This article examines the problem of canon-making in the Italian Renaissance. How did one store works to be read, how did one read them, and what did one exclude from a proper library: these concerns represent the general conceptual questions which the specifics of the article address. The article begins with a discussion of fifteenth-century library formation, then moves on to the specific case of Ferrara, using as a point of departure a dialogue set at the court of Leonello d'Este. The article presents an analysis of a section of that work on the constitution of a library, and then examines part 10. There, the interlocutors are concerned with authenticity, as they address how one determined whether a work was genuine or a forgery. Along the way, they offer literary and philological arguments, which, precisely because they are not in the front rank of humanist achievements, allow us to peer deeply into the social aspects of Renaissance reading practice. There is an edition and English translation of the text as an appendix.