576 SPECIAL METHODS OF DISCOVERT. 



CHAPTEK LVII. 



DISCOVERT BT COMPARING AND CLASSIFTING KNOWN 

 TRUTHS. 



EVERT truth of nature contains a vast deal more informa- 

 tion than appears in it at first sight ; and some of the 

 additional truth may be evolved from it not only by vary- 

 ing the senses with which we observe it, but also by means 

 of logical analysis and permutation of ideas. 1 



Every different truth, and class of truths, when 

 compared in a new aspect, yield us new knowledge ; 

 and this may be viewed as the law of scientific discovery 

 by means of the senses and intellect. It not only yields 

 us new knowledge, but, if combined with additional 

 truths, either yields more knowledge, or excites in our 

 minds new hypotheses, 2 which, by further experiment 

 or observation, may also lead to new discoveries. We 

 occasionally, without having recourse to new experiments, 

 acquire new knowledge, either by comparing facts and 

 arranging together all those of a similar kind ; comparing 

 collections of facts, and observing their similarities and 

 differences ; arranging a collection of facts in particular 

 orders, and comparing the orders ; or by classifying a col- 

 lection of similar facts in different ways, &c. &c. Dis- 

 coveries, however, are usually made by mentally operating 

 upon new facts ; and in either case a discovery is rarely 

 made by one of these methods alone, but usually by means 

 of several combined, or employed in succession, because of 

 the very intimate relations and dependence of all our 

 intellectual powers. 



1 See p. 333 et seq. 2 See p. 336. 



