Cultures and subcultures both can be tight or loose. At the extreme end of the tight scale we have small communities in lockstep, agreeing on virtually everything. At the extreme end of loose, we have cosmopolitan cultures with the only thing in common being the fact that everyone is in the same place at the same time, having very little in common. Tight cultures are not interested in proselytizing really, because converts just track things in. Loose cultures develop a radical live-and-let-live mentality, which devolves into an individualist autonomy.
When a Christian church is functioning as it ought to function—declaring the whole counsel of God, worshiping together, sharing community, and so on—the end result is going to look a lot like a tight community. The trick is to develop the bonds of koinonia community, such that it rivals the Amish or Hasidic Jews, but while at the same time maintaining a radical openness to newcomers.
The temptation, once you have the good thing going, is to become ingrown. You don’t want to welcome newcomers, because they don’t know all the unspoken expectations, and they track things in. When your house is clean and tidy, and people come in from the rainy and muddy outdoors, it messes things up.
Many modern churches, reacting away from this, have wanted to celebrate diversity for its own sake. But the Bible requires us, in multiple places, to cultivate like-mindedness. “Fulfil ye my joy, that ye be like-minded, having the same love, being of one accord, of one mind” (Phil. 2:2).
If we may use the illustration of a college dedicated to a biblical worldview, we shouldn’t mind that the freshmen come in thinking all sorts of things. But if the graduates are going out the same way, there is a problem. But many colleges flip this around. Because of their history or denominational affiliation, the freshmen are relatively homogenous, but the alums are not. This is our actual problem. The Bible tells us to strive for like-mindedness, and we strive for the opposite.
And so with a church community, because of evangelism and because of refugees from the wider Christian world, we should be constantly welcoming a very diverse “freshman class.” But we do so because we are engaged in culture-building, which is not an smorgasbord affair. No, we sit down together, family style.