Critias c. 460 BC – 403 BC

Critias was an Athenian aristocrat, sophist, tragedian, and statesman of the late fifth century BC and the most prominent of the Thirty Tyrants who ruled Athens after the city's defeat in the Peloponnesian War. A pupil of Socrates, an uncle of Plato, and a relative of Solon, he wrote tragedies, elegies, and prose works of which only fragments survive. His Sisyphus fragment, presenting religion as a human invention designed to deter wrongdoing, is one of the earliest surviving statements of the political theory of religion. He died in the civil war that ended the rule of the Thirty in 403 BC.

Critias the son of Callaeschrus was born around 460 BC into one of the most distinguished families of Athens, descended on his mother's side from Solon. He was the cousin of Plato's mother Perictione and a long-standing companion of Socrates, and appears as an interlocutor in Plato's Charmides, Protagoras, and Timaeus, and as the eponymous speaker of the unfinished Critias on the legend of Atlantis. He combined philosophy, poetry, and oligarchic politics throughout his career.

He was implicated in the brief oligarchic regime of the Four Hundred in 411 BC, exiled to Thessaly, and recalled to Athens after the city's defeat by Sparta in 404 BC. As the leading figure of the Thirty Tyrants in 404–403 BC he presided over a brutal purge of democrats and metics — most notoriously executing his moderate colleague Theramenes — before being killed in battle against Thrasybulus's democrats at Munychia in 403 BC. Surviving fragments of his elegies, hexameters, and prose Constitutions show literary as well as political ambition.

The famous 'Sisyphus fragment', preserved by Sextus Empiricus and now generally attributed to Critias rather than to Euripides, argues that the gods were invented by a shrewd lawgiver to instil a fear that would deter even secret wrongdoing — an early statement of the political theory of religion. His name became, in democratic memory, shorthand for the dangers of philosophical association with tyranny.