PARTS OF ANIMALS, II. i. 



substances. (3) The third and last is the composition 

 of the " non-uniform " parts of the body, such as 

 face, hand, and the Hke. 



Now the order of things in the process of formation 

 is the reverse of their real and essential order ; I 

 mean that the later a thing comes in the formative 

 process the earlier it comes in the order of Nature, 

 and that which comes at the end of the process is at 

 the beginning in the order of Nature. Just so bricks 

 and stone come chronologically before the house, 

 although the house is the purpose which they sub- 

 serve, and not vice versa. And the same applies to 

 materials of every kind. Thus the truth of my state- 

 ment can be showTi by induction ; but it can also 

 be demonstrated logically, as follows. Everything 

 which is in process of formation is in passage from 

 one thing towards another thing, i.e. from one Cause 

 towards another Cause ; in other words, it proceeds 

 from a primary motive °' Cause which to begin with 

 possesses a definite nature, towards a Form or an- 

 other such End. For example, a man begets a man 

 and a plant begets a plant. These new indi- 

 viduals are made out of the substrate matter appro- 

 priate in each case. Thus, matter and the process 

 of formation must come first in time, but logically^ 

 the real essence and the Form of the thing comes 

 first. This is clear if we state the logos ^ of such a 

 process. For example, the logos of the process of 

 building includes the logos of a house, but that of a 

 house does not include that of the process of building. 

 And this holds good in all such cases. Hence we 

 see that the matter, viz. the Elements, must exist 

 for the sake of the uniform substances, because 

 these come later in the process of formation than 



109 



