From Nick Denyer:
What other musical works are based upon ancient Greek philosophy?
From Klaus Döring's fascinating "Socrate sur la scene de l'opera", Philosophie Antique: Problemes, Renaissances, Usages, 1 (2001) 205-220, I learn of Socrates operas by Ernst Krenek (Pallas Athene Weint, 1955) and Antonio Draghi (La Patienza di Socrate con Due Moglie, 1680). Krenek wrote his own words; Draghi used words by Nicolo Minato. Draghi/Minato did other pieces too, among them Gl'Atomi di Epicuro (1672).
Telemann, too, wrote an opera, The Patience of Socrates and his Two Wives (Der geduldige Sokrates), although not as philosophical as Cole Porter, it seems.Do not forget the way that the winged souls of Plato's Phaedrus reappear as the fairies in Gilbert and Sullivan's Iolanthe.And there is the influence of Heraclitus' doctrines of the unity of opposites, and the flux, on Cole Porter: "Wrong's right today, and day's night today, and black's white today; and heaven knows, anything goes."