To his most pious brother Gregory. Peter greeting in the Lord.
Having met with the writings of your holiness and having perceived in your tract against this heresy your zeal both for the truth and for our sainted father in God, I judge that this work was not due simply to your own ability, but was that of one who studied that the Truth should speak, even in the publication of his own views. To the Holy Spirit of truth I would refer this plea for the truth; just as to the father of lies, and not to Eunomius, should be referred this animosity against sound faith. Indeed, that murderer from the beginning who speaks in Eunomius has carefully whetted the sword against himself; for if he had not been so bold against the truth, no one would have roused you to undertake the cause of our religion. But to the end that the rottenness and flimsiness of their doctrines may be exposed, He who "taketh the wise in their own craftiness" hath allowed them both to be headstrong against the truth, and to have laboured vainly on this vain speech.
But since he that hath begun a good work will finish it, faint not in furthering the Spirit's power, nor leave half-won the victory over the assailants of Christ's glory; but imitate thy true father who, like the zealot Phineas, pierced with one stroke of his Answer both master and pupil. Plunge with thy intellectual arm the sword of the Spirit through both these heretical pamphlets, lest, though broken on the head, the serpent affright the simpler sort by still quivering in the tail. When the first arguments have been answered, should the last remain unnoticed, the many will suspect that they still retain some strength against the truth.
The feeling shewn in your treatise will be grateful, as salt, to the palate of the soul. As bread cannot be eaten, according to Job, without salt, so the discourse which is not savoured with the inmost sentiments of God's word will never wake, and never move, desire.
Be strong, then, in the thought that thou art a beautiful example to succeeding times of the way in which good-hearted children should act towards their virtuous fathers.