Atomism

Atomism (from Greek ἄτομον, atomon, i.e. "uncuttable, indivisible") is a natural philosophy proposing that the physical universe is composed of fundamental indivisible components known as atoms. References to the concept of atomism and its atoms appeared in both ancient Greek and ancient Indian philosophical traditions. Leucippus is the earliest figure whose commitment to atomism is well attested and he is usually credited with inventing atomism. He and other ancient Greek atomists theorized that nature consists of two fundamental principles: atom and void. Clusters of different shapes, arrangements, and positions give rise to the various macroscopic substances in the world. 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 by John Dalton the name "atom", long used by the atomist philosophy. Although the connection to historical atomism is at best tenuous, elementary particles have become a modern analogue of philosophical atoms. Philosophical atomism is a reductive argument, proposing not only that everything is composed of atoms and void, but that nothing they compose really exists: the only things that really exist are atoms ricocheting off each other mechanistically in an otherwise empty void. Atomism stands in contrast to a substance theory wherein a prime material continuum remains qualitatively invariant under division (for example, the ratio of the four classical elements would be the same in any portion of a homogeneous material). Indian Buddhists, such as Dharmakirti ( 6th or 7th century) and others, developed distinctive theories of atomism, for example, involving momentary (instantaneous) atoms (kalapas) that flash in and out of existence. In the 5th century BC, Leucippus and his pupil Democritus proposed that all matter was composed of small indivisible particles which they called "atoms". Nothing whatsoever is known about Leucippus except that he was the teacher of Democritus.