It is amazing how many times anti-Trinitarians quote only the last clause from John 1:1, as thought that is the whole verse.
Joh 1:1 In the beginning was the Word, and the Word was with God, and the Word was God. (ESV)
Looking at the first clause, "In the beginning" is clearly a reference to
Gen 1:1. The word "was" is the Greek,
en, which is a form of
eimi (I Am), and speaks of continuous action in the past, that is, absolute preexistence before any creation. What that statement means is that when the beginning began, the Word was
already in existence, and hence, there was never a time when he did not exist. The very same applies to the Father, who has absolute preexistence.
In the second clause, "and the Word was with God," it is the Greek
pros that is translated as "with." But it isn't merely speaking of being together or near. It expresses “direction towards,” as in relationship and communion, implying intimacy. It is important to note here that in the Greek the article is present, so it reads, "the Word was with [the] God." So, God is a reference to someone other than the Word, at a minimum it is a reference to the Father.
When it comes to the last clause, "the Word was God," it is significant that "God" doesn't have the article in the Greek, as it was in the preceding clause. If the article had been present then "Word" and "God" become interchangeable, and they are one and the same, which is the error of Oneness theology. But this whole passage is about the
logos, who the
logos is, not who God is, so John purposely doesn't use the article to avoid equating the two words. What it can only mean then, is that the Word was divine in nature, or deity. However, since there is only one God, it is rightly translated as "the Word was God."
There is only one understanding of this verse--the Word existed for eternity past in intimate relationship with another, who is God the Father (at a minimum), and the Word is divine in nature, making him also God.
We should also consider verses 2, 3, and 14:
Joh 1:2 He was in the beginning with God. (ESV)
We see a repeat of verse 1 with the use of
en,
pros, and God with the article, reaffirming the timeless preexistence of the Word who was in active communion with the Father.
Joh 1:3 All things were made through him, and without him was not any thing made that was made. (ESV)
Simple, straightforward logic tells us that since "all things were made through" the Word, and that "without him was not any thing made that was made," it necessarily follows that the Word is not something that was made (see also 1 Cor 8:6 and Col 1:16-17). That is, there never was a time when the Word did not exist.
John then makes it clear in verse 14 that "the Word became flesh and dwelt among us." That is, the Word,
not the Father, entered into time--Greek for "become" is
egeneto (same as "made" in verse 3)--and took on human flesh. This is all precisely what Paul is speaking of in Phil 2:5-8.
But, we should also consider John's reference to Gen 1:1 and note what else happens in that chapter.
Gen 1:1 In the beginning, God created the heavens and the earth.
...
Gen 1:26 Then God said, “Let
us make man in
our image, after
our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth.”
Gen 1:27 So God created man in
his own image,
in the image of God he created him; male and female
he created them. (ESV)
Clearly there is only one God. Interestingly, this one God uses plural personal pronouns of himself--"us" and "our"--to speak of creating humans. But when he actually does create man and woman, the pronouns become singular--"his" and "he." This, too, shows that there is plurality within the one God, so it is no surprise, indeed no coincidence, that John makes a reference to Gen 1:1 in John 1:1.
The incarnation is a mystery, but John clearly makes the case the Word had always existed before creation--absolute preexistence--
with God and was divine in nature. He then entered time, taking on human flesh, completed the work he both came and was sent to do, and then was received back into glory.
Remember, this is John's introduction, the whole point of which is to introduce us to the Word that became flesh for the salvation of humans and the redemption of all creation. Everything else he says about the Son, Jesus, the Son of God, flows from this and cannot contradict it.