A young monk arrives at the monastery. He is assigned to helping the other monks in copying the old canons and laws of the church by hand. He notices, however, that all of the monks are copying from copies, not from the original manuscript.
So, the new monk goes to the head abbot to question this, pointing out that if someone made even a small error in the first copy, it would never be picked up. In fact, that error would be continued in all of the subsequent copies.