Peter Leithart wrote something earlier today that got me thinking. Leithart spoke of the begotten God/Word/Son exegeting God in John 1:18. The NRSV/ESV/NIV translate ἐξηγήσατο as “made him known” while the NET says “made God known.” The NLT says “revealed” while the KJV says “declared.” Compare the statement that “no one knows the Father except the Son and anyone to whom the Son chooses to reveal him” (Matt. 11:27). This points to preexistence in at least one of at least two ways.
First, one could argue that the LORD witnessed in the OT was the preincarnate Son since the Father was unknown prior to the Incarnation of the Son. There’s more than enough evidence in the NT use of the OT to suggest that the preincarnate Son was understood to be the LORD of the OT Scriptures. But this is the less preferable option (especially if one wishes to suggest that it is the Son alone who is witnessed in the OT). The more preferable option is to say that the Father was known in the OT, but that his Son/Word, who is close to the Father’s heart (John 1:18 NRSV) and who was with him in the beginning (John 1:1), was the one who made him known.