Leucippus or Leukippos (Greek: Λεύκιππος, first half of 5th century BC) was the first to develop the theory of atomism — the idea that everything's composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in far greater detail by his pupil and successor, Democritus. He was born at Miletus or Abdera. Overview Leucippus's a shadowy figure, as his dates aren't recorded and he's often mentioned in con… (More on Leucippus)