OF KNOWLEDGE. 399 



understood, and it has also somewhat changed through 

 the development of these sciences themselves. 



A few examples of this change and of its causes will 

 suffice to show how the problem of knowledge has 

 assumed a different aspect. Kant's view of nature was 

 to a large extent comprised in that circle of notions 

 which I have in an earlier chapter termed the astronomi- 

 cal view of nature. He worked with the conceptions of 

 attraction and repulsion, of action at a distance. These 

 notions, which are as old as philosophy itself, had re- 

 ceived an exact definition through Newton's principle 

 of gravitation and through the measurement of electric 

 actions, all of which came under the same numerical 

 relation. Accordingly not only Kant, but still more 

 specifically Laplace and his school, made this numerical 

 relation which obtained in all actions at a distance the 

 fundamental principle of their natural philosophy. The 

 warning of Newton that the principle involved could 

 not be considered as ultimate, but itself demanded a 

 further explanation, was forgotten till well on into the 

 nineteenth century. Even Helmholtz, who did so much 

 in the middle of the century to bring about the great 

 change I am speaking of, stated, in his celebrated tract 

 " On the Conservation of Force," that natural phenomena 

 might be supposed to be explained if they were reduced 

 to a combination of central forces acting at a distance. 

 Neither can it be denied that, to the popular mind, 

 action at a distance, attraction and repulsion, are of such 

 common occurrence, and are met with in so many 

 different forms, that they have, through habit, become 

 elevated to the position of ultimate not further analys- 



