i. I. 5 



because man is an animal with such and such characters, therefore 

 is the process of his development necessarily such as it is ; and 

 therefore is it accomplished in such and such an order, this part 

 being formed first, that next, and so on in succession ; and after 

 a like fashion should we explain the evolution of all other works 

 of nature. 



Now that with which the ancient writers, who first philosophised 

 about Nature, busied themselves, was the material principle and 

 the material cause. They enquired what this is, and what its 

 character ; how the universe is generated out of it, and by what 

 motor influence, whether, for instance, by antagonism or friendship, 

 whether by intelligence or spontaneous action,'*' the substratum of 

 matter being assumed to have certain inseparable properties ; 

 fire, for instance, to have a hot nature, earth a cold one ; the former 

 to be light, the latter heavy. For even the genesis of the universe 

 is thus explained by them. After a like fashion do they deal also 

 with the development of plants and of animals. They say, for 

 instance, that the water contained in the body causes by its 

 currents '^ the formation of the stomach and the other receptacles 

 of food or of excretion ; and that the breath by its passage breaks 

 open the outlets of the nostrils ; air and water being the materials 

 of which bodies are made ; for all represent nature as composed 

 of such or similar substances. 



But if men and animals and their several parts are natural 

 phenomena, then the natural philosopher must take into con- 

 sideration [not merely the ultimate substances of which they are 

 made, but also] flesh, blood, bone, and all the other homogeneous 

 parts ; '^ nor only these, but also the heterogeneous parts, such as 

 face, hand, foot, and the like ; and must examine how each of these 

 comes' to be what it is, and in virtue of what force. For to say 

 what are the ultimate substances out of which an animal is formed, 

 to state, for instance, that it is made of fire and water, is no more 

 sufficient, than would be a similar account in the case of an 

 inanimate object, such as a couch or the like. For we should not 

 be content with saying that the couch was made of bronze or' 

 wood or whatever it might be, but should try to describe its 

 design or mode of composition in preference to the material ; or, 

 if we did deal with the material, it would at any rate be with 

 the concretion of material and form. For a couch is such and 

 such a form of this or that matter, or such and such a matter 

 640 b. 



