Leucippus

Leucippus was a pre-Socratic Greek philosopher active in the fifth century BCE and traditionally credited as the founder of atomism, which he developed together with his student Democritus. He divided the world into atoms, the indivisible particles that make up all things, and the void between them, and he framed this view as a reply to the Eleatics, who held that all is one and that no void exists. Two works are attributed to him, The Great World System and On Mind, but all of his writing is lost except a single sentence, that nothing happens at random but everything for a reason and by necessity. The only records of him come from Aristotle and Theophrastus, little is known of his life, and a few scholars have doubted that he existed and have credited his ideas to Democritus alone. He belongs in the atlas as the earliest named author of the atomist tradition.