ON CONCEPTION. 583 



convertible into the cluck, and is in fact the chicken in posse. 

 Let B be that which fecundates the egg, and thus distinguishes 

 it from an unfruitful egg, i. e. the " efficient cause" of the 

 chick, or that which puts the egg in motion, and converts it 

 into a chick. And let C be the chick, or " final cause," for 

 the sake of which both the egg and that which fecundates the 

 egg exist, the actual chick, namely, or "reason" why the 

 chick is. 



Now we take for granted, as demonstrated by Aristotle, 1 

 that every prime mover is " combined with" that which is 

 moved by it. And these things are more particularly said 

 by him to be " together" which are generated or produced at 

 the same moment of time : thus that which moves and that 

 which is moved are actually together, and where one is there 

 the other is also ; for it is evident that when the effect is present 

 the cause must be so too. 



Whenever, then, A (i. e. the fecundated egg) is actually in 

 being, B (i. e. the internal moving and "efficient" or fecundating 

 cause) is also actually in being. But when B is actually in 

 being, C also (i. e. the immaterial " form" of the chick) must, 

 at least in some sort, be existing too. For B is the internal 

 efficient cause of the chick, that, namely, which alters A (the 

 egg) into C (the "reason" why the chick is). Since, then, 

 everything which moves coexists with that which is moved by 

 it, and every cause with its effect, it follows that C coexists 

 with B ; for the " final cause," both in nature and art, is pri- 

 mary to all other causes, since it moves, and is not itself moved; 

 but the " efficient" moves, because it is impelled by the " final 

 cause." There inheres, in some way or other, in every "effi- 

 cient cause" a ratio finis (a final cause), and by this the efficient, 

 co-operating with Providence, is moved. 



The authority of Aristotle is clearly on my side : " That," 

 he says,2 " appears to hold the chief place among natural causes 

 which we signify under this expression, ' cujus gratia/ for 

 whose sake. For this is the 'reason/ but the 'reason' is the 

 chief thing, as well in artificial as in natural subjects. For 

 when a physician explains what health is, either by definition 

 or description, or a workman a house, he is accustomed to give 



1 Plusiologia, lib. vii, cap. 3. 3 De Part. Anirn. lib. i, cap. 1. 



