“21. It is an act of great piety to expose the concealments of the impious and to defeat there the devil himself, whose slaves they are... 30. Therefore We entreat you to use every means of revealing to your faithful people the many kinds of plot, pretense, error, deceit and contrivance which our enemies use. This will turn them carefully away from infectious books. Also exhort them unceasingly to flee from the sects and societies of the impious as from the presence of a serpent, earnestly avoiding everything which is at variance with the wholeness of faith, religion and morality…”  Pope Pius IX, Qui Pluribus, 1846: