A comparison of the ideological composition of the Qumran library and Christian libraries from ancient Egypt, reconstructed from pre-Constantinian papyri, reveals a profound difference in the amount of group-specific material: ca. 28% Qumran “sectarian” at Qumran vs. ca. 60% “Christian” books in ancient Egyptian Christian libraries. Even for the second century, where we have much less data, the divide is quite great. If we take Qumran as example for a Jewish sectarian library, still focused largely on the Hebrew Bible and writings shared with other Jews, Christian libraries portray an independent group-specific identity, quite early on.