A few weeks ago, I found myself having a fruitful discussion about Christian unity with a nondenominational friend. His concerns echoed many of those voiced by Peter Leithart in The End of Protestantism—fragmentation over comparatively insignificant differences, the mandate of Jesus that his followers be one, and so forth. And I tend to think that many of those observations have force: in a cultural moment where questions of orthodoxy seem less and less bound up