Communium Rerum §43

⁴³ But unfortunately their grandiloquent phrases and their promises of a new wisdom, fallen as it were from heaven, and of new methods of thought, have found favor with many young men, as those of the Manicheans found favor with Augustine, and have returned these aside, more or less unconsciously, from the right road. But concerning such pernicious masters of an insane knowledge, of their aims, their illusions, their erroneous and disastrous systems, We have spoken at great length in Our Encyclical Letter of September 8, 1907, "Pascendi dominici gregis."