Innkeepers inspired this dissertation. After working on ‘innkeepers’ as a topic for a research seminar paper, I soon discovered that the term caupo counted as an insult according to several church fathers, including Jerome. In the Contra Vigilantium, Jerome mocked his enemy, Vigilantius, by calling him a caupo who mixed water with wine; I wondered whether the title was true and the insult was deserved. What remained was to figure out who this man was and why he mattered. The dissertation is comprised of four parts: introductory chapters, a text with an en face translation, a philological/historical commentary, and an appendix. The first chapter introduces Vigilantius, discusses why a commentary of the Contra Vigilantium is needed, and provides a biography, supported by literary and historical evidence in response to the bolder and more fanciful account of W.S. Gilly.The second chapter treats Vigilantius as an exegete. From a sample of his exegesis preserved in Jerome’s Ep. 61, I determine that Jerome dismissed Vigilantius’ exegesis because he wanted to protect his own orthodoxy. The third chapter situates Vigilantius in the debate on relic worship. His position is valuable because he opposed most of his contemporaries, decrying relics instead of supporting their translation and veneration. The Latin text and format are taken from Jean-Louis Feiertag’s Corpus Christianorum Series Latina volume published in 2005.Verbatim citations of Vigilantius are fully capitalized and biblical citations are italicized. The present text is not a new critical edition, but aims to improve some of Feiertag’s editorial choices, which, although representative of the manuscript tradition, render the text more difficult to read. Each sentence of the Latin text is numbered and directs the reader to the corresponding sentence in the commentary. The commentary follows the model of the Gröningen commentaries on Apuleius.The text and translation are provided in smaller units and immediately precede the commentary for ease of reference. I also provide in the appendix a translation of Epp. 61 and 109, the text taken from Hilberg’s Corpus Scriptorum Ecclesiasticorum Latinorum edition, as it is referenced and commented upon at various points throughout the dissertation. Following the letters is a short discussion on the genre of the Contra Vigilantium.