126 INDUCTION. 



generally mislead us, sometimes do ; and must make up, as far 

 as possible, for the incomplete conclusiveness of any one indi- 

 cation, by obtaining others to corroborate it. The principles 

 of induction applicable to approximate generalization are 

 therefore a not less important subject of inquiry, than the 

 rules for the investigation of universal truths; and might 

 reasonably be expected to detain us almost as long, were it not 

 that these principles are mere corollaries from those which 

 have been already treated of. 



3. There are two sorts of cases in which we are forced 

 to guide ourselves by generalizations of the imperfect form, 

 Most A are B. The first is, when we have no others; when 

 we have not been able to carry our investigation of the laws of 

 the phenomena any farther ; as in the following propositions : 

 Most dark-eyed persons have dark hair ; Most springs contain 

 mineral substances ; Most stratified formations contain fossils. 

 The importance of this class of generalizations is not very 

 great ; for, though it frequently happens that we see no reason 

 why that which is true of most individuals of a class is not true 

 of the remainder, nor are able to bring the former under any 

 general description which can distinguish them from the latter, 

 yet if we are willing to be satisfied with propositions of a less 

 degree of generality, and to break down the class A into sub- 

 classes, we may generally obtain a collection of propositions 

 exactly true. We do not know why most wood is lighter than 

 water, nor can we point out any general property which discri- 

 minates wood that is lighter than water from that which is 

 heavier. But we know exactly what species are the one and 

 what the other. And if we meet with a specimen not con- 

 formable to any known species (the only case in which our 

 previous knowledge affords no other guidance than the ap- 

 proximate generalization), we can generally make a specific 

 experiment, which is a surer resource. 



It often happens, however, that the proposition, Most A 

 are B, is not the ultimatum of our scientific progress, though 

 the knowledge we possess beyond it cannot conveniently be 

 brought to bear upon the particular instance. In such a case 



