We read the Gospels as “New Testament” even though they are about a time when the Gentiles and the Jews were two separate peoples (even if both were believers), the Temple is still central, the dietary and cleanliness laws are still enforced, and animal sacrifice is still practiced. What makes them “New Testament” is that they are written after the death and resurrection of Jesus. Even though they record the old world, they are written in the new world.
But I suspect there is one letter in “The New Testament” that was written in the old world by someone who did not completely know how the new world was about to be brought to birth.
In my opinion, James was written before Jesus died. This has nothing to do with any alleged problems with what James writes about justification and good deeds. (The fact he knows nothing about a Jew-Gentile issue in relation to justification is more relevant to my case). The smoking gun is this:
Name any other “New Testament” epistle that encourages believers to endure through suffering without mentioning the death and resurrection of Jesus as a past event that should give them encouragement and hope.
Beyond that, lets remember that the Gospels give us precious little information about what went on during Jesus three-year ministry. We know from the synoptics that Jesus sent out “missions” (a group of twelve and a group of seventy sent out in pairs) to preach throughout Israel. We lean in John’s Gospels that Jesus disciples baptized, that they had to flee from the Pharisaic persecution because they were baptizing, and that the religious leaders excommunicated those loyal to Jesus. The Gospels also show us groups in households where Jesus could go to teach and receive hospitality (such as the home of Lazarus, Mary, and Martha).
Wouldn’t people loyal to Jesus in different areas, who had received baptism from his representatives, meet regularly for prayer, Bible study, and mutual encouragement? Wouldn’t they invite fellow Jews to join them in the hopes of persuading them?
And could not those who had been cast out of the synagogue view themselves as “diaspora” even if they were geographically still in Israel?
I have toyed with this idea before. Recently, I listened to Jeff Meyers’ lectures on James where he argues that the author is James the son of Zebedee and for an early date. I found the lectures quite good (as well as personally convicting on some issues). But I just think the early date is earlier than he thinks. See also this.