Nicene and Post-Nicene Fathers, Vol. V:
A Treatise on Nature and Grace.: Chapter 7

Chapter 7 [VII.]—He Proceeds to Confute the Work of Pelagius; He Refrains as Yet from Mentioning Pelagius’ Name.

However ardent, then, is the zeal which the author of the book you have forwarded to me entertains against those who find a defence for their sins in the infirmity of human nature; not less, nay even much greater, should be our eagerness in preventing all attempts to render the cross of Christ of none effect. Of none effect, however, it is rendered, if it be contended that by any other means than by Christ’s own sacrament it is possible to attain to righteousness and everlasting life. This is actually done in the book to which I refer—I will not say by its author wittingly, lest I should express the judgment that he ought not to be accounted even a Christian, but, as I rather believe, unconsciously. He has done it, no doubt, with much power; I only wish that the ability he has displayed were sound and less like that which insane persons are accustomed to exhibit.