Almost nothing is known with certainty about the life of Leucippus (lew-SIHP-uhs), who is believed to have proposed the atomic hypothesis between 440 and 430 b.c.e. He was probably born in Miletus and spent part of his life in Abdera, where he was the teacher of Democritus, who elaborated on Leucippus’s hypothesis. He also may have traveled to Elea, where he met the philosopher Zeno of Elea. The later Greek atomist Epicurus claimed that Leucippus never existed, possibly out of jealousy. Aristotle and Theophrastus both refer to him in their writings as the founder of atomism.