In the early 1540ies G.J. Rheticus wrote an anonymous treatise entitled both Epistola deTerrae Motu and Dissertatio de Hypoth[esibus] Astron[omiae] Copernicanae. In thisletter he discusses why proclaiming the motion of the earth does not need to beconsidered as an impious act incompatible with the words of Holy Scripture. Based onan analysis of authorities mentioned by the author in this letter, I conclude thatRheticus’ strategy on the one hand consists in playing down the importance of thetraditional Aristotelian-Ptolemaic notions on the universe in the field of astronomy andby emphasizing the indirect character of Biblical authority in these matters. On the otherhand, he claims the absolute, immediate authority of mathematics in astronomy bywhich he consequently challenges the traditional medieval hierarchy of sciences.Rheticus considers the achievements of Copernicus to be part of divine providence.
