27 Conclusion.
Dionysius knew this when he wrote. And by his first letters he silenced Sabellius, and in his others he overcame the heresy of Arius. For just as the human attributes of the Saviour overthrew Sabellius, so against the Arian madmen one must use proofs drawn not from the human attributes but from what betokens the deity of the Word, lest they pervert what is said of the Lord by reason of His Body, and think that the Word is of like nature with us men, and so abide still in their madness. But if they also are taught about His deity they will condemn their own error; and when they understand that the Word was made flesh, they too will the more easily distinguish in future the human characteristics from those which fit His deity. But this being so, and the Bishop Dionysius having been shown by his writings to be pious, what will the Arian madmen do next? Convicted on this evidence, whom will they again venture to malign? For they needs must, since they have fallen from the foundation of the Apostles and have no settled mind of their own, seek some support, and if they can find none, then malign the fathers. But no one will believe them any more even if they make efforts to libel them, for the heresy is condemned on all hands. Unless perchance they will henceforth speak of the devil, for he is their only partisan, or rather he it is who suggested their heresy to them. Who then can any longer call men 'Christians' whose leader is the devil, and not rather 'Diabolici,' so that they may bear the name not merely of adversaries of Christ, but of partisans of the devil? Unless indeed they change round, and, rejecting the impiety they have contrived, come to know the truth. For this will at once be for their own good, and it is thus that it beseems us to pray for all those that are in error.
Source: De Sententia Dionysii (New Advent)