But someone might say: “I wish we had a test case where a published text of a NT papyrus manuscript was later supplemented by the publication of a fragment or two which gave total clarity on the beginnings and endings of lines and could help us with an assessment of what level of confidence we should have in reconstructed texts.”My provisional reply to the headline question would be Very Low.
The empirical test of the question described in this post yielded a surprising high score; nearly 50%. But it was of a biblical manuscript, in which the base text would have been more or less set. I would actually have expected the score to be higher, but the evaluation included word divisions, spelling, and punctuation. Such things often have a high rate of variation in ancient manuscripts.
The real test would be to revisit scholarly reconstructions of a fragmentary, otherwise unknown, nonbiblical ancient text after new fragments had been found which filled in some of the missing text. I expect the success rate would be well below 50%.
I know there have been cases where new fragments of a fragmentary (leather) text have been discovered; for example, Aramaic Levi and the Damascus Document. But I don't know if anyone has done a comparision of previous reconstructions after new material was found. If anyone knows of one, please drop me a note.
UPDATE (27 May): Reader Ounieh Carlson points to the Greek fragments of the Gospel of Thomas, which were discovered before the complete Coptic text was. "The reconstructions provided by scholars proved to be wildly off." A couple of links on the Greek Gospel of Thomas are here and here, but I don't have time right now to follow up the pre-Coptic reconstructions of the Greek.
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