APPROXIMATE GENERALIZATION S. 129 



not ; we are rather more favourably situated than in the pre 

 ceding case. For we have now a double mode of ascertaining 

 whether it be true that most A are B ; the direct mode, as 

 before, and an indirect one, that of examining whether the 

 proposition admits of being deduced from the known cause, or 

 from any known criterion, of B. Let the question, for example, 

 be whether most Scotchmen can read ? We may not have 

 observed, or received the testimony of others respecting, a suf 

 ficient number and variety of Scotchmen to ascertain this fact ; 

 but when we consider that the cause of being able to read is 

 the having been taught it, another mode of determining the 

 question presents itself, namely, by inquiring whether most 

 Scotchmen have been sent to schools where reading is effec 

 tually taught. Of these two modes, sometimes one and some 

 times the other is the more available. In some cases, the fre 

 quency of the effect is the more accessible to that extensive and 

 varied observation which is indispensable to the establishment 

 of an empirical law ; at other times, the frequency of the causes, 

 or of some collateral indications. It commonly happens 

 that neither is susceptible of so satisfactory an induction as 

 could be desired, and that the grounds on which the conclu 

 sion is received are compounded of both. Thus a person may 

 believe that most Scotchmen can read, because, so far as his 

 information extends, most Scotchmen have been sent to 

 school, and most Scotch schools teach reading effectually; and 

 also because most of the Scotchmen whom he has known or 

 heard of, could read; though neither of these two sets of ob 

 servations may by itself fulfil the necessary conditions of ex 

 tent and variety. 



Although the approximate generalization may in most cases 

 be indispensable for our guidance, even when we know the 

 cause, or some certain mark, of the attribute predicated; it 

 needs hardly be observed that we may always replace the 

 uncertain indication by a certain one, in any case in which we 

 can actually recognise the existence of the cause or mark. 

 For example, an assertion is made by a witness, and the 

 question is, whether to believe it. If we do not look to any 

 of the individual circumstances of the case, we have nothing 

 VOL. ii. 9 



