Democritus (c. 460–c. 370 BC)

Greek philosopher and speculative scientist who made a significant contribution to metaphysics with his atomic theory of the universe: all things originate from a vortex of tiny, indivisible particles, which he called atoms, and differ according to the shape and arrangement of their atoms.

Democritus' discussion of the constant motion of atoms to explain the origins of the universe was the most scientific theory proposed in his time. His concepts come to us through Aristotle's work in this area.

Democritus was born in Thrace and travelled widely in the East. He is reputed to have written more than 70 works, although only fragments have survived.

According to Democritus' theory, atoms cannot be destroyed (an idea similar to the modern theory of the conservation of matter) and they exist in a vacuum or void, which corresponds to the space between atoms. Atoms of a liquid are smooth and round; atoms of a solid are jagged and catch on to each other. Atoms differ only in shape, position, and arrangement.