Albert of Saxony and the argumentation for ten celestial orbs in the 14th century

Abstract

The subject of the present research is the work by Alberto of Saxony, a master at the Faculty of Arts of University of Paris, who discussed, in the middle of the 14th century, the number of orbs that would be in the cosmos. As a methodological approach, I chose rhetorical analysis of the sixth question of the second book in treatise Quaestiones subtilissime Alberti de saxonia in libros de celo et mundo, from c. 1351. During the 14th century, many scholars were concerned with commenting and explaining the Aristotelian works that had reached the Christian West during the precedent centuries. Among their inquiries, one was on the number of orbs in the cosmos, namely, the Aristotelian cosmos. The answers to this question provided during the Middle Ages depended on the movements the scholars attributed to the orb of the fixed stars. As one of them, Albert of Saxony, who also commented Aristotle’s De caelo et mundo, suggested that there were ten orbs, being two beyond the sphere of the fixed stars. To prove his idea, Albert used a rhetorical structure commonly found in scholarly works from this period, for rhetoric was fundamental for the construction of the quaestiones. He began his argumentation by mentioning ideas contrary to his and the arguments that supported them, to then put his own views forward. At this point, to support his thesis, Albert mentions Thabit ibn Qurra, a Harranite scholar from the 9th century, to whom it was attributed, during the Middle Ages, the discovery of a movement of the fixed stars called motus accessus et recessus. I argue that the presence of Thabit’s ideas in this quaestio might be explained as an auctoritas, i.e., textual authority, a resource frequently used in argumentative structures to reinforce or diminish a thesis. In consequence, the motu accesus et recessuss was used to explain the celestial structure advocated by Albert, as since he attributed another movement to the orb of the stars, extra orbs were justified. The present study analyzes Quaestio 6 as a way to clarify Alberto's argument for the ten celestial orbs, as well as his use of Thabit ibn Qurra’s ideas. Thus I hope to contribute to the studies on this work by Albert of Saxony and his role in the cosmology of the late Middle Ages.