Medieval Logic Diagrams

Abstract

This article describes the finding, documentation and significance of the set of medieval logic diagrams and associated text, all in highly abbreviated Latin minuscule, sketched on an inside wall of the Romanesque tower of the parish church in Bro, near Visby. The diagrams depict the Square of Opposition, the basic concept to be mastered in introductory logic as taught at medieval schools and universities. A date c.1200-1225 is suggested by their being executed in the earliest plaster when wet (tower built c.1200), while up to 1350 is suggested by palaeography. Dating by textual content is still in progress. Either way the Bro diagrams are among the earliest logic texts written in Scandinavia, and this is the first time for such texts to be found outside a manuscript. They are also the earliest known physical evidence of a teaching session or a discourse in logic. Furthermore they contribute to a growing body of evidence of the high standard of learning that existed in medieval Gotland.