CHAPTER I. 



INTRODUCTORY REMARKS. 



1. PRINCIPLES of Evidence and Theories of Method are 

 not to be constructed a priori. The laws of our rational 

 faculty, like those of every other natural agency, are only learnt 

 by seeing the agent at work. The earlier achievements of 

 science were made without the conscious observance of any 

 Scientific Method ; and we should never have known by what 

 process truth is to be ascertained, if we had not previously 

 ascertained many truths. But it was only the easier problems 

 which could be thus resolved : natural sagacity, when it tried 

 its strength against the more difficult ones, either failed alto- 

 gether, or if it succeeded here and there in obtaining a solu- 

 tion, had no sure means of convincing others that its solution 

 was correct. In scientific investigation, as in all other works 

 of human skill, the way of obtaining the end is seen as 

 it were instinctively by superior minds in some compara- 

 tively simple case, and is then, by judicious generalization, 

 adapted to the variety of complex cases. We learn to do 

 a thing in difficult circumstances, by attending to the manner 

 in which we have spontaneously done the same thing in easier 

 ones. 



This truth is exemplified by the history of the various 

 branches of knowledge which have successively, in the ascend- 

 ing order of their complication, assumed the character of 

 sciences; and will doubtless receive fresh confirmation from 

 those, of which the final scientific constitution is yet to come, 

 and which are still abandoned to the uncertainties of vague 

 and popular discussion. Although several other sciences have 

 emerged from this state at a comparatively recent date, none 

 now remain in it except those which relate to man himself, 



