Did Jesus really speak in the mystical manner portrayed in John 14?
I must say initially that I am not challenging Christian faith here. Christians believe that God used men to express divine truths in their own way so the narratives from Apostle John can be seen as just another way of conveying important truths.
But most of John 14 is rather a gabble. Christ constantly speaks of being IN the Father and the Father also being IN him. He is quite repetitious about it. He also however speaks of the disciples being in him and he being in them so an allusion to the Trinity doctrine cannot be read into it. If there were any doubt about that, verse 28 puts it as rest.
As far as we can tell Jesus was a popular preacher so it seems unlikely to me that he spoke in a gabble that would do a French philosopher proud. So it seems unlikely that John was trying to present the actual words of Jesus. My view is that he was trying to present very emphatically something that Jesus taught. And what that is is fairly clear. He was trying to emphasize a unity of belief and purpose between himself and the Father. He felt that he was so close to the Father that to see him was to see the Father.
So the passage is sensible enough if you allow for John's Gnostic way of writing. And from the opening verses of John's Gospel we have it made clear that John likes to present truths in that way.
Jesus also emphasises in the passage the importance of keeping his commandments -- so he was emphasizing the importance of his commandments by saying that they were also the commandments of the Father.
The major puzzle in chapter 14, it seems to me, is what we are to make of the Paraclete (helper) that Jesus will send when he is gone. Again I think we have to look for a figurative meaning rather than accept some sort of "Holy Ghost" story. And I think that the Paraclete must be the whole body of his teaching which will live on in the disciples. That Christian teachings can indeed be very sustaining, we now know. The way the Bible Students (Ernste Bibel Forscher) went to their deaths for refusing to bow the knee to Hitler is just one example of that strength.