A common dilemma in interpreting manuscripts is the degree to which the editor should preserve odd or seemingly ungrammatical readings simply because that is how the text appears in the manuscript. In this article Shipley uses a parent and child manuscript of Livy to show how and why errors come into texts as they are copied and to suggest methods for recognizing such errors and correcting them without over correcting and thereby contributing to further corruption of the lost original text. This is a useful piece for illustrating the process of taking a text from manuscripts to edition and also for illuminating the hidden uncertainty in all surviving classical literature.