"From what I can tell and from what I've seen several scholars say, the Synoptic Gospels have a Christology in them that is less advanced than what we find in Paul's letters (especially the hymn in Philippians). If the Synoptics were written by members of a Pauline group sometime after Paul, how then do you explain them having a less advanced Christology?"That's really a complicated question, and it's not exactly an easy one to answer via a blog post. My newest book is Guía para entender a Pablo de Tarso: Una interpretación del pensamiento paulino (tr. Guide to Understanding Paul of Tarsus: An Interpretation of Pauline Thought), published by Editorial Trotta here in Spain. I gave Thomas a copy of it when he was here in Spain just a couple of weeks ago. I'm sure there will be plenty of interaction with this material as he works through it.
Let me just give a brief answer to the question above, as I'm sure others are curious as well. The Christology of Paul is very obscure, and in my opinion it's similar to what we find in the Book of the Parables of Enoch. There, the Messiah is a mere man and only the concept (such as what is said of him in the law of Moses) is pre-existent. Then, this concept becomes reality in a specific person. After the resurrection, he is exalted to the right hand of the Father and confirmed as Lord and Messiah–a work that is wrought by God, not the man.
In my book (mentioned above), I interpret the Christ hymn in Phil. 2:6-11 as a contrast between the first Adam and the second Adam. Jesus is the second Adam, but he is only exalted and placed almost to the level of God (Phil. 2:11) after his death. But Paul is totally a subordinationist in the way he thinks about all of this. (1 Cor. 15:24-28).
If so, Mark, who has an adoptionist Christology (i.e., Jesus is son of God by adoption at his baptism = Mark 1:9-11) can have a more advanced Christology than Paul. Also in Matthew and Luke (or the author of the supplementary pericopes in Matthew 1–2 and Luke 1–2) Jesus is considered divine from the moment he is born. Therefore, it is likely that this Christology is more advanced than Paul's.
But, in short, the Christology of the New Testament is a drawer of sastre. It is very diverse, dark, and complicated.
TWH: I had a wonderful time meeting with Antonio a couple of weeks ago. It is always a pleasure to spend time with him. My heartiest congratulations to him for the publication of this new book on Paul. I think there is lots for Pauline scholars to discuss. I'm looking forward to having some time to interact with some of the points he makes therein in the days ahead as time permits.
I think the first and primary issue deals with the the origins of the Gospels themselves. If one begins from the standpoint that the Synoptics are post-Paul (i.e., not written in his lifetime), problems ensue. This, of course, isn't the time or space to outline the best evidence in favor of the following composition order: first Matthew, then Luke, then Mark. But such is my position, and, by the way, it was the position held by almost all persons prior to the nineteenth century. All three of these works, in my opinion, were written during Paul's lifetime. Matthew, for example, was written shortly after Jesus' resurrection and was used as a discipleship resource and presentation of Jesus' identity as descendant of Abraham and David. Luke researched and wrote his the next Gospel in order to serve the churches where Paul had labored (as well as future ones that would be planted), which were primarily Gentile. It was not designed to replace Matthew, nor would it. Peter, the early church tells us, preached a series of messages in Rome. The Gospel of Mark is nothing more than the record of Peter's messages. All of this can be supported from both internal and external evidences.
The actual question that was presented to Antonio is rather interesting. I think it points out a little gap in the argument, though I can follow and understand the logic undergirding Antonio's position. I don't agree with it. But that's what makes this blog so special. If we are going to argue that there is a progression or development of theology in the New Testament corpus, how can a piece of literature have a regressed theology? That's the whole issue in the question. If you argue that the Gospels come later, i.e., after Paul, and those literary works are hailed as having a primitive Christian theology, how can you explain that? It's really a great question.
I actually do believe that there is a developmental nature in the letters of the New Testament. I don't think the theology was full-blown instantaneously. In other words, God revealed more and more about Jesus and his identity in the literature of the New Testament over time, the same as Jesus did over a three-year period during his life. Let me explain what that does not mean though. I'm not saying that the identity of Jesus morphed or changed. Matthew presents him as son of David and son of God (I don't hold to the position that Matthew 1–2, for example is an "addendum" or supplementary, rather it is original). God, through divine inspiration, continues to teach and reveal aspects of who Jesus is over time as the foundation of the church is being laid. While Matthew, Mark, and Luke say nothing of Jesus upholding the world, that actually is part of his identity. It is made known to us through inspiration as time proceeds in the compositional history of the NT corpus. He is the one through whom all things were created (John 1:3), just as he is the Father's powerful Word, by whom he upholds all that was created (Heb. 1:3). The New Testament is consistent in its theology; after all, its source is one and the same for all of its individual literary components, namely God.
As to whether or not an "adoptionistic" Christology best explains what it going on with the theology of the New Testament, I would argue that the starting point needs to be adjusted. I also do not think the New Testament teaches that Jesus was "adopted" as God's Son, but that he has always been, is, and always will be the eternal Son of God. Moreover, the origins of the Gospels themselves should be reconsidered based on better evidences. Beyond that, not a single Gospel or letter in the New Testament is designed to be exhaustive in its exploration into and exposition of Christian theology. Each work is situated in the historical context in which it was written.