Pope from 1243. He was the most outstanding canon lawyer ever to become Pope, and he wrote a major commentary on the decretals, known as the ‘Apparatus’. Having tried unsuccessfully to resolve the dispute with Frederick II which he had inherited, at the Council of Lyons in 1245 he excommunicated and deposed him, and continued the struggle against his son. Under the pressure of financial needs he extended the system of provisions, and he authorized the use of torture by the Inquisition.
Subjects: Christianity — Medieval and Renaissance History (500 to 1500).