A book, a pen, and the Sphere: Reading Sacrobosco in the Renaissance

This chapter attempts to provide a birds-eye view of the marginalia found in hundreds of copies and dozens of editions of Sphere by John of Sacrobosco. It first surveys the contents of the Sphere, its uses, and how it transformed during the period as a site for innovation in commentary and visual presentation. It then situates Sacrobosco within the university classroom by considering two readers: Alsatian humanist Beatus Rhenanus and Swiss Polymath Henricus Glareanus. It offers a preliminary sketch for a history of Sacrobosco’s renaissance readership—a readership chiefly of university students and masters, given the Sphere’s longstanding place in the university cursus. It shows that by deploying the swelling commentaries and visual apparatus of new print editions, readers of Sacrobosco more firmly embedded the Sphere’s cosmology into renaissance learning even as they linked the Sphere with newer disciplines such as cosmography. In the process, such apparatus discouraged high-level mathematical creativity, but also encouraged some readers to attend more to calculation.