How the obscure, marginal Jesus movement became the dominant religious force in the Western world in a few centuries.
OK, I'll confess that I never expected a sociologist to be a good literary stylist. Perhaps I'm just not well enough read in the field, but the others I've read have been mediocre at best. Rodney Stark is a sociologist turned historian who tries to use the analytical techniques of his field in history. His method is explicitly reductionist: can the rise of Christianity be understood non-miraculously?; or perhaps better ask can we understand the mechanism of the rise of Christianity?, ignoring the question of whether the mechanism was Divinely guided or not.
The book seems largely assembled from individual papers, each of which attempts to quantify growth rates and influences--and a number of his conclusions contradict the received wisdom.
The first chapter is dedicated to demonstrating that a growth rate of 40% (known to be achievable--see the Mormons) is adequate to explain the estimates of a majority of Christians in the Empire by 350 AD. Obviously the rate wouldn't be steady, and his initial estimates of the number of Christians conflicts with that in Acts. Mass conversions are not necessary to explain the growth, and known principles of networking (some of which he researched) can explain the conversion rate. His research studying Moonies and Moonies-to-be found that the group of Moonies converted friends, and not strangers; and the friends converted when their network of friends became predominantly Moonie. Converts were mainly "from the ranks of the religiously inactive and discontented and those affiliated with the most accommodated (worldly) religious communities." He demonstrates how these features pertain to the Roman Empire through the book.
He goes on to gleefully shred some of the sociologists who use metaphor as models ("Durkheim's 'discovery' that religion is society worshiping itself . . . How would one falsify that statement, or assertions to the effect that religion is a neurotic illusion or the poetry of the soul?")
In "The Class Basis of Early Christianity" he explains his distinction between a sect and a cult and their social differences. A sect is a schism in an existing "religious body when persons desiring a more otherworldly version of the faith break away to 'restore' the religion to a higher level of tension with its environment." A cult is a new faith (at least new in that society). Cults tend to attract better educated/upper class members dissatisfied with the existing religions. New age religions and offshoots are more common among the better educated than the less so. Sects tend to attract the less privileged. Examples: in a 1977 poll 17% of those with college experience were attracted to Zen, compared with 5% who had none; while 6% of those in college had been involved in faith healing while 11% of those with only grade school had been: cult vs sect. Early Christianity, though Roman officials at first thought it a sect of Judaism, was a cult in this sense of the word--a new religion. And lo and behold, Christianity seems to have attracted quite a number of high status converts, as he expects a cult to do.
Then he addresses "The Mission to the Jews: Why it Probably Succeeded." He compares the Hellenized Jews (the majority) and "God-Fearers" to the marginalized Jews of Europe who developed Reform Judaism. The Marcion affair indicates to him that Jewish Christianity was dominant in the middle of the second century. Marcion tried to simplify some issues with the Old and New Testaments by claiming that the Old Testament God wasn't the same as the New Testament's, so we should drop the Old and strip out OT references from the New. This is what you'd expect of a Gentile group, and the heresy was promptly stepped on; which is what you'd expect of a largely Jewish group.
I can't summarize easily his analysis of women in the church, and why it was a far more welcoming environment than the pagan world surrounding it. Suffice it to say that a baby girl in a Christian family was far more likely to survive than one born to a pagan Roman one. Some parts of this chapter need a strong stomach.
Go read the book. I have to give it back to the library, but The Rise of Christianity is now on my "Buy Myself A Copy" list.