Democritus
Democritus was a pre-Socratic Greek philosopher (born at Abdera in Thrace around 460 BC; lived to be very old and died in 370 B.C). Democritus was a student of Leucippus, and co-originator of the belief that all matter is made up of various imperishable indivisible elements which he called atoms. It is virtually impossible to tell which of these ideas were unique to Democritus, and which are attributable to Leucippus. Democritus is also the first philosopher we know who realized that what we perceive as the Milky Way is the light of distant stars. Other philosophers, including later Aristotle, argued against this. Democritus was among the first to propose that the universe contains many worlds, some of them inhabited:
- "In some worlds there is no Sun and Moon, in others they are larger than in our world, and in others more numerous. In some parts there are more worlds, in others fewer (...); in some parts they are arising, in others failing. There are some worlds devoid of living creatures or plants or any moisture."
He was also a pioneer of mathematics and geometry in particular. We only know this through citations of his works (titled On Numbers, On Geometrics, On Tangencies, On Mapping, and On Irrationals) in other writings, since most of Democritus' body of work did not survive the Middle Ages. Aristotle tells us that his theory of matter, commonly called atomism, was a reaction to Parmenides, who denied the existence of motion, change, or the void. Parmenides argued that the existence of a thing implied that it could not have "come into being", because "nothing comes from nothing". Moreover, he argued, movement was impossible, because one must move into "the void" and (as he identified "the void" with "nothing") the void does not exist and cannot be "moved into".

Stamp issued by Greece on Sept. 26, 1983 to honor an International Conference on Democritus and his work
External links
This article is part of The Presocratic Philosophers series
Thales | Anaximander | Anaximenes of Miletus | Pythagoras | Empedocles | Heraclitus | Parmenides | Xenophanes | Leucippus | Democritus | Protagoras | Gorgias | Prodicus

