A common proof-text for the notion that early Christians believed Jesus is God, and so in favor theologies such as trinitarianism or modalism, is John 10.30.
‘The Father and I are one.’
However, despite the popularity of the ‘priestly prayer’ in John 14–17, its verbal and conceptual echoes to earlier parts of the gospel are frequently overlooked. Near the end of the prayer, Jesus states that he is addressing it to ‘the only true God’, who is identified as ‘the Father’ and specifically not ‘Jesus the Messiah, whom you have sent’ (17.1–3). As in the rest of the New Testament, ‘God’ is exclusively ‘the Father’. In this prayer, Jesus implores:
John 17.11
‘Holy Father, protect them in your name that you have given me, so that they may be one, as we are one.’
He later provides some definition for this oneness:
John 17.23
‘I in them and you in me, that they may become completely one’
This echoes another statement Jesus made in chapter 10, just a few sentences after his initial declaration of oneness with God.
John 10.38
‘the Father is in me and I am in the Father.’
The prayer in John 17 expresses a desire for Jesus’ followers to be ‘one’ in the very same way ‘as’ Jesus and God. Rather than concerning any sort of ontological equivalence, the simpler interpretation is that Jesus wants his followers unified with one another through harmony. This is how Jesus and God are ‘one’. Elsewhere in the gospel, the author demonstrates what this oneness looks like, that Jesus became one with God by harmonizing with God’s will, so that he can do nothing unless God directs him to.
John 5.19, 30
Jesus said to them, ‘Very truly, I tell you, the son can do nothing on his own but only what he sees the Father doing, for whatever that one does, the son does likewise. … I can do nothing on my own. As I hear, I judge, and my judgment is just because I seek to do not my own will but the will of him who sent me.’
John 8.28
So Jesus said, ‘When you have lifted up the son of man, then you will realize that I am he and that I do nothing on my own, but I speak these things as the Father instructed me.’
And Jesus likewise wants Christians to do the same, also expressed in the ‘priestly prayer’.
John 15.5
‘I am the vine. You are the branches. Those who abide in me and I in them bear much fruit, because apart from me you can do nothing.’
As Jesus has harmonized himself to God, his followers must harmonize themselves to each other and to Jesus. In fact, the author seems to have anticipated Jesus’ words in John 10.30 would be misinterpreted as him claiming to be God, which the author refutes in the dialogue which immediately ensues. Jesus’ opponents charge him with
John 10.33
‘blasphemy, because you, though only a man, are making yourself God.’
In his response, Jesus expressly denies having ever identified himself as God, but only as God’s son.
John 10.34–36
Jesus answered, ‘Is it not written in your law, “I said, you are gods”? If those to whom the word of God came were called gods—and the scripture cannot be annulled—can you say that the one whom the Father has sanctified and sent into the world is blaspheming because I said I am God’s son?’