CELESTIAL MOVERS IN MEDIEVAL PHYSICS 169 



since celestial motions do not attain any end, these motions 

 cannot arise spontaneously from the nature of celestial bodies. 

 For St. Albert, as for Plato and Aristotle before him, celestial 

 motions must be derived immediately from some kind of soul, 

 or self-mover. 



Comparing the views of Plato and Aristotle,^® Albert notes 

 that both agree on three points: (i) that all natural motions 

 must be reduced to some self-movent; (ii) that a celestial body 

 cannot move itself, but must be moved by a spiritual substance 

 which is either a soul or an intellect; (iii) that the spiritual 

 mover of the body must itself be indivisible, without magni- 

 tude, possessing adequate power to move the celestial body. 

 However, Albert notes, Plato and Aristotle differ on two essen- 

 tial points: (i) Plato considered the conjoined mover to be the 

 ultimate mover, while Aristotle considered this soul to be the 

 instrument of a higher intellect entirely separated from all mat- 

 ter; (ii) Plato considered the celestial soul to be perpetual and 

 descendent from the stars, while Aristotle conceived the con- 

 joined mover to be produced by the separated intellect and 

 moved by it. In other words, Aristotle, according to St. Albert's 

 understanding, admitted a conjoined mover for each celestial 

 motion, a mover which was somewhat similar to a spiritual, 

 intellectual soul, but without sense faculties. This conjoined 

 mover explained how a celestial body like the primum caelum 

 could be moved perpetually without attaining any end or 

 finality intrinsic to itself. However, the conjoined mover itself 

 was moved by reason of the celestial body; that is, the anima 

 caeli moved concomitantly {per accidens) with the celestial 

 body, much as the human soul is moved by the movement of 

 the body. Therefore, the anima caeli is a moved mover, needing 

 to be moved by another, a substance entirely separated from 

 matter not only in definition, but also in existence. The spirit- 

 ual anima caeli can be moved only by intellection and desire. 

 The initial intellectual light emanating from the subsisting act- 



^» St. Albert, Lib. VIII Phys., tr. U, c. 8. 



