CELESTIAL MOVERS IN MEDIEVAL PHYSICS IGl 



to say that if there wefe no metaphysics, arithmetic would be 

 the supreme universal science. This contrast, however, with 

 the view of St. Albert and St. Thomas is not perfectly symetri- 

 cal, since Kilwardby did not consider metaphysics to rest on 

 the real existence of " substance other than those which are 

 formed by nature." Nevertheless a clear contrast can be seen 

 between the Platonic orientation upward from nature to mathe- 

 matics and the Aristotelian orientation subordinating mathe- 

 matics to natural philosophy. St. Albert and St. Thomas both 

 defended the autonomy of natural science within the limits of 

 its own piincipia propria illuininantia, distinct from meta- 

 physics and superior to mathematics.^^ 



The third peculiar characteristic of astronomy recognized in 

 the Middle Ages was the special role it had in the discovery of 

 God's existence. This characteristic was not entirely new. In 

 pagan mythology the celestial bodies were themselves con- 

 sidered gods or at least the inhabitation of the gods. Pagan 

 philosophers such as Plato and Aristotle did not hesitate to call 

 celestial bodies divine. Ptolemy himself saw in astronomy the 

 only secure path to theology: 



For that special mathematical theory would most readily prepare 

 the way to the theological, since it alone could take good aim at 

 that unchangeable and separate act [God], so close to that act are 

 the properties having to do with translations and arrangements of 

 movements, belonging to those heavenly beings which are sensible 

 and both moving and moved, but eternal and impassible.^ 



34 



Al-Bitruji, St. Albert frequently points out, had this advantage 

 over the complicated system of Ptolemy that he considered 

 all celestial motions to be derived from a single first mover, who 

 is God.^^ For Kilwardby the path to God rose more tortuously 



''^Cf. J. A. Weisheipl, " Albertus Magnus and the Oxford Platonists," ed. cit., 

 pp. 136-139. 



^* Ptolemy, Almagest, Bk. I, chap. 1, trans, by R. C. Tahaferro (Great Books of 

 the Western World, 16; Chicago, 1952), p. 6. 



^^ Al-Bitruji, De motibus celorum, III, 10-14, trans, by Michael Scot, ed. Francis 

 J. Carmody (Berkeley: Univ. of California, 1952), pp. 79-80; St. Albert, Prob- 

 Jeviata Determinata, q. 1, ed. cit., p. 321; Liber de causis, I, tr. IV, c. 7, ed. 

 Borgnet X, 426b-427b; lib. II, tr. II, c. 1, ed. Borgnet X, 479b-480a et alibi. 



