The Sisyphus fragment is a 5th-century BC play thought to contain an atheistic argument.
Contents
Some shrewd and intelligent man invented fear of the gods for mortals, so the wicked would have something to fear ... concealing the truth with a false account
Authorship
The authorship of the Sisyphus Fragment remains in question. While most scholars attribute it to Critias, including ancient sources such as Sextus Empiricus, some claim Euripides as the author. We know that Critias earned a reputation for atheism in later antiquity, but that is likely due to his presumed authorship of this fragment.
Complications
The Sisyphus fragment is problematic due to its nature as a fragment of a lost Satyr play. Even were the author of the fragment known for certain, its inclusion in a 'tragicomedy' further insulates the sentiment being expressed in the play from any earnest argument the author may or may not be making.