SECT. 12.] Induction. 213 



task ? In the former case our data were of this kind : 

 Eight out of ten men, aged fifty, will live eleven years more, 

 and we ascertained in what sense, and with what certainty, 

 we could infer that, say, John Smith, aged fifty, would live 

 to sixty-one. 



12. Let us then suppose, instead, that John Smith 

 presents himself, how should we in this case set about ob 

 taining a series for him ? In other words, how should we 

 collect the appropriate statistics? It should be borne in 

 mind that when we are attempting to make real inferences 

 about things as yet unknown, it is in this form that the 

 problem will practically present itself. 



At first sight the answer to this question may seem to be 

 obtained by a very simple process, viz. by counting how 

 many men of the age of John Smith, respectively do and do 

 not live for eleven years. In reality however the process is 

 far from being so simple as it appears. For it must be re 

 membered that each individual thing has not one distinct 

 and appropriate class or group, to which, and to which alone, 

 it properly belongs. We may indeed be practically in the 

 habit of considering it under such a single aspect, and it may 

 therefore seem to us more familiar when it occupies a place 

 in one series rather than in another ; but such a practice is 

 merely customary on our part, not obligatory. It is obvious 

 that every individual thing or event has an indefinite 

 number of properties or attributes observable in it, and 

 might therefore be considered as belonging to an indefinite 

 number of different classes of things. By belonging to any 

 one class it of course becomes at the same time a member of 

 all the higher classes, the genera, of which that class was a 

 species. But, moreover, by virtue of each accidental attri 

 bute which it possesses, it becomes a member of a class 

 intersecting, so to say, some of the other classes. John Smith 



