“Thus, without explicitly intending to do so, Constantinople had fused religion with ethnicity within the Orthodox tradition—a particularly potent combination. Indeed, the richness of the Orthodox Churches lay in their cultural diversity even as they remained part of a broader, powerful Orthodox community united in common spiritual values, belief, and ritual. In sharp contrast, Islam strongly resisted the creation of any “ethnic” Islamic movements or use of local languages to replace Arabic for worship; but Islam also never adopted the highly centralized model of control that Rome did. Rome had a pope, Islam had a caliph, but the latter never remotely maintained the centralized position of religious power that the pope did.”