SKEPTICISM AND IDOLATRY 199 



see later that Poincare absolutely reverses this opinion, 

 rejects matter and clings to the ether; meanwhile, both 

 of his opinions are unsupported by experimental evi- 

 dence, which he has declared to be the touchstone of 

 truth and usefulness for hypotheses. Not only does 

 Poincare drift in this hopeless fashion between matter 

 and ether, but the founders of the New Mechanics are 

 at sea as regards the existence of the ether. One 

 school of thought claims that all substance is but a 

 differentiation of the ether, which thus becomes uni- 

 versal substance; the other school is just as positive in 

 its belief that the ether is a wornout fiction. In spite 

 of this trifling difference in their points of view, both 

 schools arrive at much the same conclusions. At 

 least they give us a good illustration of the power of 

 mind to modify matter. During the recent conference 

 at Brussels for the purpose of discussing the new con- 

 cepts of matter and mechanics, Poincare suggested 

 that it was unfortunate that physicists were using the 

 ether when they needed it, and were discarding it when 

 it proved troublesome. Curiously, no one in the con- 

 ference seemed to find the situation of the New Me- 

 chanics in the least embarrassing or humorous; the fact 

 is, the consequences announced at the conference were 

 so unintelligible that a sense of humor would have 

 been out of place. 



Although Poincare says that we must generalize, 

 and that every generalization is an hypothesis, still 



