ESHS/HSS Annual Meeting

Controlling the Flow: Tabular Management of True Syzygy Computations in Paris (1320–1340)

• In Event: Tabular Practices and the Cross-cultural Exchange of Knowledge in Ancient in Medieval Astronomy 3

English Abstract

In this paper, resulting from a long term collaboration with Richard Kremer, I analyze the "computational scenarios" developed by a generation of Parisian astronomers—including John of Vimond, John of Lignères, and John of Murs—to solve the problem of true syzygy between 1320 and 1340. I argue that numerical tables function not merely as repositories of data, but as active tools that manage the "information flow" of astronomical procedures. By selecting specific quantities as argument and entry, these tables fundamentally restructure the mathematical path taken by the historical actor.
Using flowcharts to map procedural logic, I contrast the standard recursive methods available in the 14th century (derived from Ptolemy and Al-Battani) against the novel tabular solutions of the Parisian corpus. The analysis reveals two distinct paradigms of tabular innovation. The first, a "calendrical approach" (e.g., the Patefit), treats syzygy as a pursuit problem, utilizing lists to "black-box" geometric models. The second, a "mean motion and equation approach" (e.g., the Tabule permanentes), re-anchors the computation in model-related arguments, allowing for a deeper astronomical understanding of the time difference between mean and true syzygies. These tabular innovations did not merely speed up calculation; they disrupted traditional procedural flows and redefined which astronomical quantities were visible to the practitioner. Ultimately, these tables demonstrate that 'computation' is not a singular, neutral activity. Whether through the logic of the list or the logic of the equation, the table-maker by shaping different computational scenarios exerts control over the user's practice, defining not just how they calculate, but what they are able to see and understand about the cosmos.

Author

• Matthieu Husson