21 L. The account I used before to hear given of these things was widely different, and, as I now think, better calculated to promote error than hope. But I thank Christ my God for pouring into my heart the light of truth, that I might no longer profanely call the Church, which is His Virgin, the harlot of the devil. There is one other point I should like you to explain. What are we to say about Hilary who does not receive even those who have been baptized by the Arians?
O. Since Hilary when he left the Church was only a deacon, and since the Church is to him, though to him alone, a mere worldly multitude, he can neither duly celebrate the Eucharist, for he has no bishops or priests, nor can he give baptism without the Eucharist. And since the man is now dead, inasmuch as he was a deacon and could ordain no one to follow him, his sect died with him. For there is no such thing as a Church without bishops. But passing over a few very insignificant persons who are in their own esteem both laymen and bishops, let me point out to you what views we should hold respecting the Church at large.
L. You have settled a great question in three words, as the saying is, and indeed while you speak, I feel that I am on your side. But when you stop, some old misgivings arise as to why we receive those who have been baptized by heretics.
O. That is just what I had in mind when I said I would point out what views we ought to hold concerning the Church at large. For many are exercised by the misgivings you speak of. I shall perhaps be tedious in my explanation, but it is worth while if the truth gains.
Source: The Dialogue Against the Luciferians (New Advent)