[7] He was an early infallibilist;[8] the concept of papal infallibility is thought to occur first in a work he wrote concerning the conflict of Pope John XXII (1316–34) and the Franciscan Spirituals.
Xiberta, the Carmelite scholar who edited [Terreni's] work, 'if he had written it after Vatican I he would have to add or change hardly a single word.
"[14] He was one of those opposing the views of Arnold of Villanova on the Antichrist;[15][16] and he first dubbed Joachim of Fiore a heretic.
[17] He was asked, with Pierre de la Palud, to report on Peter John Olivi's apocalyptic writing.
Other works include the Errores Sarracenorum against Islam,[20] a Summa de haresibus and a Decretum commentary.