Jürgen Sarnowsky  

The De Sphaera of Johannes de Sacrobosco and its Commentators

At the Medieval and early modern universities, astronomy was studied in the context of the artes liberales, the seven liberal arts. Though during the 13th to 15th centuries the writings of Aristotle and namely his De Caelo were widely read and commentated upon, the basic text in astronomy was the small handbook entitled De sphaera of Johannes de Sacrobosco, probably an Englishman who taught at the University of Paris in the first half of the 13th-century. At many universities, reading of this text became obligatory and therefore many commentaries survive. One of the main topics of these was the discussion of the traditional geocentric system according to Ptolemy and Aristotle. Though the geocentric system was never really put into question and its consequences were regularly asserted, some doubts were also raised during the course of the discussion.

This paper will present some relevant excerpts from the sources, passages from the basic text of Sacrobosco as well as from some of the commentaries — literal or in the form of questions — from the period mentioned, concerning the question of the relationship between the Earth, the Sun and the planets. These excerpts are intended to give some insights into the teaching of cosmology at the scholastic universities.

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Jürgen Sarnowsky

Jürgen Sarnowsky has studied history, philosophy and physics at the Free University of Berlin. He completed his Ph.D. in 1985 on the commentary of Albert of Saxony on the Physics of Aristotle and his habilitation in 1992 on the Teutonic Knights in Prussia. He has been a professor of Medieval History at the University of Hamburg since 1996; his publications include books on the Hospitallers of Rhodes (Münster 2001) and England in the Middle Ages (Darmstadt 2002).