In our last visit to John 1:1, we noted that all three clauses of the opening verse of the prologue (John 1:1-18) describe the absolute Deity of the Lord Jesus Christ. First, there is the eternal “ἦν” (“was”) of John 1:1a, which speaks to the eternal existence of the Logos Jesus Christ. As far back as one can think, the Logos “was” there and in essence, John 1:1a is proclaiming; “In the beginning was the eternal Logos.” Next, in John 1:1b, two persons are identified, the Word and the God and these two persons are said to be “πρὸς” (“with”) or together face to face with one another. And this “pros” was eternal (ἦν) according to 1:1b. Finally, there is John 1:1c, which is neither definite nor indefinite (regarding the use of Theos), but rather, qualitative. Meaning, John is telling the reader something about the Logos in 1:1c. He is not telling the reader that the Logos is τὸν θεόν, or, “the God,” as described in John 1:1b of the Father. To do such a thing would mix up the persons already described in 1:1b which would make the Logos the Father (aka Modalism). Also, John is not describing the Logos as a lesser, created little “g” god (aka Arianism). No Monotheistic Jew would speak or think in such a way. This point is obvious when one considers the constant use of “ἦν” (“was” – the imperfect form of “eimi”: c.f. John 8:58) in the text. John’s use of “was” implies in 1:1a that Jesus is eternal, in 1:1b that He has eternally been in intimate relationship with the Father, and, in 1:1c that He (the Logos) has eternally been fully Divine. Hence, the NET Bibles rendering of John 1:1c; “and the Word was fully God.”
James White addressed this very topic in his most recent episode of the “Dividing Line” (click HERE for the entire show) and did an excellent job in explaining all of the above information with great clarity. This information will be valuable to your apologetic and your faith. Also, Dr. White in the audio below mentions a number of times, his book, “The Forgotten Trinity” which can be found HERE. It is an excellent work that clarifies a great number of issues regarding the Triunity of YHWH.