In a message to the Masters of Oxford entitled On Wyclif, Pope Gregory XI condemns John Wyclif's criticism of church doctrine:
...it has come to our ears that John de Wyclif, rector of the church of Lutterworth, in the diocese of Lincoln, professor of the sacred scriptures (would that he were not also Master of Errors), has fallen into such a detestable madness that he does not hesitate to dogmatize and publicly preach, or rather vomit forth from the recesses of his breast certain propositions and conclusions which are erroneous and false. He has cast himself also into the depravity of preaching heretical dogmas which strive to subvert and weaken the state of of the whole Church and even secular polity, some of which doctrines, in changed terms, it is true, seem to express the perverse opinions and unlearned learning of Marsiglio of Padua of cursed memory, and of John of Jandun, whose book is extant, rejected and cursed by our predecessor, Pope John XXII, of happy memory. This he has done in the kingdom of England, lately glorious in its power and in the abundance of its resources, but more glorious still in the glistening piety of its faith, and in the distinction of its sacred learning; producing also many men illustrious for their exact knowledge of the holy scriptures, mature in the gravity of their character, conspicuous in devotion, defenders of the Catholic Church. He has polluted certain of the faithful of Christ by besprinkling them with these doctrines, and led them away from the right paths of the aforesaid faith to the brink of perdition.
Peters, Edward, Heresy and Authority in Medieval Europe. Phila.: U. Penn Press, 1980