72 THE SCIENCE OF LIFE. 



CHAPTER V. 



TYPES OF CONSTRUCTION. 



. . . Much less, then, have we any idea of the substance of God. We 

 know him only by his most wise and excellent contrivances of things and 

 final causes ; we admire him for his perfections ; but we reverence a ul 

 adore him on account of his dominion : for we adore him as his servants ; 

 and a god without dominion, providence, and final causes, is nothing else 

 but Fate and Nature. Blind metaphysical necessity, which is certainly 

 the same always and every-where, could produce no variety of things. All 

 that diversity of natural things which we find suited to different times and 

 places could arise from nothing but the ideas and will of a Being neces- 

 sarily existing. SIR ISAAC NEWTON'S Principia. 



1. OUR imperfect knowledge of nature must always 

 give a provisional character to our classifications. If 

 they present the knowledge we possess in a useful and 

 compact form, it is all they can be -expected to do. Fur- 

 ther knowledge may confirm or overthrow the most per- 

 fectly symmetrical system. Tennyson has well sung : 



" Our little systems have their day, 



They have their day and cease to be, 

 They are but broken lights of thee, 



And thou, O Lord, art more than they." 

 In Mcmoriam. 



Yet an arrangement may be true although imperfect. 

 We may see plainly the leading outline, while a myriad 

 details may be unknown. 



2. In attempting to arrange organic forms it is impos- 

 sible to place them in a single line, like the steps of a 

 ladder, according to structural rank. There are no such 



