important Greek thinker in the development of atheism was Epicurus ( 300 BCE). Drawing on the ideas of Democritus and the Atomists, he espoused a materialistic philosophy according to which the universe was governed by the laws of chance without the need for divine intervention (see scientific determinism). Although Epicurus still maintained that the gods existed, he believed that they were uninterested in human affairs. The aim of the Epicureans was to attain ataraxia (a mental state of being untroubled). One important way of doing this was by exposing fear of divine wrath as irrational. The Epicureans also denied the existence of an afterlife and the need to fear divine punishment after death. One of the most eloquent expressions of Epicurean thought is Lucretius' On the Nature of Things (1st century BCE) in which he held that gods exist but argued that religious fear was one of the chief causes of human unhappiness and that the gods did not involve themselves in the world. The Epicureans also denied the existence of an afterlife and hence dismissed the fear of death. Epicureans denied being atheists but their critics insisted they were. One explanation for this alleged crypto-atheism is that they feared persecution, and while they avoided this their teachings were controversial and harshly attacked by some of the other schools, particularly Stoicism and Neoplatonism. Pyrrhonism Similar to the Epicureans, the Pyrrhonists employed a tactic to avoid persecution for atheism in which they, in conformity with ancestral customs and laws, declared that the gods exist, and performed everything which contributes to their worship and veneration, but, with regard to philosophy, declined to commit themselves to the gods' existence. The Pyrrhonist philosopher Sextus Empiricus compiled a large number of ancient arguments against the existence of gods, recommending that one should suspend judgment regarding the matter. His large volume of surviving works had a lasting influence on later philosophers. Medicine In pre-Hippocratic times, Greeks believed that gods controlled all aspects of human existence, including health and disease. One of the earliest works that challenged the religious view was On the Sacred Disease, written about 400 B.C. The anonymous author argued that the "sacred disease" of epilepsy has a natural cause, and that the idea of its supposed divine origin is based on human inexperience. The Middle Ages Islamic world In the early history of Islam, Muslim scholars recognized the idea of atheism and frequently