Summary Boethius' De divisione or Liber divisionum was the authoritative book on mereology in medieval scholasticism. Together with other Boethian works it formed part of the Ars vetus, the core of which was constituted by Porphyry's Isagoge and Aristotle's Categories and Peri hermeneias, but after c. 1250 the Boethian works were but rarely taught in university. One master who did do courses on De divisione was Radulphus Brito (c. 1270 - 1320/21), who taught in the Parisian Faculty of Arts in the 1290's and possibly some years into the 1300's after having become a student of theology about 1299. Radulphus was an innovative thinker with a considerable impact on the philosophical debate in his lifetime, and he continued to be considered relevant till the end of the 15th century. He left a vast amount of writings, most of them from his days as a teacher of the arts. Among those preserved are quaestiones on the whole of the Ars vetus and Ars nova, Parva naturalia, Physics, De anima, Metaphysics and Ethics, as well as Priscianus minor. Radulphus taught some courses more than once, and each time revised the text of his lectures, leaving us with two or more versions of the relevant questions. On De divisione there are even two completely different sets of questions, both of which are edited for the first time in the present volume. The introduction contains a detailed study of the way Brito's question commentaries developed over time. TABLE OF CONTENTS Introduction to the edition of Radulphus Brito, Quaestiones supra librum Divisionum Boethii Introduction to Radulphus Brito, Quaest. Divis The work and Its Context Edition of Brito's Questions Edition Quaestiones supra Librum divisionum Boethii Br version S version