<P> Atomism (from Greek ἄτομον, atomon, i.e. "uncuttable, indivisible") is a natural philosophy that developed in several ancient traditions . </P> <P> References to the concept of atomism and its atoms appeared in both ancient Greek and ancient Indian philosophical traditions . The ancient Greek atomists theorized that nature consists of two fundamental principles: atom and void . Unlike their modern scientific namesake in atomic theory, philosophical atoms come in an infinite variety of shapes and sizes, each indestructible, immutable and surrounded by a void where they collide with the others or hook together forming a cluster . Clusters of different shapes, arrangements, and positions give rise to the various macroscopic substances in the world . </P>

From the ancient greek meaning indivisible units of matter
find me the text answering this question