Jean Mabillon's De re diplomatica, whose importance for diplomatics and the philosophy of history is well recognized, also contributed to the seventeenth-century European debate over the relationship among documents, archives, and historical or juridical proof. This article juxtaposes early works on diplomatics by Mabillon, Daniel Papebroche, and Barthélémy Germon against German ius archivi theorists including Rutger Ruland and Ahasver Fritsch to reveal two incommensurate approaches that emerged around 1700 for assessing the authority of written records. Diplomatics concentrated on comparing the material and textual features of individual documents to authentic specimens in order to separate the genuine from the spurious, whereas the ius archivi emphasized the publica fides (public faith) that documents derived from their placement in an authentic sovereign's archive. Diplomatics' emergence as a separate auxiliary science of history encouraged the erasure of archivality from the primary conditions of documentary assessment for historians, however, while the ius archivi's privileging of institutional over material criteria for authority foreshadowed European state practice and the evolution of archivistics into the twentieth century. This article investigates these competing discourses of evidence and their implications from the perspective of early modern archival practices.