This edition has had a long genesis. Jeanne Bignami Odier, the author of two important studies of Jean de Roquetaillade published in 1952 and 1981, planned an edition of the Liber ostensor, a massive undertaking which she was unable to complete. The present volume is based on her preliminary work and is the result of a collaboration involving the three editors, André Vauchez, Clémence Thévenaz Modestin and Christine Morerod-Fattebert, together with no fewer than twenty-one contributors of commentaries and notes. At first sight it might seem strange to expend such energies on a work, surviving only in the author's autograph manuscript, of an eccentric friar who spent most of his life from 1344 onwards in Franciscan and papal prisons and who was regarded by some as insane. However, Jean de Roquetaillade (Iohannes de Rupescissa) and his Liber ostensor are much more than peripheral curiosities. Situated firmly in a tradition of prophetic writing, Jean was an influential figure. He was consulted by cardinals, and he was in close contact with Cardinal Elie Talleyrand de Périgord, protector of the Franciscan order and dedicatee of the Liber ostensor. Apostolic poverty, the Spiritual Franciscans and other controversies involving the order feature prominently, while there are many allusions to political events, above all in the kingdom of Naples, where Talleyrand was allied to the house of Durazzo. The work's prediction of the imminent coming of two AntiChrists and of the reparator, a Franciscan pope who would revive the Church, did not make it any less topical. The Liber ostensor is divided into twelve treatises, the ninth of which is largely autobiographical. This treatise and other sections of the work throw light on the papal court at Avignon, not least the prison of the auditor of the apostolic chamber, where the Liber ostensor was written (between May and September 1356). The great merit of the present edition is not only to have reproduced the full text of the Liber ostensor but also painstakingly to have explained the numerous allusions to personalities and events and the use of a large body of prophetic literature. The volume begins with a clear account of the life and copious writings of Jean de Roquetaillade (pp. 1–62) and a summary of the contents of the Liber ostensor (pp. 63–97). Of particular value is the appendix describing the prophetic sources used by Jean, which include Ps.-Joachimite works, Arnold of Villanova, Robert of Uzès, Hildegard of Bingen (in Gebeno's compilation) and many other texts (pp. 865–956). With the publication of the Liber secretorum eventuum by R. E. Lerner and C. Morerod-Fattebert in 1994, and of the present edition, we at last have the materials at our disposal to seek to assess the place of Jean de Roquetaillade in the currents of fourteenth-century religious thought.