122 Darwinism and Other Essays. 



hypothesis, handed down to us from barbarous 

 times, which has been uniformly discredited wher- 

 ever there has been an opportunity for testing it. 

 Even to describe such a " force " as " psychic " is 

 to beg the whole question ; for until we have sub- 

 jected it to a long course of experimentation, like 

 that which has built up our scientific knowledge 

 of heat and light, we can have no means of know- 

 ing whether it is " psychic " or not. 



It is, however, very un philosophical at the out- 

 set to appeal to any new or unknown force until 

 we have thoroughly exhausted all means of ex- 

 planation furnishable by forces that have already 

 been defined ; and by the advocates of spiritualism 

 no such preliminary inquiry has ever been made 

 or even attempted. When, therefore, Mr. Crookes 

 finds himself unable to explain the way in which 

 Mr. Home causes the index of a spring-balance to 

 descend without exerting any apparent pressure 

 on the lever, it is a very violent stretch of in- 

 ference to call in an imaginary " psychic force " 

 by way of simplifying the matter. This is ap- 

 pealing from the known to the unknown, and it 

 is in no such way that discoveries are made in 

 those physical sciences which Mr. Crookes has so 

 carefully studied. Dr. Hammond may well say 

 that " there are so many ways in wbietTknown 



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