CELESTIAL MOVERS IN MEDIEVAL PHYSICS 159 



of the universe, the moving causes of celestial motion, their 

 number and order, are obvious. Consequently this part of 

 natural philosophy abounds with tentative views and argu- 

 ments, having need of mathematical astronomy to suggest 

 possibilities. Discussing the number of celestial movements, 

 Aristotle himself realized the need of " that one of the mathe- 

 matical sciences which is most akin to philosophy, namely of 

 astronomy." ^" He was unable to determine the exact number 

 of distinct celestial motions, but he tentatively adopted the 

 astronomical hypotheses of Callippus minus eight uncertain 

 motions, taking the number of spheres to be forty-seven. From 

 this he argued that " the unmovable substances and principles 

 also may probably be taken as just so many; the assertion of 

 necessity must be left to more powerful thinkers." "^ That there 

 must be many movements and movers was accepted by St. 

 Albert and St. Thomas as certain, but their exact number was 

 hypothetical and not essential to the argument pursued.^* 



In other words, for St. Albert and St. Thomas mathematical 

 astronomy and the other physical parts of mathematics are 

 considered as ordained to the discovery of physical causes in 

 natural philosophy. The mathematical sciences are, as it were, 

 the dialectical preparation for the real demonstrations in na- 

 tural philosophy. Since all mathematics, even the more physi- 

 cal parts of mathematics, prescind from motion and sensible 

 matter,-^ they are that much removed from reality and need 

 to be evaluated by that science which studies nature as it really 

 exists, in Tuotu et inabstracta. That is to say, the mathe- 

 matical sciences are subordinated to and ordained to the phi- 

 losophy of nature. Consequently, " if there were no substance 

 other than those which are formed by nature, natural science 

 would be the first science." ^^ 



" Metaph., XII, c. 8, 1073b4-5. 

 "/fete?., 1074al5-17. 



" St. Albert, Lib. XI Metaph., tr. II, c. 17 & c. 27; St. Thomas, In XII Metaph., 

 lect. 9, n. 2565; lect. 10, n. 2586. 

 "Boethius, De Trinitate, c. 2. 

 ''"Metaph., VI, c. 1, 1026a28-29, and XI, c. 7, 1064b9-10. 



