Historians commonly designate the High Middle Ages as the era of the "papal monarchy," when the popes of Rome vied with secular rulers for spiritual and temporal supremacy. Indeed, in many ways the story of the papal monarchy encapsulates that of medieval Europe as often remembered: a time before the modern age, when religious authorities openly clashed with emperors, kings, and princes for political mastery of their world, claiming sovereignty over Christendom, the universal community of Christian kingdoms, churches, and peoples. At no point was this conflict more widespread and dramatic than during the papacies of Gregory IX (1227-1241) and Innocent IV (1243-1254). Their struggles with the Hohenstaufen Emperor Frederick II (1212-1250) echoed in the corridors of power and the court of public opinion, ranging from the battlefields of Italy to the streets of Jerusalem. In The Two Powers, Brett Edward Whalen has written a new history of this combative relationship between the thirteenth-century papacy and empire. Countering the dominant trend of modern historiography, which focuses on Frederick instead of the popes, he redirects our attention to the papal side of the historical equation. By doing so, Whalen highlights the ways in which Gregory and Innocent acted politically and publicly, realizing their priestly sovereignty through the networks of communication, performance, and documentary culture that lay at the unique disposal of the Apostolic See. Covering pivotal decades that included the last major crusades, the birth of the Inquisition, and the unexpected invasion of the Mongols, The Two Powers shows how Gregory and Innocent's battles with Frederick shaped the historical destiny of the thirteenth-century papacy and its role in the public realm of medieval Christendom.

Valla (1407-1457) was the most important theorist of the humanist movement. His most famous work is the present volume, an oration in which Valla uses new philological methods to attack the authenticity of the most important document justifying the papacy's claims to temporal rule.

Considered the paradigm case of the troubled interaction between science and religion, the conflict between Galileo and the Church continues to generate new research and lively debate. Richard J. Blackwell offers a fresh approach to the Galileo case, using as his primary focus the biblical and ecclesiastical issues that were the battleground for the celebrated confrontation. Blackwell's research in the Vatican manuscript collection and the Jesuit archives in Rome enables him to re-create a vivid picture of the trends and counter-trends that influenced leading Catholic thinkers of the period: the conservative reaction to the Reformation, the role of authority in biblical exegesis and in guarding orthodoxy from the inroads of "unbridled spirits," and the position taken by Cardinal Bellarmine and the Jesuits in attempting to weigh the discoveries of the new science in the context of traditional philosophy and theology. A centerpiece of Blackwell's investigation is his careful reading of the brief treatise Letter on the Motion of the Earth by Paolo Antonio Foscarini, a Carmelite scholar, arguing for the compatibility of the Copernican system with the Bible. Blackwell appends the first modern translation into English of this important and neglected document, which was placed on the Index of Forbidden Books in 1616. Though there were differing and competing theories of biblical interpretation advocated in Galileo's time—the legacy of the Council of Trent, the views of Cardinal Bellarmine, the most influential churchman of his time, and, finally, the claims of authority and obedience that weakened the abillity of Jesuit scientists to support the new science—all contributed to the eventual condemnation of Galileo in 1633. Blackwell argues convincingly that the maintenance of ecclesiastical authority, not the scientific issues themselves, led to that tragic trial.