Epicureanism is a Hellenistic school or system of philosophy based on the teachings of the ancient Greek philospher Epicurus. It was founded around 307 B.C., and was based in Epicurus' home and garden (the school was often called "The Garden"). Epicurus was a materialist, following in the steps of Democritus and the school of Atomism.
In Ethics, Epicureanism teaches that happiness (or the greatest good) is to seek modest pleasures in order to attain a state of tranquillity, freedom from fear and the absence of bodily pain. This state of tranquillity can be obtained through knowledge of the workings of the world, the leading of a simple, moderate life and the limiting of desires (see the section on the doctrine of Epicureanism for more details).
In Metaphysics, Epicureanism emphasizes the neutrality of the gods and their non-interference with human lives. Despite some tendencies towards Atheism, it does not actually deny the existence of gods, which it conceives of as blissful and immortal, yet material, beings, made up of atoms and inhabiting the empty spaces between worlds in the vastness of infinite space.
Epicureanism was originally conceived by Epicurus as a challenge to Platonism, although, arguably, Democritus had propounded a very similar philosophy almost a century earlier. It built on the Hedonism of Aristippus (c. 435 - 360 B.C.) and Cyrenaics, differing from that movement mainly in its belief that one should defer immediate gratification for the sake of long-term gain, and that bodily gratification is not necessarily preferable to mental pleasures. Later, it became (along with Stoicism and Skepticism) one of the three dominant schools of Hellenistic philosophy, lasting strongly through the later Roman Empire.
During Epicurus' lifetime, its members included Hermarchus (who succeeded Epicurus as the head of his school in about 270 B.C.), Idomeneus (310 - 270 B.C.), Colotes (3rd Century B.C.), Polyaenus (c. 340 - 278 B.C.) and Metrodorus (331 - 277 B.C.), most of these from the Greek city of Lampsacus, where Epicurus taught his school before relocating to Athens.
Lucretius (99 - 55 B.C.) was the school's greatest Roman proponent, composing an epic poem, "De Rerum Natura" ("On the Nature of Things") on the Epicurean philosophy of nature. The poet Horace (65 - 8 B.C.) and Julius Caesar (100 - 44 B.C.) both leaned considerably toward Epicureanism.
After the official approval of Christianity by the Roman Emperor Constantine (272 - 337) in 313 A.D., Epicureanism was repressed as essentially irreconcilable with Christian teachings, and the school endured a long period of obscurity and decline.
In more modern times, the French philosopher and priest Pierre Gassendi (1592 - 1655) referred to himself as an Epicurean (and attempted to revived the doctrine), as did Thomas Jefferson (1743 - 1826) and the Utilitarian Jeremy Bentham (1748 - 1832).