Leucippus

Leucippus, who flourished in the fifth century BCE, was a pre-Socratic Greek philosopher traditionally credited as the founder of atomism, which he developed with his student Democritus. He divided the world into two entities, atoms, indivisible particles that make up all things, and the void, the nothingness that exists between the atoms, developing his philosophy as a response to the Eleatics, who believed that all things are one and the void does not exist. Leucippus held that atoms come in infinitely many forms and exist in constant motion, creating a deterministic world in which everything is caused by the collisions of atoms, and he described the beginning of the cosmos as a vortex of atoms that formed the Earth, the Sun, the stars and other celestial bodies; since he considered both atoms and the void infinite, he presumed other worlds must exist elsewhere. The only records of Leucippus come from Aristotle and Theophrastus, later ancient philosophers, and little is known of his life; most scholars agree he existed, though some have questioned this and attributed his ideas purely to Democritus, and contemporary philosophers rarely distinguish their respective ideas. Two works are attributed to him, The Great World System and On Mind, but all his writing has been lost except one sentence.