Abstract

The idea of reconciling Ptolemaic planetary theory with Aristotelian natural philosophy by imagining epicycles and eccentric deferents as three-dimensional orbs or orb-segments within larger spheres is frequently associated with Georg Peurbach and his widely read astronomy textbook, the Theoricae novae planetarum (1454). This article cautions against existing tendencies to overstate the originality or revolutionary force of this work by taking a closer look at the early history of the same Ptolemaic-Aristotelian compromise in a Latin European context. Using previously unpublished or unused source material from the twelfth to early fourteenth centuries, it documents the gradual spread and acceptance of an orbicular interpretation of Ptolemy’s planetary models among astronomers and university teachers.