The figure of Antichrist has gripped the Christian imagination for two thousand years. But Antichrist does not spring fully from the pages of Scripture. Rather, he emerges over a millennium of reflection on hints and clues scattered throughout Scripture and Christian tradition. In particular, the image of Antichrist is tied in a vital way to the man medieval Christians knew simply as 'the Apostle' - St. Paul. Constructing Antichrist engages readers with the question: what does Paul have to do with the Antichrist? Integrating new scholarship in apocalypticism and the history of exegesis, this book is the first longitudinal study of the role of Paul in apocalyptic thought. Readers will gain new appreciation for the theological weight of medieval exegesis generally and for the persistence of apocalypticism in the medieval Christian imagination as it dared to envision the Adversary. The author argues that the western doctrines of Antichrist and the Last Days are entwined with the development of medieval New Testament exegesis. The Second Letter to the Thessalonians - a brief and much-debated apocalyptic text in the New Testament - is the most important locus for doctrinal speculation about Antichrist and the coming End. The author carefully examines commentaries on 2 Thessalonians from the fourth to the twelfth centuries and finds that they provide the 'architecture' for the developing doctrine of Antichrist as it is portrayed in later medieval art and literature. By the twelfth century, this tradition of reflection distills from the various early interpretations a classic, synthetic understanding of Antichrist and the End that forms an authoritative consensus for centuries.