The council of Constance, which revealed the eminence of Gerson, became in the end the cause of his downfall. He was the prosecutor in the case of Jean Petit, and the council, overawed by the duke of Burgundy, would not affirm the censure of the university and archbishop of Paris. Petit's justification of murder was declared to be only a moral and philosophical opinion, not of faith. The utmost length the council would go was to condemn one proposition, and even this censure was annulled by the new pope, Martin V., on a formal pretext. Gerson dared not return to France, where, in the disturbed state of the kingdom, the duke of Burgundy was in power. He lay hid for a time at Constance and then at Rattenberg in Tirol, where he wrote his famous book _De consolatione theologiae_. On returning to France he went to Lyons, where his brother was prior of the Celestines. It is said that he taught a school of boys and girls in Lyons, and that the only fee he exacted was to make the children promise to repeat the prayer, "Lord, have mercy on thy poor servant Gerson." His later years were spent in writing books of mystical devotion and hymns. He died at Lyons on the 12th of July 1429. Tradition declares that during his sojourn there he translated or adapted from the Latin a work upon eternal consolation, which afterwards became very famous under the title of _The Imitation of Christ_, and was attributed to Thomas à Kempis. It has, however, been proved beyond a doubt that the famous _Imitatio Christi_ was really written by Thomas, and not by John Gerson or the abbot Gerson.
The literature on Gerson is very abundant. See Dupin, _Gersoniana_, including _Vita Gersoni_, prefixed to the edition of Gerson's works in 5 vols, fol., from which quotations have here been made; Charles Schmidt, _Essai sur Jean Gerson, chancelier de l'Université de Paris_ (Strassburg, 1839); J. B. Schwab, _Johannes Gerson_ (Würzburg, 1859); H. Jadart, _Jean Gerson, son origine, son village natal et sa familie_ (Reims, 1882). On the relations between Gerson and D'Ailly see Paul Tschackert, _Peter von Ailli_ (Gotha, 1877). On Gerson's public life see also histories of the councils of Pisa and Constance, especially Herm. v. der Hardt, _Con. Constantiensis libri iv._ (1695-1699). The best editions of his works are those of Paris (3 vols., 1606) and Antwerp (5 vols., 1706). See also Ulysse Chevalier, _Répertoire des sources hist. Bio-bibliographie_ (Paris, 1905, &c.), s.v. "Gerson." (T. M. L.; X.)