Pastor Bob has asked me to take us to Chalcedon in terms of christology. I can certainly do this...but I don't want to bore my readers with the same subject for an extended period of time. I can cover all the controversies to Nicaea, Nicaea, and its fallout, but only if this is something that will interest you.
As for James McGrath's post today, arguing for a possession christology in John. I do not find these arguments convincing. There is no prophetic tradition from Judaism in which the prophet is ever God. No prophet would ever claim "I AM" for himself or "I and the Father are one." Now the Kavod and Angel of the Lord traditions do help to explain this, as they also help to explain the distinction that Jesus is the son and a mediator figure (which I have explained in earlier posts in this series). But prophet traditions do not. The spirit in prophetic tradition is always a temporary possession of a full human being and never makes the possessed God himself.
This is not to say that prophetic traditions have not influenced early strata of Johannine traditions. They have, particularly Samaritan understandings of the Prophet-like-Moses. But these traditions have been reconfigured within a Hellenistic model of anthropology in which the Logos descends into flesh. The language is not language of descent into a full human being, into a "man", but of the descent of God's Reason into flesh. This is ensoulment language not possession language.
Perhaps it would be helpful to know that in Hellenistic philosophy, particularly that influenced by Plato, God was conceived as The Good and The One. When he thinks (which is all he can do) he is Mind-Logos within which exists all thoughts and patterns for the universe. Plato perceived these to be "forms." Some of the first Christians thought of them as little logoi. Origen, in fact, says that these little logoi became our souls when their love for God began to cool off and they fell down into matter and became psyches. Only one little logos remained completely attached to God and this is what Origen thought became Jesus' soul.