352 SCIENTIFIC THOUGHT. 



genetic view of nature, drawing likewise into this circle 

 of ideas the great departments of anthropology and 

 geography ; in fact, it amounts to rewriting the ' Kosmos ' 

 of Humboldt on genetic instead of on purely descriptive 

 lines. But in perusing these and similar writings of 

 modern times, we feel on the one side that we are 

 gradually getting out of the depths of science, not only 

 into the domain of conjecture, without which a know- 

 ledge of the past cannot be gained, but also into the 



46. regions of philosophical thought, which proceeds on 

 ieaiprob- other lines than those prescribed to science, and which 



lems. 



will claim our attention in a special portion of this 

 work. On the other side, in using so confidently the 

 ideas of descent and adaptation, we feel that we are 

 appealing to two great empirical facts, the facts of 

 heredity and of variation of living things, on which the 

 genetic view of nature, when applied to the living 

 portion of creation, rests, but which are scarcely even 

 defined in clear terms, much less explained. In fact, 

 we are face to face with the problem and definition of 

 life itself. Neither the morphological nor the genetic 

 view of nature is limited to the living world, although 

 both views originated there, and were from thence ex- 

 tended to the larger domain of inorganic and cosmical 

 phenomena. Into these larger views which try to 

 grasp the forms of nature in their apparent rest or in 

 their endless change and history, the phenomena of 

 life have been fitted by the help of three definite con- 



47. ceptions the conception of the cell as the morpho- 



Problem of 



life. logical basis or unit of all life, and the two concep- 



tions of inheritance and variation, by which living 



