Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Donatist Controversy.: Chapter 30

Chapter 30.—68.  Petilianus said:  "Or if any one chance to recollect the chants of a priest, is he therefore to be deemed a priest, because with sacrilegious mouth he publishes the strain of a priest?"

69.  Augustin answered:  In this question you are speaking just as though we were at p. 547 present inquiring what constituted a true priest, not what constituted true baptism.  For that a man should be a true priest, it is requisite that he should be clothed not with the sacrament alone, but with righteousness, as it is written, "Let thy priests be clothed with righteousness." 2063   But if a man be a priest in virtue of the sacrament alone, as was the high priest Caiaphas, the persecutor of the one most true Priest, then even though he himself be not truthful, yet what he gives is true, if he gives not what is his own but what is God’s; as it is said of Caiaphas himself, "This spake he not of himself:  but being high priest that year, he prophesied." 2064   And yet, to use the same simile which you employed yourself:  if you were to hear even from any one that was profane the prayer of the priest couched in the words suitable to the mysteries of the gospel, can you possibly say to him, Your prayer is not true, though he himself may be not only no true priest, but not a priest at all? seeing that the Apostle Paul said that certain testimony of I know not what Cretan prophet was true, though he was not reckoned among the prophets of God for he says, "One of themselves, even a prophet of their own, said the Cretians are always liars, evil beasts, slow bellies:  this witness is true." 2065   If, therefore, the apostle even himself bore witness to the testimony of some obscure prophet of a foreign race, because he found it to be true, why do not we, when we find in any one what belongs to Christ, and is true even though the man with whom it may be found be deceitful and perverse, why do not we in such a case make a distinction between the fault which is found in the man, and the truth which he has not of his own but of God’s? and why do we not say, This sacrament is true, as Paul said, "This witness is true"?  Does it at all follow that we say, The man himself also is truthful, because we say, This sacrament is true?  Just as I would ask whether the apostle counted that prophet among the prophets of the Lord, because he confirmed the truth of what he found to be true in him.  Likewise the same apostle, when he was at Athens, perceived a certain altar among the altars of the false gods, on which was this inscription, "To the unknown God."  And this testimony he made use of to build them up in Christ, to the extent of quoting the inscription in his sermon, and adding, "Whom, therefore, ye ignorantly worship, Him declare I unto you."  Did he, because he found that altar among the altars of idols, or set up by sacrilegious hands, therefore condemn or reject what he found in it that was true? or did he, because of the truth which he found upon it, therefore persuade them that they ought also to follow the sacrilegious practices of the pagans?  Surely he did neither of the two; but presently, when, as he judged fitting, he wished to introduce to their knowledge the Lord Himself unknown to them, but known to him, he says among other things, that "He is not far from every one of us:  for in Him we live, and move, and have our being; as certain also of your own poets have said." 2066   Can it be said that here also, because he found among the sacrilegious, the evidence of truth, he either approved their wickedness because of the evidence, or condemned the evidence because of their wickedness?  But it is unavoidable that you should be always in the wrong, so long as you do despite to the sacraments of God because of the faults of men, or think that we take upon ourselves the sacrilege even of your schism, for the sake of the sacraments of God, to which we are unwilling to do despite in you.

Footnotes

Ps. cxxxii. 9.

John xi. 51.

Titus 1:12, 13.

Acts 17:23, 27, 28.