Leucippus

Leucippus worked in the 5th century BCE, a direct answer to the Eleatics who insisted all things are one and emptiness cannot exist. He countered with atoms - infinite in form, locked in constant motion - and the void that lets them move. With his student Democritus he described a deterministic cosmos born from a vortex of atoms that spun out the Earth, Sun, and stars, and because both atoms and void are infinite, other worlds must exist elsewhere. The soul itself was spherical atoms cycling through breath, generating thought and sensation. Almost nothing survives: Aristotle and Theophrastus are the only sources, most of his writing is gone, and one sentence remains. Some scholars have wondered whether he existed at all or whether his ideas were entirely Democritus's, but the consensus holds and the split he proposed - matter and nothingness - still echoes.