As with the third sermon, Chrysostom offers little new in the form of argument in the fourth sermon in his series On the Incomprehensible Nature of God. In the first 10 paragraphs Chrysostom recapitulates the argument of the previous sermon. The final 19 paragraphs are a pastoral exhortation to attend carefully and reverently the service of the church. In the intervening paragraphs Chrysostom again attempts to advance the argument that the angels cannot comprehend God.
In sermon 4, Chrysostom returns from the speculative arguments in his previous sermon to more exegetically sound footing. He begins with thoughts on Ephesians 3:8-10:
To me, though I am the very least of all the saints, this grace was given, to preach to the Gentiles the unsearchable riches of Christ, and to bring to light for everyone what is the plan of the mystery hidden for ages in God who created all things, so that through the church the manifold wisdom of God might now be made known to the rulers and authorities in the heavenly places.
Again we see that an aspect of God is described as unknowable: his riches in Christ. And again the argument is pressed, “If the riches are unfathomable, how could he who gave the gift of the riches fail himself to be unfathomable?” (15). Beyond this, we see that God is using the church to teach the angels about his own wisdom. Therefore the same type of argument pursued so effectively in sermon 1 applies to angels as well: if they do not know the wisdom of God they “do not have a perfect comprehension of God’s essence” (13).
Unfortunately, this treatment is all too brief (11-16) for in the remaining chapters the preacher falls into the same errors as he did in the previous sermon. Paragraphs 17-31 are an exposition of John 1:18, “No one has ever seen God; the only God, who is at the Father’s side, he has made him known.” Chrysostom offers the standard explanation to harmonize this verse with those passages that speak of individuals “seeing” God: namely, that God manifested himself in an act of condescension without revealing his eternal essence. As in the previous sermon, when Chrysostom sticks to the intended referent of the text (i.e. man) he does well, but when he attempts to apply it to angels he goes off-track. In trying to argue so strongly for his position, he actually weakens it. The preacher would have been better served devoting more time to passages the clearly speak of the ignorance of angels (Eph. 3:10; 1 Peter 1:12); or on passages that speak of the exclusivity of God’s knowledge of himself.
Nevertheless, Chrysostom does offer some thought worthy commentary on the title, “only begotten Son.”
The name son belongs to men and it belongs to the Christ. But it belongs to us by analogy; it belongs to Christ in its proper sense. The title only begotten is his alone and belongs to no one else, even by analogy. Therefore, from the title which belongs to no one but to him alone you must understand that the title Son, which belongs to many, is his in its proper sense and meaning. This is why John first said, “only begotten,” and then, “Son.” (26)
While this series of sermons is identified as On the Incomprehensible Nature of God, the Anomoeans had more problems than the belief they could know God as God knows himself. They were Arians and so regarded Christ as less than God. Chrysostom will address this aspect of their heresy in later sermons, but he is already laying the groundwork for that.
Speaking of the Trinity is inherently dangerous, yet it is even more dangerous not to speak of it. Almost everything that can be said rightly about the Trinity can be taken the wrong way, or understood incorrectly. The most biblically accurate way we can speak of the Trinity is in the terms, “Father, Son, and Holy Spirit.” Yet there are potential pitfalls even here. If there is “Father” and “Son” there must be a time when the Son was not. If there is “Father” and “Son”, and “Holy Spirit” can we really consider the Spirit a person? Chrysostom begins to address this difficulty by reminding us of the true nature of the analogical language used of the Trinity.
When we speak of a son of a father we naturally understand that there was a time during which the father existed and the son did not. Until 1974, my father existed and I did not. The Arians took this analogically and applied it to the Trinitarian relationship of the Father and the Son: there was a time when the Son was not. But Chrysostom reminds us that they are reversing the analogy. Jesus is not the Son to the Father in all the ways that I am son to my father. Rather, I am son to my father in ways that Jesus is Son to his Father. I love my father, I trust my father, I seek to please my father, I have my father’s nature. These, and not procreation, are essential to the nature of “sonship.” If procreation were essential to sonship, we would not have adoption.
The use of “only begotten” simply reinforces this. “From this title you may believe that the common title of son is not common but is peculiar to him and belongs to no other as it does to him. Mysteriously, “only begotten” and “son” combine to teach us to put aside as untrue one of our certainties when consider the relation of the Father and the Son. If Jesus is the only Son of the Father, the Father and Son must both be eternal. If God is Father of only one Son, and if he is eternal, he must be eternally a Father of that Son. If the Son did not exist, neither would the Father. How is he Son? Because he is begotten. How is he without beginning? Because he is only begotten.
 All paragraph references refer to those in Paul W. Harkins, St John Chrysostom On the Incomprehensible Nature of God (Washington, D.C.: The Catholic University of America Press, 1984).