Un vidimus mal interprété de Pierre de Vianden, prévôt de Saint-Martin de Liège, et de Conon, seigneur de Reuland (ca. 1264-ca. 1275

The work of editing medieval documents is full of pitfalls. Among the greatest difficulties is undoubtedly that of providing a critical edition of the copy of a document contained in a cartulary. What is the level of reliability of this copy with respect to its archetype? What is the role of the editor of the cartulary as mediator between the archetype and the copy? What should be done in the presence of an abbreviated copy of a lost archetype? In this paper, we offer a case study illustrating these issues, by focussing on a vidimus issued by Pierre de Vianden and Conon de Reuland at the end of the 1260s-early 1270s reporting an agreement between Count Philippe I of Vianden and Henri V of Luxembourg. Improperly dated and misinterpreted by researchers in the course of the 20th century, this document is the object of a new analysis which places it in a totally different historical perspective.