GIOVANNI di JANDUN. - Philosopher, born in Jandun, in the Ardennes, in the second half of the 13th century, died in Todi in 1328. He studied at the University of Paris, where, after obtaining his degree, he taught philosophy. On 13 November 1316, he was granted a canonry in the Chapter of Senlis by John XXII.
Against the Thomism dominant at that time, he rigorously upheld Averroist doctrines, particularly: the eternity of motion and of the world, the unity of the active intellect, the doctrine of double truth, and the impossibility of a rational demonstration of the immortality of the soul. Together with Marsilius of Padua, he collaborated on the Defensor pacis (a work in which, as is well known, the temporal-spiritual authority of the pope was harshly impugned, and, together with the principle of popular sovereignty, the supreme power of the emperor even in religious matters was affirmed), giving a philosophical imprint to the entire book. Giovanni’s collaboration on the Defensor pacis was so well known that he was included in the excommunication launched by John XXII on 23 October 1327 against the authors of the new heretical theory. But already in the preceding year they had sought and found refuge with Louis of Bavaria, of whom they soon became advisors. On 19 May 1328, Giovanni di Jandun was appointed by Louis the Bavarian as bishop of Ferrara, but death overtook him before he could reach his see. He was often confused with John of Ghent, so much so that certain works, such as the De laudibus Parisius and the Quaestiones, are indiscriminately attributed to one or the other.