Pope Benedict XVI and Pope Francis have each approached the papacy in strikingly different ways, yet they share the same fundamental vision of the world and man. In these pages, Cardinal Muller, Prefect of the Congregation for the Doctrine of the Faith, explores the differences and commonalities of these two popes, showing how the challenge for the Church's hierarchy remains the same, and how these two popes are leading the Church to resist worldly infections and to heal the spiritual diseases of our time. He also provides a succinct and fascinating look into the universal ministry of the Church, showing how the popes, as successors to Peter, are the visible head of the pilgrim Church and are tasked with carrying out the pastoral ministry of Christ. Cardinal Muller shows us that the popes are bound by the testimony of the Word of God in Scripture and tradition, and that when the Church liberates herself from worldly thinking the way is cleared for a spiritual renewal in Jesus Christ. With frank analysis of the challenges that societies and contemporary culture pose to the Church in light of the two pontificates, Cardinal Muller explores the proper role of the state and of the Church in secular society as well as the challenge for the Church hierarchy in resisting worldly infections and healing the spiritual diseases of our time. Working closely with both Benedict XVI and Pope Francis as a trusted member of the Roman Curia, Cardinal Muller offers us an inside look at the differences and similarities of the two men who have most recently been entrusted with the Chair of Peter.