2 It goes on, “There was a man sent from God whose name was John.” Truly, brethren beloved, those things which were said before, were said regarding the ineffable divinity of Christ, and almost ineffably. For who shall comprehend “In the beginning was the Word, and the Word was with God”? And do not allow the name word to appear mean to you, through the habit of daily words, for it is added, “and the Word was God.” This Word is He of whom yesterday we spoke much; and I trust that God was present, and that even from only thus much speaking something reached your hearts.
“In the beginning was the Word.” He is the same, and is in the same manner; as He is, so He is always; He cannot be changed; that is, He is. This His name He spoke to His servant Moses: “I am that I am; and He that is has sent me.” Who then shall comprehend this when you see that all mortal things are variable; when you see that not only do bodies vary as to their qualities, by being born, by increasing, by becoming less, by dying, but that even souls themselves through the effect of various volitions are distended and divided; when you see that men can obtain wisdom if they apply themselves to its light and heat, and also lose wisdom if they remove themselves from it through some evil influence?
When, therefore, you see that all those things are variable, what is that which is, unless that which transcends all things which are so that they are not? Who then can receive this? Or who, in what manner soever he may have applied the strength of his mind to touch that which is, can reach to that which he may in any way have touched with his mind? It is as if one were to see his native land at a distance, and the sea intervening; he sees whither he would go, but he has not the means of going.
So we desire to arrive at that our stability where that which is, is, because this alone always is as it is: the sea of this world interrupts our course, even although already we see whither we go; for many do not even see whither they go. That there might be a way by which we could go, He has come from Him to whom we wished to go. And what has He done? He has appointed a tree by which we may cross the sea. For no one is able to cross the sea of this world, unless borne by the cross of Christ. Even he who is of weak eyesight sometimes embraces this cross; and he who does not see from afar whither he goes, let him not depart from it, and it will carry him over.
Source: Tractates on the Gospel of John (New Advent)