“…[I]t is not allowable for anyone to produce another faith, that is, to write or to compose or to consider or to teach others; those who dare to compose another faith, or to support or to teach or to hand on another creed to those who wish to turn to knowledge of the truth, whether from Hellenism or Judaism or indeed from any heresy whatsoever, or to introduce novelty of speech, that is, invention of terms, so as to overturn what has now been defined by us, such persons, if they are bishops or clerics, are deprived of their episcopacy or clerical rank, and if they are monks or layfolk they are excommunicated.”
—Pope Saint Leo II, Third Council of Constantinople, c. A.D. 681
