His physics (later expounded by the Roman writer Lucretius) is based on the theory of a materialist Universe, unregulated by divine providence, composed of indestructible atoms moving in a void. From this follows his philosophy of Epicureanism, a restrained type of hedonism: mental pleasure was regarded more highly than physical and the ultimate pleasure was held to be freedom from anxiety and mental pain, especially that arising from needless fear of death and of gods.