Albert of Brudzewo's Little Commentary on George Peurbach's ‘Theoricae Novae Planetarum’

1. IntroductionAlbert of Brudzewo (c. 1445-95) was the most influential astronomer at the Jagiellonian University in Cracow when Nicholas Copernicus began the serious study of astronomy.1 He not only taught the subject - although he probably did not teach Copernicus - he trained the other teachers of astronomy in Copernicus 's day, and supplied the text used in the second and more advanced part of the astronomy course. This was his Little commentary on George Peurbach 's 'Theoricae novae planetarum ', completed in 1482, and printed in Milan in 1495.2 It is now generally accepted that Copernicus would have been familiar with Brudzewo 's little commentaryby the time he left Cracow, and that the book contains many items relevant to his later campaign to reform Ptolemaic astronomy.3 On the vexed question of the reality of the celestial orbs, modern commentators usually depict Brudzewo as a fictionalist, that is as denying the physical reality of the orbs introduced by Peurbach in the Theoricae novae. One important case is the late Edward Rosen who classifies Brudzewo as a fictionalist in the last of a series of responses objecting to Noel Swerdlow's work on Copernicus 's first statement of heliocentrism, the Commentariolus, and especially Swerdlow's account of Copernicus 's route to heliocentrism.4 Rosen rejects classifying Brudzewo as a realist on the basis of two frequently quoted passages from the little commentary, which will be discussed in detail below.5 More recently, in an important contribution to Copernicus studies that is especially valuable as a guide to the milieu at Cracow during Copernicus 's education, Andre Goddu also takes Brudzewo to be a fictionalist.6 Goddu, it must be said, does a better job than Rosen, locating many key passages in Brudzewo, correctly identifying him as an opponent of Averroes, and even feeling obliged to explain why, despite being a fictionalist "Because he sometimes reports Peurbach's view, [Brudzewo] seems to agree with Peurbach's realism about spheres, orbs, eccentrics and epicyles".7 Like Rosen, Goddu rejects Swerdlow's account of Copernicus's route to heliocentrism.8 In this paper I will suggest that the common view of Brudzewo is an error based on selective reading and ignoring the context in which Brudzewo was writing. The latter is especially important, as it is only through understanding the context, including the intellectual background and intended audience, that we can correctly evaluate the contents of the Little commentary. Rosen, I will suggest, commits both these errors. To be fair to Goddu, there is evidence for fictionalism in the little commentary. However, a fuller consideration of the contents, together with an examination of the context in which the book appeared, will, I suggest, show that Brudzewo supported the existence of Peurbach's orbs. Two of the most important issues here are locating Brudzewo in the wider dispute between Ptolemaic astronomers and Averroists on the nature of celestial spheres, and examining the other main text used in the astronomy course at Cracow, the commentary on Sacrobosco 's Sphere written by John of Glogow. Glogow's book contains a very clear statement of the reality of Peurbach's orbs, and some other remarks, for example on the equant, that exactly parallel those in Brudzewo.9 If, following Goddu, we acknowledge Glogow and Brudzewo as the two most influential teachers at Cracow in Copernicus 's day, then these conclusions lead to an interesting outcome. First, the case of Cracow provides additional evidence that a significant number of European astronomers before Copernicus accepted that celestial orbs were real. Throughout the elementary astronomy course, students at Cracow were presented with a consistent and clearly stated position on celestial orbs of the type found in Peurbach's Theoricae novae; both main texts, by Glogow and Brudzewo respectively, endorsed the reality of celestial orbs. Cracow thus deserves to be recognized as a centre of innovation in the new approach to astronomy initiated by Peurbach, which spread rapidly throughout Europe in the decades following Copernicus's education. …