Atheism is older than Christianity. The first explicit atheists in Western civilization can be found among the ancient Greeks. The word atheism stems from the Greek "atheos" or "without God." The first self-proclaimed atheist was Diagoras of Melos, who lived in ancient Athens in the 5^th century B. C. Diagoras was a student of Democritus, the atomist philosopher. He denied the existence of the official gods of the Athenian city-state, since the gods did not seem to punish many vicious acts that they were supposed to have condemned. Just as religious intolerance plagues much of the world today, so did it then. Diagoras was exiled from Athens for his overtly atheistic statements and spent the remainder of his life in Corinth.

Circa 300 B. C., Theodorus the Atheist of Cyrene denied the existence of any gods and believed in a this-worldly purpose to life. Theodorus argued that the goal of life was to pursue joy and escape grief, rather than seeking to worship any gods or obtaining any kind of afterlife. Theodorus made the connection between prudence and joy as well as between folly and grief - suggesting that it is our own wise conduct that leads to our joy, and our own foolish conduct that leads to our grief. Later writers, including Cicero and Plutarch, gave Theodorus the name Atheus, whence he became known as Theodorus the Atheist. For his freethinking ways, Theodorus was banished from both Cyrene and Athens and - as an ambassador - apparently offended a few rulers with whom he tried to share his ideas. Through his book, On the Gods, Theodorus inspired the great philosopher Epicurus, who further developed Theodorus's orientation toward pursuing happiness and avoiding grief.

Epicurus himself, while not an explicit atheist, formed a philosophy of life that atheists would have no problem with. If there were gods, argued Epicurus, they had nothing to do with human affairs and left people to fend for themselves - a point of view resurrected by the Deists of the 18^th century.

Atheism was unfortunately stifled in the Western world by the rise of fanatical and intolerant strains of Christianity during the late Roman Empire. In 381 A. D., the Roman emperor Theodosius I issued a decree banning any religious or non-religious views departing from his official interpretation of Christian doctrine. Explicit atheism did not fully revive until the late 18^th century, with such thinkers as the Baron d'Holbach and the Marquis de Condorcet.