XIII. 



ERRONEOUS DEDUCTION. 



CONSIDERED simply as a logical process, 

 ^-^ deduction is no more interesting in the 

 hands of the modern investigator than it was 

 in the hands of the mediaeval schoolman. The 

 scientist uses it, apart from its importance in 

 proof, or effort to convince others, merely as an 

 instrument with which to test what is known, 

 and to develop its unknown consequences. The 

 infallibility of the process is altogether hypo- 

 thetical. The conclusion is true only if "the 

 premises are true; and since the truth of the 

 premises is oftener the matter in question than 

 even the investigator dreams, the effort to get 

 at new truth by anticipating the consequences 

 of theory often results in false conclusions. 

 This must especially be the case when there is 

 no apparent reason to question the truth of the 

 premises ; when they would seem to have been 

 permanently established by repeated crucial 

 tests. In a number of instances Darwin went 



