The significance of church history

Writing about lost branches of the church, Philip Jenkins says in his The Lost History of Christianity:

In reality, Nestorians and Jacobites remained very influential for over eight hundred years after the great church councils expelled them from the imperial fold, and they attracted believers over a huge geographical area. To put that achievement in context, that time span is far longer than the entire history of Protestantism to date… .

When modern observers look at the course of Christianity, they often apply a kind of Darwinian perspective, assuming that some versions of the religion succeeded because they were better adapted to their circumstances than were others. From a theological standpoint, this would mean that some kinds of Christianity survived and flourished because they were more faithful, and truer to the divine plan. And the fact of survival in turn validates the present-day beliefs of Christians who follow those particular forms of the faith: faith interprets history, which supports faith. Yet such a model meshes poorly with the actual history of those other churches, which perished not through their own theological failures or contradictions, their own loss of faith, but through secular politics. In no sense were they less authentically Christian than the churches of Rome and Constantinople. If matters had developed differently, perhaps Christianity today would be thoroughly and “naturally” Asian and Nestorian, just as obviously and traditionally as we think of it as Euro-American. Neither faith, nor piety, nor scholarship, nor ancient tradition served to keep the churches alive across most of their ancient homelands, a great extinction that should offer a sobering message to modern-day believers. The success of a particular religion or faith tradition in gaining numbers and influence neither proves nor disproves its validity. (27-28)

A few thoughts:

1) Jenkins’ argument against the “theological” explanation he gives is facile; it assumes that history can only judge theological failure if a church fails because of its theology. But this seems to assume God can’t use violence to judge idolatry, as he did in the history of Israel, etc.
2) It also assumes a purely sociological way of determining what’s a Christian: if a group claims to be Christian and survives, it is Christian. This is perhaps useful from one point of view, but many Christians (including, e.g., Saint Paul) would disagree that it is ultimately sufficient.
3) On the negative side, I think most Christians would argue that scripture at least teaches that all true Christians will not be killed before the return of Christ. This gives a minuscule but real correlation between numbers and truth at the negative end (though, one should make room for the fact that “true” belief seems to be more about personal trust in Christ than necessarily being doctrinally pure, which might allow for some true Christians holding to false doctrine sometimes).
4) On the positive side, from my own more controverted point of view, I take a postmillennial view of history. This means that I think ultimately there will be some correlation between truth and numbers in terms of church growth.
5) However, I also think that this correlation may only be visible in retrospect; church history might look more like a sloppy upward spiral than a straight line. And indeed, it would be very difficult to falsify this kind of postmillennialism from the point of view of church history so far, since “dips” in numbers are only relevant to overall trajectory in proportion to the entire graph; but if we don’t know how long church history will be, we don’t know proportionately how much 2000 years is worth.
6) And in light of all this, I think Jenkins’ arguments are still instructive: I’m willing to read those lost Christianities charitably, and I think history is far more inscrutable than some high-church theologies suggest. We ought to recognize we really have little likelihood of accurately predicting what God will do with the church based on what God has done in history; we are safer when we ground statements about the future based on biblical promises.