Saint Gregory the Great: The History of the Early Middle Ages' Most Influential Pope and the Rise of the Papal States

“No one does more harm in the Church than he who has the title or rank of holiness and acts perversely.”-St. Gregory the Great

The pope, the bishop of Rome, claims spiritual authority over more than a billion Catholics worldwide. He also exercises temporal authority over a tiny enclave of Rome consisting of the Vatican Palace, Saint Peter's Basilica, and 44 hectares with the ancient Leonine Walls. As Sovereign of the Vatican City States, he has around 1,000 subjects, mostly clerics.

While...