30 THE HISTOEY OF CREATION. 



properties have not as yet been observed by the experience 

 of the senses. But Da^^win's theory does not assume such 

 unknown conditions ; it is based upon general properties 

 of organisms that have long been recognized, and — as has 

 been remarked — it is the exceedingly ingenious and com- 

 prehensive combination of a number of phenomena which 

 had hitherto stood isolated, which gives the theory its 

 extraordinarily great and intrinsic value. By it we are 

 for the first time in a position to demonstrate an active 

 cause for all the known morphological phenomena in the 

 animal and vegetable kingdoms; and, in fact, this cause is 

 always one and the same, viz. the alternate action of Adap- 

 tation and Inheritance, therefore a physiological, that is, a 

 physico-chemical or mechanical, relationship. For these 

 reasons the acceptance of the Doctrine of Filiation, as 

 mechanically established by Darwin, is a binding and un- 

 avoidable necessity for the whole domain of zoology and 

 botany. 



As, therefore, in my opinion the immense importance of 

 Darwin's theory lies in the fact that it has mechanically 

 explained those organic phenomena of for'.ns which had 

 hitherto been unexplained, it is perhaps necessary that I 

 should here say a few words about the different ideas con- 

 nected with the word " explanation." It is very frequently 

 said, in opposition to Darwin's theory, that it does indeed 

 explain those phenomena by Inheritance and Adaptation, 

 but that it does not at the same time explain those pro- 

 perties of organic matter, and that therefore we do not 

 arrive at first causes. This objection is quite correct, but it 

 applies equally to all explanations of phenomena. We no- 

 where arrive at a knowledge of fii'st causes. The origin of 



