Atomism

The atomists held that the world consists of two kinds of reality: atoms, which are indivisible, unchangeable and infinite in number, and the void in which they move. Everything we see is a cluster of atoms, and every change is atoms rearranging. Leucippus and Democritus are thought to have developed the theory in response to Parmenides, showing how change is possible without anything coming to be from nothing.

Of the ancient accounts of nature that did without purpose or design, atomism was the most influential. Epicurus inherited it from Democritus and reworked it in response to Aristotle’s criticisms, and it was taken up again in early modern Europe. Atomist theories were also developed independently in classical India.