According to Socrates in Plato's Philebos, the greatest misfortune to befall humankind is to be wilfully blind and ignorant, and to cover this up with the "false conceit of wisdom" (δοξοσοφίας ψεθδοῦς 49a).
It is the way in which humankind falls most short of the Delphic dictum, "Know thyself!" (γνῶθι σαυτόν 48c).
Welcome to the present day.