INTRODUCTION. 13 



the internal connexion not only of forces, but also of organic 

 forms. In his book on the parts (organs) of animals, he clearly 

 intimates his belief that throughout all animate beings there 

 is a sqale of gradation, in which they ascend from lower 

 to higher forms. Nature advances in an uninterrupted pro- 

 gressive course of development, from the inanimate or " ele- 

 mentary" to plants and animals; and "lastly, to that which, 

 though not actually an animal, is yet so nearly allied to one, 

 that on the whole there is little difference between them." 19 

 In the transition of formations, "the gradations are almost 

 imperceptible." 20 The unity of nature was to the Stagirite 

 the great problem of the Cosmos. " In this unity," he 

 observes, with singular animation of expression, " there is 

 nothing unconnected or out of place, as in a bad tragedy."' 21 

 The endeavour to reduce all the phenomena of the universe 

 to one principle of explanation, is manifest throughout the 

 physical works of this profound philosopher and accurate ob- 

 server of nature ; but the imperfect condition of science, and 

 ignorance of the mode of conducting experiments, i.e., of calling 

 forth phenomena under definite conditions, prevented the com- 

 prehension of the causal connection of even small groups of phy- 

 sical processes. All things were reduced to the ever-recurring 



19 Aristot. de partibus Anim., lib. iv. cap. 5, pag. 681, 

 lin. 12. Bekker. 



20 Aristot. Hist. Anim., lib. ix., cap. 1, pag. 588, lin. 10-24. 

 Bekker. When any of the representatives of the four ele- 

 ments in the animal kingdom on our globe fail, as for instance 

 those which represent the element of the purest fire, the 

 intermediate stages may perhaps be found to occur in the 

 moon (Biese, Die Phil, des Aristoteles, bd. ii. s. 186). It is 

 singular enough, that the Stagirite should seek in another 

 planet those intermediate links of the chain of organised 

 beings which we find in the extinct animal and vegetable 

 forms of an earlier world. 



21 Aristot. Metaph. lib. xiii. cap. 3, pag. 1090, lin. 20, 

 Bekker. 



