The Arian Heresy opened theological questions besides the nature of Christ. Once the heresy had been suppressed, former Arians sought communion with the Church. This presented a theological problem for the Early Church, because some of these people had first received Baptism at the hands of Arians. Was Baptism by heretics valid? This question sparked lively debate.
The question would eventually be settled by Pope St. Stephen (that the Baptisms were, indeed, valid). But (as is the ordinary custom), before promulgating the definitive teaching as Pope, Stephen participated in the preceding debate in his capacity as Bishop. Acting as Bishop, he advocated the idea that Baptism by heretics was valid.
St. Cyprian of Carthage is my favorite Early Church Father. He controlled Northern Africa. His prestige and influence was so great that his contemporary nickname was “the African Pope.”
It is difficult to overstate Cyprian’s opposition to the idea that Baptism by heretics was valid. A large body of his writing survives, and much of it is dedicated to this topic. He would often not even use the word “baptize” in this context - he referred to “those made wet by heretics.” I think that’s funny. In other writings, he used language so harsh that it would have probably earned him an infraction on this Forum.
In his Letter to Jubaianus (AD 255), a Bishop in Mauretania, Cyprian refers to a Council of African Bishops which agreed that:
Cyprian to Jubaianus his brother, greeting. You have written to me, dearest brother, wishing that the impression of my mind should be signified to you, as to what I think concerning the baptism of heretics; who, placed without, and established outside the Church, arrogate to themselves a matter neither within their right nor their power. This baptism we cannot consider as valid or legitimate, since it is manifestly unlawful among them; and since we have already expressed in our letters what we thought on this matter, I have, as a compendious method, sent you a copy of the same letters, what we decided in council when very many of us were present, and what, moreover, I subsequently wrote back to Quintus, our colleague, when he asked about the same thing. And now also, when we had met together, bishops as well of the province of Africa as of Numidia, to the number of seventy-one, we established this same matter once more by our judgment, deciding that there is one baptism which is appointed in the Catholic Church; and that by this those are not re-baptized, but baptized by us, who at any time come from the adulterous and unhallowed water to be washed and sanctified by the truth of the saving water.[73,1]
OK, this is HERESY before the fact (a heretical opinion expressed before the Church taught otherwise).
Writing to Cyprian, Firmillian, Bishop of Caesarea in Cappadocia, agreed with Cyprian, saying,
But what is his [Pope St. Stephen] error, and how great his blindness, who says that the remission of sins can be given in the synagogues of the heretics [Firmillian, *Letter to Cyprian
(AD 255), 75,16]
At this point, Cyprian and Firmillian were expressing their opposition to the opinion of Pope St. Stephen, but not in his capacity as Pope, but only as Bishop.
Alas, to nobody’s surprise, Bishop Stephen eventually acted in his official capacity as Pope Stephan and promulgated the teaching that Baptism by heretics was valid, and those Baptized by Arians were to be admitted to full Communion without undergoing any further Baptismal ceremony.
After that happened, Firmillian and Cyprian shut up about the matter (not even the otherwise prolific and single-minded Cyprian had anything else to say). We have no record of either having any continued opposition to this teaching. Likewise, we have no record of either publicly affirming the teaching, but Cyprian was the type of man to quietly accept his defeat but not champion his opponent.
Had Cyprian continued his opposition after Pope Stephen’s teaching, he would be considered a heretic after the fact, and would surely not be considered a Saint and Early Father of the Church today.