Athanasius of Alexandria - A Defense of the Nicene Definition (De Decretis)

And do thou, beloved, consider whether it be not so. If, the devil having sown their hearts with this perverseness, they are so confident in the truth of their reasonings, why do they not first clear themselves of the charge of heresy which lies against them? and then will come the time for them to criticise the definition of the Council. For no one, on being convicted of murder or adultery, is at liberty after the trial to arraign the sentence of the judge, why he spoke in this way and not in that. For this, instead of exculpating the convict, rather increases his crime on the score of petulance and audacity. Why did not they find fault with the wording of the definition at the time when it was framed? but now when their first duty is to repeat after the Council those anathemas in which its creed ends, instead of this, they profess to have scruples as to the creed itself, and they find matter for a subterfuge in the fact, which no one denies, that the word substance is not in Scripture. Surely it is just that those who are under a charge should confine themselves to their own defence. While their own conscience is so unclean, they are not quite the men to quarrel with an act which in truth they do not understand. Rather, let them investigate the matter in a docile spirit, and, in order to learn what hitherto they had not known, let them cleanse their ears in the stream of truth and the doctrine of piety.

Now it happened to the Eusebians in the Nicene Council in this wise:On their making a stand in behalf of their impiety, the assembled bishops, who were more or less three hundred in number, mildly and courteously called upon them to explain and defend themselves. Scarcely, however, did they begin to speak, when they pronounced their own condemnation, for one differed from another; then, perceiving the serious straits in which their heresy lay, they remained dumb, and by their silence confessed the disgrace which came upon them. On this the Bishops, after condemning the formul which they had devised, published against them the sound and ecclesiastical faith; and, whereas all subscribed it, the Eusebians subscribed it too in those very phrases, of which they are now complaining, (I mean, Of the substance, and Consubstantial,) professing that the Son of God is neither creature nor work, nor in the number of things made from nothing, but that the Word is an Offspring from the substance of the Father. And, what is strange indeed, Eusebius of Csarea in Palestine, who had refused the day before, yet afterwards subscribed, and sent to his church a letter, saying that this was the Churchs faith and the tradition of the Fathers; and thereby made it clear to all that his party were in error before, and were rashly contending against the truth. For, though he was ashamed at the moment to adopt these phrases, and excused himself to his Church in his own way, yet he certainly means to signify his acceptance of them, in that he does not in his Epistle deny the One in substance, and Consubstantial. And in this way he got into a difficulty; for, in excusing himself, he thereby was attacking the Arians, as if their stating that the Son was not before His generation, was their denial of His existence even before His birth in the flesh. And Acacius too knows this well, though he also through fear may pretend otherwise because of the times, and may deny the fact. Accordingly I have subjoined at the end of these remarks the letter of Eusebius, that thou mayst know from it the scanty regard shown by Christs enemies towards their own masters, and singularly by Acacius himself.