CELESTIAL MOVERS IN MEDIEVAL PHYSICS 165 



value to the modern Thomist, however much the modern 

 Thomist may wish to adapt the traditional arguments. 



To understand the problem of celestial movers in medieval 

 physics, it is necessary to present the views of Albertus Magnus 

 and then those of Robert Kilwardby before examining the cru- 

 cial problem in the doctrine of St. Thomas. 



St. Albert the Great 



For St. Albert both physics and metaphysics attain the 

 existence of God, but under different formalities and in different 

 ways. Physics, although it demonstrates through all the real 

 causes in nature, is primarily concerned with the efficient and 

 material cause: " if we have said anything about the form or 

 about the end [in physics], this was only of form insofar as it is 

 mobile and of end only insofar as it is the termination of the 

 motion of a mover." " But metaphysics deals with substantial 

 being and its causes; therefore in metaphysics " we directly 

 show that the first efficient cause is the universal end, that 

 from him flow all mobile substances, and that he is like a leader 

 of an army with respect to the universe." ** This task is proper 

 to metaphysics, and in this respect nothing is borrowed from 

 natural science. It is true that natural science proved by way 

 of motion the absolute immobility of the first mover, but it did 

 not reveal him prout ipsum est causa universi esse et forma et 

 finis. This is proper to metaphysics. Hence, Albert concludes, 

 it is evident that metaphysics is a loftier contemplation by far 

 than physics. 



The task of physics is to explain all changes in nature, both 

 terrestrial and celestial. Terrestrial movements, alteration, 

 generation and corruption can be explained in large measure 

 by the celestial bodies, but since these celestial bodies them- 

 selves are moved, the ultimate source of this movement must 

 itself be immovable. This ultimate unmoved mover, proved 

 in the Physics, is considered by St. Albert to be God, the 



" St. Albert, Lib. XI Metaph., tr. I, c. 3, ed. cit., VI, 584b. 

 " Ibid. 



