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CHAPTER I. 

 INTRODUCTORY REMARKS. 



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 Scien- 

 tific 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 altogether, or if it 

 succeeded here and there in obtaining a solution, 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 attaining the 

 end is seen as it were instinctively by superior minds 

 in some comparatively 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 easy 

 ones. 



This truth is exemplified by the history of the 

 various branches of knowledge which have succes- 

 sively, in the ascending 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 



