SECT. 14.] Induction. 215 



butes, has an important bearing on the process of inference 

 which was indicated in the earlier sections of this chapter, 

 and which we must now examine in more special reference 

 to our particular subject. 



14. It will serve to bring out more clearly the nature 

 of some of those peculiarities of the step which we are now 

 about to take in the case of Probability, if we first examine 

 the form which the corresponding step assumes in the case 

 of ordinary Logic. Suppose then that we wished to ascertain 

 whether a certain John Smith, a man of thirty, who is 

 amongst other things a resident in India, and distinctly 

 affected with cancer, will continue to survive there for 

 twenty years longer. The terms in which the man is thus 

 introduced to us refer him to different classes in the way 

 already indicated. Corresponding to these classes there will 

 be a number of propositions which have been obtained by 

 previous observations and inductions, and which we may 

 therefore assume to be available and ready at hand when 

 we want to make use of them. Let us conceive them to 

 be such as these following : Some men live to fifty ; some 

 Indian residents live to fifty ; no man suffering thus from 

 cancer lives for five years. From the first and second of these 

 premises nothing whatever can be inferred, for they are both 1 

 particular propositions, and therefore lead to no conclusion 

 in this case. The third answers our enquiry decisively. 



To the logical reader it will hardly be necessary to point 

 out that the process here under consideration is that of 

 finding middle terms which shall serve to connect the 

 subject and predicate of our conclusion. This subject and 

 predicate in the case in question, are the individual before 



1 As particular propositions they corresponds to a larger proportion 

 are both of course identical in form. than in the latter, is a distinction 

 The fact that the some in the former alien to pure Logic. 



