The ancient Greek manuscripts of the New Testament, for example papyri 46, 66, and 75 from the second century write in capitals only, so one cannot determine it from those manuscripts.
Jesus addressed His Father as “The only true God” (John 17:3).
Then John 1:1 reads:
In the beginning was the Word, and the Word was with God, and the Word was God.
Virtually all translations (with the exception of the NWT) have a capital “G” in both instances of “God”. The first instance clearly refers to the Father, and the second to the Son.
John 1:1 does not teach that the Logos was God Himself.
How could the Logos be with God and also be God? That’s not what the text says.
The first “God” is prefixed with the article; thus “the God” (meaning the Father, whom Jesus addressed as “the only true God”.). The second “God” has no article. So it does not refer to the Father.
Because of the lack of an article, some think the sentence should read “and the Logos was a god”. This is also an incorrect translation.
That would be the case if the subjective completion had been placed AFTER the copula verb.
If John had meant “The Word was a god”, then the Greek words would have been:
ὁ…λογος…ἠν…θεος
the…word…was a…god
But this is not what John wrote.
If John had meant that the Word was God the Father Himself (as Modalists affirm), then the Greek words would have been:
ὁ…λογος…ἠν …ὁ…θεος
the…Word…was…the…God
Prefixing the word “θεος” with the article “ὁ” (with no other modifiers) would indicate that God the Father is meant. But that is not what John wrote.
Here is what John actually wrote:
θεος…ἠν… ὁ…λογος
God…was…the…Word
John placed the subjective completion BEFORE the copula verb! What did John mean? Did he mean that God the Father was the Word? No! If he had meant that, he would have prefixed the word “θεος” with the article “ὁ”. What then was his meaning? As a person who has studied Hellenistic Greek for several years and has even taught a self-devised beginner’s course to adults, I am going to propose a suggested translation, and then justify it by reference to other similar constructions in the New Testament.
A very crude translation could be “The Word was God-stuff”. However, this doesn’t sound very reverent. So I suggest “The Word was Divinity” or perhaps “The Word was divine”. He was divine because God begat Him before all ages as Another just like Himself! “God” or “Divinity” was the essence of the Word.
Let’s look at two more instances in the New Testament in which a subjective completion without a modifier is placed BEFORE a copula verb. In I John 4:8 and also in I John 4:16, we find the phrase:
ὁ…θεος… ἀγαπη…ἐστιν
the God…love…is
Here the subject is clearly the Father since the word “θεος” is prefixed with the article. But notice the subjective completion “ἀγαπη” occurs BEFORE the copula verb “ἐστιν”. The correct translation is: “God is love”. Love is the essence of God. This is analagous to saying in John 1:1 that Divinity is the essence of the Word.
One more example:
ὁ…λογος…ὁ…σος…ἀληθια…ἐστιν
the…word the [one]…of you reality…is
Translation: “Your word is reality”. God’s word is reality. There is never falsehood or unreality in what God says. Once again, the subjective completion “ἀληθια” comes BEFORE the copula verb “ἐστιν”. Reality is the essence of what God says.
Martin Luther, whatever else he may have been, had an excellent understanding of Greek. Concerning the phrase in John 1:1:
θεος…ἠν… ὁ…λογος
God…was…the…Word
Luther expressed quite succinctly what I have attempted to relate about the word order. He said:
“The lack of an article is against Sabellianism; the word order is against Arianism.”
Sabellianism was a form of Modalism, that God is a single divine Individual who expresses Himself in three modes: Father, Son, and Holy Spirit. Today, Modalism is represented by the United Pentecostal Church as well as the various sects of the “Apostolic Church”.
Arianism was and is thought by many to have been a position whereby the Son was a lesser god, and thus the translation “The word was a god”. This position is represented today by Jehovah’s Witnesses. The New World Translation actually renders the Greek phrase as "The word was a god.”
So I suggest the following translations as a good approximation of what the writer had in mind:
In the beginning was the Logos, and the Logos was with God, and the Logos was divine.
In the beginning was the Logos, and the Logos was with God, and the Logos was Deity.
So to answer your question as to how many Gods there are, there are exactly two Divine Individuals, God the Father and the Son of God. But in the sense of “True God”, there is but one.
As Paul wrote to the Corinthians:
For us there is one God, the Father, from whom are all things and for whom we exist, and one Lord, Jesus Christ, through whom are all things and through whom we exist. (1Corinthians 8:6)
In order to answer this question, I have to know what you mean by “co-eternal”. If by “eternal” you refer to time extending infinitely into the past (as well as the future), then I affirm that neither the Father or the Son are eternal. For I find an infinite regression of time into the past presents is incomprehensible as well as inherently contradictory. If you mean that they both exist/existed outside of time, then I affirm that the concept “outside of time”, has no meaning for me. If by “co-eternal” you mean that both the Father and the Son existed from the beginning of time and will continue to exist forever, then my answer is “Yes.”
My view is that the Father’s begetting of His Son marked the beginning of time, and that there was no “before”. For if B representes the beginning of time, and event E occurred before B, then B must not have been the beginning of time.
Jesus answered him, "If a man loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him. (John 14:23)
Jesus is at the right hand of his Father in heaven. So how do they make their home with the person who loves Jesus? They are able to extend their personalities anywhere in the universe, and especially in the hearts of the faithful. And that is the Holy Spirit—the very, living presence of the Father and the Son. They are so blended in every way, that they share the same Spirit. The Holy Spirit is not a third divine Individual, the rather the Persons of the Father and of the Son.
In talking to Trypho, a Jew, both Justin Martyr and he spoke of the Holy Spirit. Certainly Trypho wasn’t thinking of another divine Individual, since the Jews believe there is only one divine Individual. And it become apparent that Justin wasn’t thinking of the Spirit as another divine Indivudual either.
For in The Dialogue With Trypho, Justin asked Trypho, “Do you think that any other one is said to be worthy of worship and called Lord and God in the Scriptures, except the Maker of all, and Christ, who by so many Scriptures was proved to you to have become man?”
Trypho replied, “How can we admit this, when we have instituted so great an inquiry as to whether there is any other than the Father alone?”
Then Justin said, “I must ask you this also, that I may know whether or not you are of a different opinion from that which you admitted some time ago.”
Now if Justin had been a Trinitarian, this would have been the perfect moment to explain it. Instead of the answer he gave Trypho (stated immediately above), he would have said, "Well, I have introduced you to Christ as another one who can truly be called “God”. Now I want to tell you that the Holy Spirit is yet a third Person who is also called “God”. But he didn’t do that. If Justin had been a Trinitrian, he missed his opportunity.