Many students go through their entire undergraduate careers without ever looking down to the bottom of a critical text at the apparatus criticus. Yet a reading of a text which does not take the apparatus into account gives too much authority to the text, treating it as a single work by a single author. In reality the transmission of manuscripts renders works that were originally by a single person into texts by multiple authors, from multiple sources. Since I have started using apparatus critici in my own reading, I now see ancient texts as unstable works. This paper is an exercise in using an apparatus criticus. I have chosen a page out of Livy's Ab Urbe Condita, which contains discrepancies of various types, outlined in the apparatus criticus. I dissect the apparatus criticus, applying it to the text above and following what I find to secondary resources, including commentaries and unabridged dictionaries. I investigate the classical scholars whose names appear within the apparatus. Through my analysis of the apparatus criticus, I show how an unstable text requires active and close reading, which means making choices through an informed comparison of the alternatives provided by discrepancies. When approached from the right perspective, these discrepancies can be windows to discovery. Unstable texts, when looked at with fresh eyes, may yield surprising new results. This is only possible when young scholars learn to use the apparatus criticus.