Critias is also a work by Plato, see [1] (http://classics.mit.edu/Plato/critias.html) for a translation.

Critias, 460-403 BC, was the uncle of Plato, leading member of the Thirty Tyrants, and one of the most violent. He was an associate of Socrates', a fact that did not endear Socrates to the Athenian public. He was noted in his day for his tragedies, elegies and prose works. From his Sisyphus a fragment has been preserved in which he declares faith in the gods to be merely a clever device for holding the masses in check; but as no one would dare to make such a statement before an Athenian audience, the piece was probably intended only for private reading.