I started James D.G. Dunn’s 1980 book, Christology in the Making: A New Testament Inquiry Into the Origins of the Doctrine of the Incarnation. Dunn is looking for the origins of the doctrine of the incarnation, the notion that God became flesh in the person of Jesus.
Dunn does not think that the doctrine of the incarnation originated with Paul because Paul in Romans 1:4 says that Jesus was designated to be the Son of God at his resurrection, which (for Dunn) means that Paul thought Jesus became Son of God at that time. This sort of message also appears in Acts, Dunn maintains. Dunn does not appear to believe that Paul thought Jesus was pre-existent. In my reading so far, Dunn does not interact with Philippians 2:5-11 and II Corinthians 8:9, passages that seem to support the notion that Jesus was a pre-existent being who became human, but Dunn may do so later in the book. Dunn does, however, address Galatians 4:4 (which says that Jesus was made of a woman) and Romans 8:3 (which says that God sent his Son in the likeness of sinful flesh), but Dunn does not think these passages support pre-existence, but rather highlight that the Savior has a solidarity with human beings as he redeems them from their condition: like human beings, Jesus was made of a woman and under the law and has the likeness of sinful flesh.
Dunn does not think that the doctrine of the incarnation originated with the Gospel of Mark or the Gospel of Matthew, either. Neither talks about Jesus’ pre-existence, according to Dunn, and each presents Jesus as becoming the Son of God at different points: Mark depicts it as occurring at Jesus’ baptism, and Matthew at Jesus’ birth to a virgin. Dunn does not believe that passages about Jesus coming or being sent relate to a notion that Jesus pre-existed. Rather, Dunn argues, prophets (and others) came and were sent by God for certain purposes, without being pre-existent, and that’s what is occurring with Jesus when he came or was sent (see here for a response to that sort of argument). Dunn also does not think that the title “Son of Man” indicates that Jesus was believed in Mark and Matthew to be pre-existent, for the notion that the Son of Man is a heavenly Messiah is in the Similitudes of Enoch, which Dunn believes came after the synoptic Gospels because it appears to interact with them, in some manner.
Dunn believes that Hebrews moves a little in the direction of Jesus being pre-existent. Dunn does not think it’s a full-fledged concept in Hebrews, however, but rather that Hebrews is drawing from Platonism. Dunn also argues that Hebrews, in addition to employing Platonist ideas, sometimes depicts Jesus as becoming the Son of God at his resurrection. Dunn is open to the notion that what we see in Hebrews is an idealized pre-existence, the idea that Jesus pre-existed in the sense that he was in the thoughts and plans of God from the beginning, not in the sense that he was an actual pre-existent being. But Dunn settles on the idea that Hebrews depicts Jesus as actually pre-existent. (UPDATE: Dunn later in the book appears to backtrack from this position.)
For Dunn, the Johannine writings have more of a concept of Jesus’ pre-existence. But, as Dunn notes, John was late. And, because such a concept does not appear in Paul, Mark, and Matthew, Dunn believes that it is a result of John’s reflections on the significance of Jesus, rather than something that goes back to Jesus himself. (UPDATE: Later in the book, Dunn says that John 1 may be using an earlier hymn. Dunn also appears to argue that I John does not support Christ’s pre-existence, but was somewhat of a transition to that view.) Regarding Jesus’ own Christology, Dunn appears to think that Jesus thought his relationship with God was special, but Dunn does not seem to believe that Jesus saw himself as God incarnate.
This was essentially the model of Christological development that I got at DePauw University. So why read Dunn, if I’ve already encountered his concepts before? Well, he does have a good discussion about the idea of the Son of God in the Greco-Roman world, as people claimed to be divine, and yet Celsus dogmatically proclaimed that “no god or son of god either came or will come down to earth” (Origen, Contra Celsum V.2). There are also other interesting side-discussions.