SUBJECTIVE AND OBJECTIVE METHODS 



some crucial experiment ; there is nothing ano- 

 malous in the fact of two such thoroughly sci- 

 entific evolutionists as Professor Huxley and 

 Dr. Bastian holding opposite opinions as to its 

 merits.^ But it would not be in keeping for two 

 scientific philosophers to wrangle over Leibnitz's 

 doctrine of Pre-established Harmony, because 

 that is a hypothesis which can never be proved 

 or disproved. The data necessary for its verifi- 

 cation do not exist, and therefore no system of 

 philosophy, which would keep clear of meta- 

 physics, can recognize it as a legitimate sub- 

 ject for investigation. Again, in the eighteenth 

 century there were two rival theories of light. 

 According to the theory of Newton, a ray of 

 light is a linear series of material corpuscles, 

 darted from the luminous object. According to 

 the theory of Huyghens, a ray of light is a sys- 

 tem of molecular undulations which move out- 

 ward in ever-increasing concentric shells whose 

 normals are radial, and which are set in motion 

 by undulations among the molecules of the 

 luminous object. At the beginning of the pre- 

 sent century the corpuscular theory was sub- 

 mitted to a set of crucial investigations which 

 overthrew it; and more recently the undulatory 

 theory has been submitted to a course of crucial 



^ [As is well known, this controversy has now long since 

 been settled, against the hypothesis of ** spontaneous genera- 

 tion " as held by Dr. Bastian at the time here in question.] 

 191 



