From The World of Late Antiquity by Peter Brown, which covers roughly AD 150-750.
“The average Roman felt more strongly than previously that he stood alone and united against a threatening outside world.”
The significance of Christian community:
“The Christian Church differed from the other oriental cults, which it resembled in so many other ways, through its intolerance of the outside world. The cults were exclusive and, often, the jealously [sic] guarded preserve of foreigners [sic]; but they never set themselves up against the traditional religious observances of the society round them. They never enjoyed the publicity of intermittent persecution. While the oriental cults provided special means to salvation in the next world, the took the position of their devotees in this world for granted. The Christian church offered a way of living in this world. The skillful elaboration of the ecclesiastical hierarchy, the sense of belonging to a distinctive group with carefully prescribed habits and increasing resources heightened the impression that the Christian Church made on the uncertain generations of the third century. Seldom has a small minority played so successfully on the anxieties of society as did the Christians.”
“As a member of a church, the Christian could cut some of the more painful Gordian knots of social living. He could, for instance, become a radical cosmopolitan. His literature, his beliefs, his art and his jargon were extraordinarily uniform, whether he lived in Rome, Lyons, Carthage or Smyrna. The Christians were immigrants at heart…separated from their environment by a belief which they knew they shared with little groups all over the empire. At a time when so many local barriers were being painfully and obscurely eroded, the Christians had already taken the step of calling themselves a ‘non-nation.'”