1. =Peter d’Ailly=, professor and chancellor of the University of Paris, Bishop of Cambray in A.D. 1397 and cardinal in A.D. 1411, was one of the ablest members of the councils of Pisa and Constance. He died in A.D. 1425 as cardinal-legate in Germany. His chief dogmatic treatise, the _Quæstiones_ on the Sentences of the Lombard, occupies the standpoint of Occam. In many of his other works he falls back upon the position of the mystics of St. Victor (§ 102, 4), and recommends with much warmth the diligent study of the Scriptures. His ideas about church reform are centred in the affirmation of the Gallican Liberties, which he had to maintain as a French bishop, but are expressed with the moderation becoming a Roman cardinal. In opposition to Occam and the Spirituals, he founds the temporal sovereignty of the pope on the _Donatio Constantini_. He also holds by the primacy of the Roman bishop, as firmly established by Scripture. But the πέτρα of Matthew xvi. 18 he understands not of Peter, but of Christ. In this passage therefore no pre-eminence is given to Peter over the other apostles in the _potestas ordinis_, but by the injunction of John xx., “Feed My sheep,” such pre-eminence is given in the _potestas regiminis_. The œcumenical council, as representative of the whole church, stands superior to the pope as administrative head.