Cephalus quotes Sophocles thus in Plato's Republic, a Socratic dialogue written around 380 B.C.. In the book, Socrates argues with various other figures including Cephalus about the nature of justice and the proper way to run a city state such as Athens. Plato used the work to put forward his ideas about politics and justice, as well as his Theory of Forms.
Sophocles (c.497-406 B.C.) was an Ancient Greek dramatist, famous for tragedies such as the Theban plays, including Oedipus Rex, which was the starting point for Freud's theory of the Oedipus complex.