11 Behold, in your mind, I see some two things, your memory and your thought, which is, as it were, the seeing faculty and the vision of your soul. You see something, and perceivest it by the eyes, and you commit it to the care of the memory. There, within, is that which you have committed to your memory, laid up in secret as in a storehouse, as in a treasury, as in a kind of secret chamber and inner cabinet. You think of something else, your attention is elsewhere; what you saw is in your memory, but not seen by you, because your thought is bent on another thing.
I prove this at once. I speak to you who know; I mention by name Carthage; all who know it have instantly seen Carthage within the mind. Are there as many Carthages as there are minds of you? You have all seen it by means of this name, by means of these syllables known to you, rushing forth from my mouth: your ears were touched; the sense of the soul was touched through the body, and the mind bent back from another object to this word, and saw Carthage. Was Carthage made there and then?
It was there already, but latent in the memory. Why was latent there? Because your mind was engaged on another matter; but when your thought turned back to that which was in the memory, thence it was shaped, and became a kind of vision of the mind. Before, there was not a vision, but there was memory; the vision was made by the turning back of thought to memory. Your memory, then, showed Carthage to your thought; and that which was in it before you directed your mind to the memory, it exhibited to the attention of your thought when turned upon it.
Behold, a showing is effected by the memory, and a vision is produced in thought; and no words passed between, no sign was given from the body: you neither nodded, nor wrote, nor uttered a sound; and yet thought saw what the memory showed. But both that which showed, and that to which it showed, are of the same substance. But yet, that your memory might have Carthage in it, the image was drawn in through the eyes, for you saw what you stored up in your memory. So have you seen the tree which you remember, so the mountain, the river; so the face of a friend, of an enemy, of father, mother, brother, sister, son, neighbor; so of letters written in a book, of the book itself; so of this church: all these you saw, and committed to your memory after they were seen; and did, as it were, lay up there what you might by thinking see at will, even when they should be absent from these eyes of the body.
Thou saw Carthage when you were at Carthage; your soul received the image by the eyes; this image was laid up in your memory; and you, the person who was present at Carthage, kept something within you which you might be able to see with yourself, even when you should not be there. All these things you received from without. What the Father shows to the Son, He does not receive from without: all comes to pass within, because there would be no creature at all without, unless the Father had made it by the Son.
Every creature was made by God; before it was made it was not in being. It was not therefore seen, after being made and retained in memory, that the Father might show it to the Son, as the memory might show to thought; but, on the contrary, the Father showed it to be made, the Son saw it to be made; and the Father made it by showing, because He made it by the Son seeing. And therefore we ought not to be surprised that it is said, “But what He sees the Father doing,” not showing.
For by this it is intimated that, with the Father, to do and to show is the same thing; that hence we may understand that He does all things by the Son seeing. Neither is that showing, nor that seeing, temporal. Forasmuch as all times are made by the Son, they could not certainly be shown to Him at any point of time to be made. But the Father's showing begets the Son's seeing, just in the same manner as the Father begets the Son. For the showing produces the seeing, not the seeing the showing.
And if we were able to look into this matter more purely and perfectly, perhaps we should find that the Father is not one thing, His showing another; nor the Son one thing, His seeing another. But if we have hardly apprehended this—if we have hardly been able to explain how the memory exhibits to the thought what it has received from without—how much less can we take in or explain how God the Father shows to the Son, what He has not from elsewhere, or that which is not other than Himself!
We are only little ones: I tell you what God is not, do not show you what God is. What shall we do, then, that we may apprehend what He is? Can ye do this by or through me? I say this to the little ones, both to you and to myself; there is by whom we can: we have just now sung, just now heard, “Cast your care upon the Lord, and He will nourish you.” The reason why you are not able, O man, is because you are a little one; being a little one, you must be nourished; being nourished, you will become full-grown; and what as a little one you could not, you shall see when full-grown; but that you may be nourished, “cast your care upon the Lord, and He will nourish you.”
Source: Tractates on the Gospel of John (New Advent)