I (Ben) noted last week about Justin Martyr’s very clear affirmation that Jesus eternally existed and became incarnate in time in his Dialogue with Trypho Chapter 48. In the conclusion I noted the issue of distinguishing between economy (what God does) and ontology (how God is). The economy is clear in that statement, but what about ontology. Trypho has the same question!
Chapter 50: “You seem,” said Trypho, “to have debated with many persons on every possible topic, and consequently are ready to answer any of my questions. Tell me then, first of all, how can you prove that there is another God besides the Creator of the world, and then show that He condescended to be born of a virgin.”
Justin continues a previous argument (about the two advents of Christ) before coming back to this question in chapter 55ff. In chapter 56, Justin provides a lengthy set of quotations and descriptions of the Abraham’s interchange with three men and Lot’s later interchange. His argument is basically that God is present in two places at the same time. Summing up at key points, he writes:
Chapter 56: “Then,” I said, “let us return to the Scriptures and I will try to convince you that He who is said to have appeared to Abraham, Jacob, and Moses, and is called God, is distinct from God, the Creator; distinct, that is, in number, but not in mind. For I state that He never did or said anything else than what the Creator — above whom there is no other God — desired that He do or say.” …
 At this point I asked, “Do you not see, my friends, that one of the three, who is both God and Lord, and ministers to Him who is in Heaven, is Lord of the two angels? When they went on to Sodom, He stayed behind and talked with Abraham, as Moses testified. Then He went His way after His conversation, and Abraham returned to his place.  And when He came to Sodom, it was no longer the two angels, but He Himself, who talked with Lot, as is evident from the Scriptures. He, indeed, is the Lord who was commissioned by the Lord in Heaven, that is, the Creator of all things, to inflict those dreadful punishments upon Sodom and Gomorrah, which are described in the Scriptures in this fashion: ‘The Lord rained upon Sodom and Gomorrah brimstone and fire from the Lord out of Heaven’ [Gen 19.24].”
He goes on to include discussion of the burning bush and gives this description:
Chapter 61 “So, my friends,” I said, “I will now show from the Scriptures that God has begotten of Himself a certain rational Power as a Beginning before all other creatures. The Holy Spirit indicates this Power by various titles, sometimes the Glory of the Lord, at other times Son, or Wisdom, or Angel, or God, or Lord, or Word. He even called Himself Commander-in-chief when He appeared in human guise to Jesus, the son of Nave. Indeed, He can justly lay claim to all these titles from the fact both that He performs the Father’s will and that He was begotten by an act of the Father’s will.  But, does not something similar happen also with us humans? When we utter a word, it can be said that we beget the word, but not by cutting it off, in the sense that our power of uttering words would thereby be diminished. We can observe a similar example in nature when one fire kindles another, without losing anything, but remaining the same; yet the enkindled fire seems to exist of itself and to shine without lessening the brilliancy of the first fire. My statements will now be confirmed by none other than the Word of Wisdom, who is this God begotten from the Universal Father, and who is the Word and Wisdom and Power and Glory of Him who begot Him.
This doesn’t sort all the questions about ontology by any means, but it shows that Justin was indeed aware of the issues. Though later argumentation is framed differently, the ideas of God meeting Abraham in Genesis 19 which is so central for Justin is at the heart of Rublev’s Trinity:
As Brevard Childs and Kavin Rowe argued so well: the OT is not an impediment to the Trinity, it is the necessary foundation on which the Trinity is grounded.