Atomism

Atomism (from Ancient Greek ἄτομον (atomon) '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.The early concept of atomism can be traced back to ancient Greece. Leucippus is the earliest figure whose commitment to Greek atomism is well attested and 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.

A similar idea was developed by Kanāda of the Vaiśeṣika school, who proposed indivisible particles (paramāṇu). Indian Buddhists, such as Dharmakirti (fl. c. 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.

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.