C>'2 THK PROGRESS <>F S< Ii:\ n 



progress has been the invention of verifiable 

 hypotheses. It is a favourite popular delusion 

 that the scientific inquirer is under a sort of moral 

 obligation to abstain from going beyond that 

 generalisation of observed facts which is absurdly 

 called " Baconian " induction. But any one wl i 

 practically acquainted with scientific work is 

 aware that those who refuse to go beyond fact, 

 rarely get as far as fact ; and any one who 

 has studied the history of science knows that 

 almost every great step therein has been made by 

 the " anticipation of Nature," that is, by the 

 invention of hypotheses, which, though verifiable, 

 often had very little foundation to start with ; 

 and, not unfrequently, in spite of a long career of 

 usefulness, turned out to be wholly erroneous in 

 the long run. 



The geocentric system of astronomy, with its 

 eccentrics and its epicycles, was an hypothesis 

 utterly at variance with fact, which nevertheless 

 did great things for the advancement of astrono- 

 mical knowledge. Kepler was the wildest of 

 guessers. Newton's corpuscular theory of liir 

 was of much temporary use in optics, though 

 nobody now believes in it; and the undulatm-y 

 theory, which has superseded the corpuscular 

 theory and has proved one of the most fertile 

 of instruments of research, is based on the 

 hypothesis of the existence of an "ether," the 

 properties of which are defined in propositions, 



