2 For when I read the words, “To Father Augustine, eternal salvation in the Lord,” I was suddenly elated with such fullness of hope, that I believed you either already converted to the Lord Himself, and to that eternal salvation of which He is the author, or desirous, through our ministry, to be so converted. But when I read the rest of the letter my heart was chilled. I inquired, however, from the bearer of the letter, whether you were already Christians or were desirous to be so.
After I learned from his answer that you were in no way changed, I was deeply grieved that you thought it right not only to reject the name of Christ, to whom you already see the whole world submitting, but even to insult His name in my person; for I could not think of any other Lord than Christ the Lord in whom a bishop could be addressed by you as a father, and if there had been any doubt as to the meaning to be attached to your words, it would have been removed by the closing sentence of your letter, where you say plainly, “We desire that, for many years, your lordship may always, in the midst of your clergy, be glad in God and His Christ.”
After reading and pondering all these things, what could I (or, indeed, could any man) think but that these words were written either as the genuine expression of the mind of the writers, or with an intention to deceive? If you write these things as the genuine expression of your mind, who has barred your way to the truth? Who has strewn it with thorns? What enemy has placed masses of rock across your path? In fine, if you are desiring to come in, who has shut the door of our places of worship against you, so that you are unwilling to enjoy the same salvation with us in the same Lord in whose name you salute us?
But if you write these things deceitfully and mockingly, do you, then, in the very act of imposing on me the care of your affairs, presume to insult, with the language of feigned adulation, the name of Him through whom alone I can do anything, instead of honouring Him with the veneration which is due to Him?
Source: Letters (New Advent)