. His idea of atoms seems to have begun with his teacher Leucippus (5th-c bc), but Democritus much extended the theory. He proposed that the universe contains only a vacuum and atoms, and that these atoms are invisibly small and hard, eternal and are in ceaseless motion. On this adaptable, materialist view he explained taste, smell, sound, fire and death. He supposed that in their form and behaviour lay the natural, godless cause of all things and all events. Plato and Aristotle were not in favour of these ideas, which never formed a part of the mainstream of Greek philosophy, but they were adopted by the Greek philosopher Epicurus about 300 bc and well recorded in a long poem (On the Nature of Things) by the Roman Lucretius (c.99–55 bc). In the 17th-c Boyle and Newton were aware of these ideas; it is doubtful if they contributed at all directly to modern atomic theory, which began with Dalton about 1800.