Brett Edward Whalen works on Christian intellectual and cultural history during the European Middle Ages, mainly focusing on the eleventh through the thirteenth centuries. He has published works on the crusades, apocalypticism, pilgrimage, and the medieval papacy. His most recent book, The Two Powers: The Papacy, the Empire, and the Struggle for Sovereignty in the Thirteenth Century (University of Pennsylvania Press, 2019), reappraises the epoch-making clashes between two popes, Gregory IX and Innocent IV, and the Hohenstaufen emperor, Frederick II. He has published articles in journals including The American Historical Review, Traditio, and Viator. Whalen also serves as the series editor for Trivent publishing’s new book series The Papacy and Medieval Christendom: Critical Perspectives. He is currently in the early stages of a research for a new book, Medieval Jesus: The Son of God from the Middle Ages to the Present.