“And for this reason did the Word become the dispenser of the paternal grace for the benefit of men, for whom He made such great dispensations, revealing God indeed to men, but presenting man to God, and preserving at the same time the invisibility of the Father, lest man should at any time become a despiser of God, and that he should always possess something towards which he might advance; but, on the other hand, revealing God to men through many dispensations, lest man, falling away from God altogether, should cease to exist. For the glory of God is a living human being; and the life of man consists in beholding God. For if the manifestation of God which is made by means of the creation, affords life to all living in the earth, much more does that revelation of the Father which comes through the Word, give life to those who see God.” St. Irenaeus of Lyons, Against Heresies 4, Chapter 20, Tract 7.
As Fagerberg explains in a footnote in his Book, “On Liturgical Asceticism”, “It was an ancient understanding that the eye seized the object it looked up and took it into onself. So take care what you see. You begin to look like what you look at. If we are to become like God, He must let himself be seen; deification depends on Incarnation.” p123 Footnote 65.