Dirck van Bleyswijck's Beschryvinge der stadt Delft presents an ambiguous and problematic attitude to the medieval history of Delft, which makes it interesting to scholars wishing to explore the perception of the Middle Ages as it crystallized during the early modern period. The aim of this contribution is to determine the intellectual origins of Van Bleyswijck's work as a historian in the context of his perception of the medieval past. The analysis of Van Bleyswijck's performance as a historian is based on a case study derived from the narrative: quotations from source texts and commentary about the life of the medieval Delft beguine Geertruyd van Oosten will be compared. Van Bleyswijck's representation of the Middle Ages was formed by a combination of humanist and proto-Enlightenment concepts, which entailed a critical reaction to forms of religious culture known to medieval society.