  Democritus, known in antiquity as the ‘laughing philosopher’ because of his emphasis on the value of ‘cheerfulness,’ was one of the two founders of ancient atomist theory.  He elaborated a system originated by his teacher Leucippus into a materialist account of the natural world.  The atomists held that there are smallest indivisible bodies from which everything else is composed, and that these move about in an infinite void.  Of the ancient materialist accounts of the natural world which did not rely on some kind of teleology or purpose to account for the apparent order and regularity found in the world, atomism was the most influential.  Even its chief critic, Aristotle, praised Democritus for arguing from sound considerations appropriate to natural philosophy.