Thanks to a grant of the Nordrhein-Westfälische Akademie der Wissenschaften und der Künste, Bielefeld University has started a fifteen-year project (2015–2030) that includes the production of a critical edition of Niklas Luhmann’s extant works and manuscripts, as well as the digitalization of his famous card index. This valuable enterprise has rekindled interest in what many scholars hold to be a ‘holy grail’: a marvelous instrument that aided great creativity and scientific production by the German sociologist. Indeed, people feel that looking inside the filing cabinet is like looking inside the mind of a genius at work. This article suggests a different point of view, rooted in the Enlightenment project of the sociologist of Bielefeld. The main hypothesis is that in the use of a card index as a surprise generator, there is nothing particularly surprising if one considers the evolution of knowledge management in early modern Europe. Rather, the question should be: how it is possible to explain the evolutionary improbability of the social use of ‘machines’ as secondary memories for knowledge management and reproduction? This article provides some suggestions for research and tries to determine where Luhmann’s card index comes from.