He came from Abdera in Thrace. His philosophy was based on that of an earlier philosopher Leucippus, and was itself the precursor of the materialist philosophy of Epicurus.

He said:

According to convention, there is a sweet and a bitter, a hot and a cold; according to convention there is a colour. In truth there are atoms and a void.
The theory is preserved in discussion by later writers, principally Aristotle. None of his own writings survive, but those quotations that have been preserved largely relate to ethics.

Robert Burton (1577-1640) used the by-name Democritus in his The Anatomy of Melancholy.