31. Ep. 87.1–5 (CCL 31A:131–35); trans. Parsons, FOTC 18:12–17.
I do not know why [you chose this separation]. For it is certain that a large part of the Roman world, not to mention the barbarian tribes to which the Apostle said he was also a debtor, with whose Christian faith our own is intertwined, knows nothing of the sect of Donatus, nor have they any idea when or from what cause that dissension arose. Assuredly, unless you admit that all those Christians [worldwide] are innocent of the charges that you make against the Africans, you are forced to say that all of you are guilty of the evil deeds of all, since there lurk among you, to put it mildly, some misguided characters. You do not expel anyone, or at least you only expel him when he has done something that requires expulsion. Or is it that you do not condemn someone who has been in hiding for some time and is afterward betrayed and convicted? I ask, therefore, whether he contaminated you during the time he was in hiding? You will answer: "Not at all." Then if he remained in hiding the whole time, he would not contaminate you at all, for it often happens that after people die their deeds come to light, but this is no harm for the Christians who lived in contact with them during their lifetime. Why, then, have you, by a rash and accursed schism, cut yourselves off from communion with innumerable Eastern churches, which knew nothing of what happened in Africa according to what you teach or claim?
(2) Whether what you say is true is another question, while we prove your facts to be false by much more authoritative documents, and we hold that this is proved even better by your own documents, in regard to the charges which you make against us. But, as I said, this is another question, one to be taken up and discussed when need arises. Turn the attention of your mind now upon this: that no one can be contaminated by the unknown crimes of unknown people. From this it is clear that you are separated by a sacrilegious schism from communion with the rest of the world, to which the charges, true or false, which you make against the Africans are completely unknown and have always been unknown. . . .
(5) How could the betrayers (traditores) among the Africans, whoever they may have been, have been known to the churches of the Corinthians, the Ephesians, the Colossians, the Philippians, the Thessalonians, the Antiochenes, the Pontians, the Cappadocians, and people of the other parts of the world, evangelized by the apostles and brought to Christ, or how did they deserve to be condemned by you if they could not have been known? Yet you are not in communion with them, and you say that they are not Christians, and you attempt to rebaptize them. What more is to be said? It makes me want to complain and to cry out.31
31. Ep. 87.1–5 (CCL 31A:131–35); trans. Parsons, FOTC 18:12–17.