254 SHEiLAH o'flynn brennan 



passive principle, while principium activum et formate would 

 be reserved for the principle by which a thing moves itself by 

 itself. But this answer creates difficulties as soon as we observe 

 that in other places the principle of falling in heavy bodies is 

 explicitly given not as a passive but as an active principle/^ 



The solution to this apparent contradiction lies in an ex- 

 planation of what is meant by active principle. The formal 

 principle is not necessarily active as in an agent, or in a living 

 being in which one part moves another. In the passage in 

 which the fonii of a heavy body is said to be an active principle, 

 what is meant apparently is not that the form moves the body 

 as an agent cause or even that it is a principle by which the 

 body moves itself, but that it is the ever-present source of the 

 motion — of the activity. In this way, it is distinguished from 

 a passive, i. e. receptive, principle which requires for the tran- 

 sition into act the presence of an agent, as when water is 

 being heated. Even in non-living things, consequently, nature 

 may be regarded as an active principle, though in living beings 

 it is active in a special way. 



When St. Thomas states, then, that the form of the heavy 

 body is a passive principle and explains further that the body 

 is moved rather than moves, his intention in these passages, 

 evidently, is to distinguish the heavy body from the living 

 being.^* For though the falling body moves, and moves indeed 

 without the actual influence of an agent cause, it, nevertheless, 

 does not move itself in the sense that it is an agent (a mover) 

 with respect to itself, as is the living being. The mover in the 

 case of the falling body would be the original maker that pro- 

 duced the form it has, making it the type of thing it is, with all 

 its concomitant characteristics, including its tendency to fall 

 when raised from the ground. ^^ 



The passive material principle, on the other hand, is a re- 

 ceptive principle. It is especially prime matter with its appetite 



" Cf ., e. g., Contra Gentiles, IV, 97. 



" Cf. Arist., Physics, VIII, ch. 4; St. Thomas, In VIII Phys., lect. 8, n. 7, where 

 jmncipium fossivum is distinguished from the principium motivum aut activum. 

 ^^ Cf . St. Thomas, In II Phys., lect. 1, n. 4. 



