136 THE PRINCIPLES OF SCIENCE. 



adopted hypothetical reasoning to the exclusion of ex- 

 perimental verification. Throughout the eighteenth cen- 

 tury science was supposed to be advancing by the pur- 

 suance of the Baconian method, but in reality hypothetical 

 investigation was the main instrument of progress. It is 

 only in the present century that physicists began to recog- 

 nise this truth. So much opprobrium had been attached 

 by Bacon to the use of hypotheses, that we find Young 

 speaking of them in an apologetic tone. ' The practice of 

 advancing general principles and applying them to par- 

 ticular instances is so far from being fatal to truth in all 

 sciences, that when those principles are advanced on suf- 

 ficient grounds, it constitutes the essence of true phi- 

 losophy 01 '; and he quotes cases in which Sir Humphry 

 Davy trusted to his theories rather than his experiments. 

 The late Sir John Herschel, who was both a practical 

 physicist and an abstract logician, always entertained the 

 deepest respect for Bacon, and made the 'Novum Organum ' 

 as far as possible the basis of his admirable ' Discourse on 

 the Study of Natural Philosophy/ Yet we find him in 

 Chapter VII fully recognising the part which the forma- 

 tion and verification of theories forms in the higher and 

 more general investigations of physical science. The late 

 Mr. J. S. Mill carried on the reaction by recognising as a 

 distinct method the Deductive Method in which Ratio- 

 cination, that is, deductive reasoning, is employed for the 

 discovery of new opportunities of testing and verifying 

 a hypothesis. His main error consisted in the fact that 

 throughout the other parts of his system he inveighed 

 against the value of the deductive process, and even 

 asserted from time to time that every process of reasoning 

 is inductive. In fact Mill fell into much confusion in the 

 use of the words induction and deduction, because he 



d Young's Works, vol. i. p. 593. 



