388 INDUCTION. 



incomplete conclusiveness of any one 

 indication, by obtaining others to 

 corroborate it. The principles of 

 induction applicable to approximate 

 generalisation are therefore a not less 

 important subject of inquiry than 

 the rules for the investigation of uni- 

 versal 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 our- 

 selves by generalisations of the im- 

 perfect 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 generalisations 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 dis- 

 tinguish them from the latter, yet if 

 we are willing to be satisfied with 

 propositions of a less degree of gene- 

 rality, 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 pro- 

 perty which discriminates 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 conformable to any 

 known species, (the only case in which 

 our previous knowledge affords no 

 other guidance than the approximate 

 generalisation,) we can generally make 

 a specific experiment, which is $1 surer 

 ^resource, 



It often happens, however, that th« 

 proposition, Most A are B, is not th« 

 ultimatum of our scientific attain- 

 ments, though the knowledge we pos- 

 sess beyond it cannot conveniently b« 

 brought to bear upon the particular 

 instance. We may know well enough 

 what circumstances distinguish the 

 portion of A which has the attribute 

 B from the portion which has it not, 

 but may have no means, or may not 

 have time to examine whether those 

 characteristic circumstances exist or 

 not in the individual case. This is 

 the situation we are generally in when 

 the inquiry is of the.kind called moral, 

 that is, of the kind which has in view 

 to predict human actions. To enable 

 us to affirm anj^hing universally con- 

 cerning the actions of classes of hu- 

 man beings, the classification must 

 be grounded on the circumstances of 

 their mental culture and habits, which 

 in an individual case are seldom ex- 

 actly known ; and classes grounded 

 on these distinctions would never 

 precisely accord with those into which 

 mankind are divided for social pur- 

 poses. All propositions which can 

 be framed respecting the actions of 

 human beings as ordinarily classified, 

 or as classified according to any kind 

 of outward indications, are merely 

 approximate. We can only say. Most 

 persons of a particular age, profes- 

 sion, country, or rank in society have 

 such and such qualities ; or. Most 

 persons when placed in certain cir- 

 cumstances act in such and such a 

 way. Not that we do not often know 

 well enough on what causes the quali- 

 ties depend, or what sort of persons 

 they are who act in that particular 

 way ; but we have seldom the means 

 of knowing whether any individual 

 person has been under the influence 

 of those causes, or is a person of that 

 particular sort. We could replace 

 the approximate generalisations by 

 propositions universally true ; but 

 these would hardly ever be capable 

 of being applied to practice. We 

 should be sure of our majors, but we 

 should not be able to get minora to 



