They, then, who see their own mind, in whatever way that is possible, and in it that Trinity of which I have treated as I could in many ways, and yet do not believe or understand it to be an image of God, see indeed a glass, but do not so far see through the glass Him who is now to be seen through the glass, that they do not even know the glass itself which they see to be a glass, i.e. an image. And if they knew this, perhaps they would feel that He too whose glass this is, should by it be sought, and somehow provisionally be seen, an unfeigned faith purging their hearts, that He who is now seen through a glass may be able to be seen face to face. And if they despise this faith that purifies the heart, what do they accomplish by understanding the most subtle disputes concerning the nature of the human mind, unless that they be condemned also by the witness of their own understanding? And they would certainly not so fail in understanding, and hardly arrive at anything certain, were they not involved in penal darkness, and burdened with the corruptible body that presses down the soul. And for what demerit save that of sin is this evil inflicted on them? Wherefore, being warned by the magnitude of so great an evil, they ought to follow the Lamb that taketh away the sins of the world.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 1, vol. 3 (Schaff, 1887), public domain (Public domain).