It has always been a problem to me how this could 

 have happened. It can, indeed, be explained only on the 

 supposition that naturalists were adverse to the introduc- 

 tion of anything into nature, that appeared to them mystic- 

 al and mysterious. Nor is such a procedure at all neces- 

 sary: vital force is by no means a mysterious, ghostly 

 power that soars above nature, but a force of na- 

 ture like its other forces, as mysterious and as 

 definite as they are, only that it dominates a speci- 

 fied group of beings, namely, living organisms. It 

 may readily be compared with any other natural 

 phenomenon. For instance, the phenomenon of crystaliza- 

 tion has its well determined sphere of activity, viz., the 

 mineral world. It employs definite mathematico-physical 

 laws to obtain a specified result, and even acts diflferently 

 in different mineral substances in so far as it produces in 

 the one case this, in the other case that form; but still it 

 should be a similarly directed force which has the effect 

 of producing these peculiar forms. Precisely similar is it 

 with vital force. It has its determined sphere of activity, 

 the kingdom of living organisms; it acts according to defi- 

 nite physico-chemical laws in producing a specified result; 

 it acts differently in different living organisms; it is there- 

 fore a force of nature as clear yet as mysterious as the 

 force of crystallization or as any other force of nature. 

 Hence one has no cause to complain of its mysteriousness, 

 for all other forces of nature are just as much, or if you 

 will, just as Uttle mysterious as vital force. The only thing 

 to be maintained is this, that living organisms are domi- 



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