388 INDUCTION. 



uniformity, therefore, may be presumed, from any 

 given number of instances, with a greater degree of 

 assurance, in proportion as the case belongs to a class 

 in which the uniformities have hitherto been found 

 more uniform. 



This mode of correcting one generalization by 

 means of another, a narrower generalization by a 

 wider, which common sense suggests and adopts in 

 practice, is the real type of scientific Induction. All 

 that art can do is but to give accuracy and precision 

 to this process, and adapt it to all varieties of cases, 

 without any essential alteration in its principle. 



There are of course no means of applying such a 

 test as that above described, unless we already possess 

 a general knowledge of the prevalent character of the 

 uniformities existing throughout nature. The indis- 

 pensable foundation, therefore, of a scientific formula of 

 induction, must be a survey of the inductions to which 

 mankind have been conducted in unscientific practice ; 

 with the special purpose of ascertaining what kinds 

 of uniformities have been found perfectly invariable, 

 pervading all nature, and what are those which have 

 been found to vary with difference of time, place, or 

 other changeable circumstances. 



$ 3. The necessity of such a survey is confirmed 

 by the consideration, that the stronger inductions are 

 the touchstone to which we always endeavour to bring 

 the weaker. If we find any means of deducing one 

 of the less strong inductions from stronger ones, 

 it acquires, at once, all the strength of those from 

 which it is deduced ; and even adds to that strength ; 

 since the independent experience on which the 

 weaker induction previously rested, becomes addi- 

 tional evidence of the truth of the better esta- 



