Hilariously, the final chapter of this outstandingly dry and recitative book begins with the disclaimer that "the description that follows avoids strong theoretical assumptions."
It is, I believe, I little late for that advance knowledge.
At any rate, the question of the formation of early Christianity is the question of unity, among believers as well as their beliefs; one body believes in one Christ, one God. Christian monotheism is Judaic monotheism. This provided a ready contrast to the social diversity, complexity, and plurality of the broader Roman Empire.
Yet the point was not just that Christianity was internally united around a set of social symbols; it was unified over and against the outside world, bound with bonds of affection that would express precisely the honor of the one God. So that while Paul makes such abundant reference to the Jews, there is no mention of, or any evidence of, contact between the early churches and the Diaspora synagogues.
Of course, this was only a provisional separation; Pauline Christianity sought to bring absolutely everyone into the inner circle, hence their zeal for far-flung evangelism. And hence the need to refrain from some kinds of contact with the broader world, but never to fear contamination from it.
This over-and-against was only temporary because of the eschatological nature of early Christianity- Jesus' resurrection was not, for them, a timeless act for personal redemption, but the first act in the end of days which would judge everyone. The early Christians looked forward to a series of events in the immediate future that would transform every social relationship.
The early Christians were by their nature socially dissatisfied, and looked forward to the difference. They perceived their status in the eyes of the others to be less than it would ultimately be. They were the best living embodiments of cognitive dissonance.
So early Christianity invariably combined the traditional with the radically new. By so doing, it was able to move a fairly traditional culture- the broader Roman Empire- toward a radical world view and ethos without sacrificing continuity with the Empire's longer history.
Their eschatological vision both explained present circumstance and recommended a specific outlook and set of dispositions. It was given to them by Paul through a revelation of Jesus Christ. It defended the radically new in terms drawn from the old. The radically new was already attested to in ancient Scripture.
There is nothing new under the urban sun, even these radical claims about the end of days, even this assertion that He would also raise us, even our exaltation and enthronement. As Christ was first weak, then powerful, so too will weak and afflicted Christians be vindicated and glorious.
Thus early Christianity presented a picture of sons of light against suns of darkness, of spiritual powers at war with one another and with God- but pacified and reconciled by Christ's ascension through the astral spheres. Personal struggles of immorality, weakness, bondage, fear and suffering and even the tension between Jews and Gentiles accrue cosmic importance.
This eschatological background was disseminated by highly mobile leaders whose constant concern was unity. The local groups they formed were intimate and exclusive, with strong boundaries, commitment, and interpersonal engagement. They believed in a shift in the order of the world. A truly heterogeneous mix of people, they were weak in one or more terms of social power and status, but exhilarated by experiences of power in their meetings.
Early Christianity, then, and the central symbol of a crucified savior, did not so much prescribe individual expectations so much as it described what was happening to these ambiguously-statused people. The low were being, as it were, raised up.
That concludes this Cliff Notes series. Now get ready for the Qur'an.