RATING A THEORY 25 



fact is sufficient to disprove the soundness of any 

 hypothesis. Thus, "it is the modern custom now," 

 as observed some years ago by Shaler, "to term 

 the supposition of an explanation a working hy- 

 pothesis, and only to give it the name of theory 

 after a very careful search has shown that all the 

 facts which can be gathered are in accordance with 

 the view." "In its most proper acceptation," ac- 

 cording to J. S. Mill, "theory means the completed 

 result of philosophical induction from experience." 



A theory that does not account for all the 

 facts which are involved is an inadequate solution. 

 In order to be entirely acceptable, a theory must 

 be both sufficient and necessary. This means that 

 the theory must fully account for the phenomena 

 under consideration, and that they cannot be thus 

 accounted for on any other hypothesis. 



When thus fully accounted for, the phenomena are 

 (in popular language) said to be "explained." "To 

 'explain' means," as Hans Driesch defines, "to sub- 

 sume under known concepts, or rules, or laws, or prin- 

 ciples, whether the laws or concepts themselves be 

 'explained' or not. Explaining, therefore, is always 

 relative: what is elemental, of course, is only to be 

 described, or rather to be stated."^ 



"A scientific explanation," John Fiske points out, 



^ The Science and Philosophy of the Organism, 51. 



