Epicureanism is a system of philosophy based upon the teachings of Epicurus, founded around 307 BC. Epicurus was an atomic materialist, following in the steps of Democritus. His materialism led him to a general attack on superstition and divine intervention. Following Aristippus—about whom very little is known—Epicurus believed that pleasure is the greatest good. But the way to attain pleasure was to live modestly and to gain knowledge of the workings of the world and the limits of one's desires. This led one to attain a state of tranquility (ataraxia) and freedom from fear, as well as absence of bodily pain (aponia). The combination of these two states is supposed to constitute happiness in its highest form. Although Epicureanism is a form of hedonism, insofar as it declares pleasure as the sole intrinsic good, its conception of absence of pain as the greatest pleasure and its advocacy of a simple life make it different from "hedonism" as it is commonly understood.
Epicureanism was originally a challenge to Platonism, though later it became the main opponent of Stoicism. Epicurus and his followers shunned politics. After the death of Epicurus, his school was headed by Hermarchus; later many Epicurean societies flourished in the Late Hellenistic era and during the Roman era (such as those in Antiochia, Alexandria, Rhodes, and Ercolano). The poet Lucretius is its most well-known Roman proponent. By the end of the Roman Empire, having undergone Christian attack and repression, Epicureanism had all but died out, and would be resurrected in the 17th century by the atomist Pierre Gassendi, who adapted it to the Christian doctrine.