APPROXIMATE GENERALIZATIONS. 139 



science has really determined the universal laws of any 

 phenomenon., not only are those laws generally too 

 much encumbered with conditions to be adapted for 

 every-day use, but the cases which present themselves 

 in life are too complicated, and our decisions require 

 to be taken too rapidly, to admit of waiting till the 

 existence of a phenomenon can be proved by what 

 have been scientifically ascertained to be universal 

 marks of it. To be indecisive and reluctant to act, 

 because we have not evidence of a perfectly conclusive 

 character to act upon, is a defect sometimes incident 

 to scientific minds, but which, wherever it exists, 

 renders them unfit for practical emergencies. If we 

 would succeed in action, we must judge by indications 

 which, although they do not generally mislead us, 

 sometimes do; and must make up as far as possible for 

 the incomplete conclusiveness of any one indication, 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 forma- 

 tions contain fossils. The importance of this class of 



