Alexander of Hales (Alexander Halensis, c. 1185–1245) was an English Franciscan theologian and master of the University of Paris, known as the Doctor Irrefragabilis ("Irrefragable Doctor"). After entering the Order of Friars Minor around 1236 as an established master, he transferred his chair in theology to the Franciscans, making him the first Franciscan regent master at Paris. He is credited with being the first scholastic to use Peter Lombard's Sentences as a textbook for systematic theology, and his lectures and disputations form the nucleus of the Summa Theologica (the Summa Halensis) — a massive synthesis assembled, after his death, by his Franciscan students and collaborators. The work exerted profound influence on Bonaventure and the early Franciscan school.
