An actor I know is a dimwit who can't count higher than the fingers on his hands. But once he gets on stage, the audience goes so wild, you'd think the house would split in two.
满口仁义道理，但内心却充满邪念，只责怪他人而从不责骂自己，这种人称为“挂榜圣贤”。只怕恶行为人所见，能敬畏鬼神，知人又知天理，这才是实际的学问。
One is not struck by the truth until prompted quite accidentally by some external event.