CHAPTER NINE COPERNICUS AS NATURAL PHILOSOPHER 1. Introduction When two of the leading experts on Copernicus characterized him as an Aristotelian, they were without doubt referring to his retention of celestial spheres as the movers of the planets and to his views in natu- ral philosophy.1 Although other experts have pointed to non-Aristote- lian sources of Copernicus’s account of motion and natural elemental motion, I have concluded that Copernicus also drew on schools and communities of the Aristotelian tradition. He combined them into an uneasy synthesis with all of the ambiguities and inconsistencies that one would expect. Teachers and students within the Aristotelian tradi- tion modifi ed Aristotelian doctrine, oft en interpreting it in ways that combined the fundamental principles of other authors and Judaic- Christian doctrines, and thereby created a synthesis that is diffi cult to 1 Rosen, Introduction to Letter, Complete Works, 3: 134, comments: “[F]amiliarity with Aristotle’s treatises does not of course make Copernicus an Aristotelian in the sense that he regarded the Stagirite as infallible. On the contrary, where he detected a fl aw in Aristotle, as in the Stagirite’s division of simple motion into three mutually exclusive types, he did not hesitate to correct it. But he did not undertake to over- throw Aristotelianism, as he did the Ptolemaic astronomy. On the other hand, what he believed was sound in both systems, he retained with gratitude and aff ection, an attitude which some of our contemporaries would do well to consider.” Compare with the assertion of Swerdlow, “Copernicus,” 162–168, esp. 164–165: “For these physical problems raised by the motions of the earth, which should also aff ect the motion of birds, clouds, and projectiles, Copernicus made what he considered to be a minimal alteration of Aristotelian natural motion of the elements, such that the natural motion of a spherical body, whatever its substance, is to rotate in place by virtue of its form alone. Th e daily rotation of the spherical earth together with the surrounding water and air is, therefore, entirely natural; projectiles, birds, and clouds are simply carried along with the rotating earth; and heaviness (gravitas), the descent of heavy bodies to their natural place, the surface of the earth, in straight lines, is due to a ‘natural inclination placed in the parts’ to come together to form a globe. In proposing this explanation, Copernicus did not intend to overthrow or displace Aristotelian physics but to adapt it to the motion of the earth, unlike Galileo Galilei (1564–1642), who later used much the same principles as Copernicus for a devastating attack on Aristotle. In fact, the objections to the motion of the earth were not completely answered until Isaac Newton (1642–1727).” 326 chapter nine reconcile with genuine Aristotelianism. Be that as it may, this was the Aristotelianism that Copernicus encountered, and it is far from clear how much he realized or, for that matter, even cared about the authen- ticity of classical authors’ views. Or, to put it diff erently, his concern, shared by the authors of the Aristotelian tradition, was to arrive at the truth, and to adopt Aristotelian views where they agreed and adapt his views where they did not.2 2. Copernicus’s Critique of Geocentrism In chapter four, I summarized the principal Aristotelian cosmologi- cal assumptions and conclusions relevant to Copernicus’s arguments. From the point of view of natural philosophy and physics in particu- lar, we have been conditioned to view Copernicus as having antici- pated the successful mechanical principles enunciated defi nitively by Newton some one hundred and forty-four years aft er the appear- ance of De revolutionibus. Despite the successful historical revision of Copernicus’s astronomical achievements as a conservative continu- ation and even fulfi llment of the goals of Ptolemaic astronomy, the topos of anticipation still dominates the standard representations of his vision of cosmology, natural philosophy, and physics.3 Even when some readers acknowledge the survival of Platonic and Aristotelian principles in Copernicus’s understanding of cosmology, they have still left the impression that he anticipated essentially anti- Aristotelian solutions to several problems and questions. Because of the success of the Newtonian program, such readings of Copernicus seem plausible.4 2 See chapter four on the Aristotelian tradition and on Aristotelian schools and sects. 3 An excellent example is Pedersen and Pihl, Early Physics, 317. Th is text provides one of the best accounts of ancient and early modern astronomy but reads Copernicus’s intentions about natural philosophy from the viewpoint of contemporaneous negative reactions by Aristotelians and from the viewpoint of later physical astronomy. In his text, Birth, chs. 1–3, Cohen adopts for pedagogical purposes a portrayal of Aristotelian dynamics that was so incompatible with the Copernican theory that a new theory had to be developed. My own earlier essays, for example, Goddu, “Dialectic,” 95–131, at 125–131, also portray Copernicus as having left the physical questions for a later day, thus suggesting that Copernicus anticipated a non-Aristotelian solution. 4 Exceptions are Moraux, “Copernic et Aristote,” 225–238, and Swerdlow, “Coper- nicus,” 163..