He recommended a couple of books on the subject by Alan Kreider, The Change of Conversion and the Origin of Christendom (Wipf & Stock Publishers: May 2007) and Worship and Evangelism in Pre-Christendom (Grove Books Ltd: September 1995). I found an article written by Kreider on line in which he quotes this:
Christians cannot be distinguished from the rest of the human race by country or language or customs. They do not live in cities of their own; they do not use a peculiar form of speech; they do not follow an eccentric manner of life . . . Yet, although they live in Greek and barbarian cities alike, as each one's lot has been cast, and follow the customs of the country in clothing and food and other matters of daily living, at the same time they give proof of the remarkable and admittedly extraordinary constitution of their own commonwealth. They live in their own countries, but only as resident aliens (paroikoi). They have a share in everything as citizens, and endure every thing as foreigners. Every foreign land is their fatherland, and yet for them every fatherland is a foreign land. They marry, like everyone else, and they beget children, but they do not cast out their offspring. They share their food with each other, but not their marriage bed . . . They love all people, and by all are persecuted. They are unknown, and still they are condemned; they are put to death, and yet they are brought to life. They are poor, and yet they make many rich . . . They are reviled, and yet they bless; when they are affronted, they still pay due respect . . . To put it simply: What the soul is in the body, that Christians are in the world. (Epistle to Diognetus, 5-6 (mid 2nd century))In other words, they're different.
In Resident Aliens: Life in the Christian Colony, Stanley Hauerwas and William Willimon say many of us have bent over so far to accommodate the ways of the world that we've fallen in. The church becomes more and more resident in the culture and less and less alien. We've got to get aliener.
Got to get our feet dirty: