Leucippus is traditionally credited with initiating atomism: an explanation of change through innumerable indivisible bodies moving in empty space.
Intellectual setting
Leucippus's historical identity and relation to Democritus are uncertain, but ancient testimonies consistently place him at atomism's origin.
Key ideas
Atoms and void
What is real includes solid indivisible bodies and the empty space required for their motion.
Mechanical explanation
Compounds and their qualities result from the arrangement, shape, and movement of imperceptible bodies.
Legacy
The Leucippus tradition established the conceptual pairing of atoms and void that Epicureans later adapted.
Scholarly notes
Leucippus and Democritus · resolved
Almost nothing by Leucippus survives, and ancient reports credit Democritus with taking over and systematising the theory, so the atomist doctrine cannot be divided between the two; the corpus is treated as joint by convention rather than by evidence.