These things, then, being as I have stated them, it is now evident that there has arisen a deadly heresy, which, with the Lord’s help, the Church by this time guards against more directly—now that those two men, Pelagius and Cœlestius, have been either offered repentance, or on their refusal been wholly condemned. They are reported, or perhaps actually proved, to be the authors of this perversion; at all events, if not the authors (as having learnt it from others), they are yet its boasted abettors and teachers, through whose agency the heresy has advanced and grown to a wider extent. This boast, too, is made even in their own statements and writings, and in unmistakeable signs of reality, as well as in the fame which arises and grows out of all these circumstances. What, therefore, remains to be done? Must not every catholic, with all the energies wherewith the Lord endows him, confute this pestilential doctrine, and oppose it with all vigilance; so that whenever we contend for the truth, compelled to answer, but not fond of the contest, the untaught may be instructed, and that thus the Church may be benefited by that which the enemy devised for her destruction; in accordance with that word of the apostle’s, “There must be heresies, that they which are approved may be made manifest among you”?
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 1, vol. 5 (Schaff, 1887), public domain (Public domain).