<P> Atomism (from Greek ἄτομον, atomon, i.e. "uncuttable", "indivisible") is a natural philosophy that developed in several ancient traditions . The 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> <P> References to the concept of atomism and its atoms are found in ancient India and ancient Greece . In the West, atomism emerged in the 5th century BCE with Leucippus and Democritus . In India the Jain, Ajivika and Carvaka schools of atomism may date back to the 4th century BCE . The Nyaya and Vaisheshika schools later developed theories on how atoms combined into more complex objects . </P> <P> The particles of chemical matter for which chemists and other natural philosophers of the early 19th century found experimental evidence were thought to be indivisible, and therefore were given the name "atom", long used by the atomist philosophy . </P>

Who developed the theory of atomism and believed that all things consist of particles called atoms
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