GIOVANNI DI JANDUN. — Philosopher, born at Jandun, in the Ardennes, in the second half of the 13th century, died at Todi in 1328. He studied at the University of Paris, where, after obtaining his degree, he taught philosophy. On 13 November 1316 he received from Giovanni XXII a canonry in the Chapter of Senlis.
Against the Thomism dominant at that time, he upheld Averroistic doctrines with extreme rigor, particularly: the eternity of motion and of the world, the unity of the agent intellect, the double truth, and the impossibility of a rational demonstration of the immortality of the soul. Together with Marsilio da Padova he collaborated on the Defensor pacis (a work in which, as is well known, the temporal-spiritual authority of the pope was bitterly attacked, and, along with the principle of popular sovereignty, the supreme power of the emperor even in religious matters was affirmed), giving the entire book a philosophical imprint. G.’s collaboration on the Defensor pacis was so well known that he was included in the excommunication pronounced by Giovanni XXII on 23 October 1327 against the authors of the new heretical theory. But as early as the preceding year they had sought and found refuge with Ludovico di Baviera, whose advisers they soon became. On 1 May 1328 G. di J. was appointed bishop of Ferrara by Ludovico il Bavaro, but death overtook him before he could even reach his see. He was often confused with Giovanni di Gand, so much so that certain works, such as the De laudibus Parisius and the Quaestiones, are attributed indiscriminately to one or the other.