(fifth century B.C.), ancient Greek materialist philosopher. One of the founders of ancient atomism.

Very little is known about the life of Leucippus. He was a contemporary of Zeno of Elea, Empedocles, and Anaxagoras. His birthplace is considered to be Miletus, Elea, or Abdera. He probably taught in Abdera, where his student Democritus lived. Democritus created a complete atomic theory; as a philosopher, he totally overshadowed his teacher. The works of Leucippus have not been preserved.

At the same time as Empedocles and Anaxagoras, Leucippus advanced the idea of the plurality of elements in all that exists. He upheld Parmenides’ idea of the immutability and qualitative uniformity of that which exists. In order to explain the diversity of objects, Leucippus affirmed the existence of relative nonbeing, that is, the presence of a void that divides all existing things into a multiplicity of elements. The properties of these elements depend on the void space that limits them. Although they differ in shape, size, and movement, all elements are viewed as uniform, continuous, and therefore indivisible (atomoi). Consistent with the teachings of the philosophers of the Ionic school, Leucippus believed movement to be an internal, inherent property of atoms. It appears that certain aspects of atomistic cosmology, later developed by Democritus, may be attributed to Leucippus.