When a Oneness advocate on a Facebook group asked for trinitarians to explain how Jesus could be truly God, but be distinct from His Father, I replied with an exegesis of John 17:5. This verse clearly distinguishes the Son from the Father in Person but shows that they are coequal and coeternal.
Here is my explanation of the verse:
And now, O Father, glorify thou me with thine own self with the glory which I had with thee before the world was.
— John 17:5
“O Father” – This is in the vocative case, grammatically signifying that one person is addressing another person. In the Koine period the vocative case was passing from common use and you see nominatives in many places where a vocative would function, such as when Thomas addresses Jesus with a compound nominative in John 20:28.
“glorify me” – This is Jesus, after having addressed the Father with a vocative, issues an imperative to “glorify” (doxason) him. See Isa 42:8 where Yahweh will not give His divine glory to another. If Jesus is Yahweh, this, of course, works. Also, grammatically you have one person addressing another with a vocative and an imperative. Yahweh is one Being Who is three Persons.
“with thine own self” (para seautou) – Jesus asks the Father to glorify Him “by the side of” Himself. They, as distinct Persons as the pronouns, cases, and moods indicate, are to be glorified together with the Son “at the side of” the Father.
“with the glory which I had with thee” – Again, the two pronouns in this clause (“I” and “thee”) in any expression of language indicates one person speaking to another person. The Son is asking the Father to restore glory (“which I had“). If the Son were an “idealized plan” and not a person when He formerly had this glory, these words would not make sense. “I” once again cannot be anything other than a Person. Idealized plans do not speak! “With thee” (para soi) indicates a conscious and distinct experience. The Son is personally with the Father at this former time, not in His mind!
“before the world was” – The Son, then, AS the Son–as a Person–possesed this glory formerly with the Father before creation. This means that the Son is eternal just as the Father is eternal. When the Son is said to have created all things (Joh 1:3; Heb 1:2; Col 1:16; 1Co 8:6), the Son as the Son really did create all things. The Father, Son, and Holy Spirit as the persons of the One God Yahweh all shared the divine glory in eternity before creation.
John 17:5 will always be a thorn in the side of the fantasies of the Oneness position.