39^ 



INDUCTION. 



or in the senate-house at Rome. When 

 I believe that stars exist beyond the 

 utmost range of my vision, though 

 assisted by the most powerful tele- 

 scopes yet invented, my belief, philo- 

 sophically expressed, is, that with still 

 better telescopes, if such existed, I 

 could see them, or that they may be 

 perceived by beings less remote from 

 them in space, or whose capacities of 

 perception are superior to mine. 



The existence, therefore, of a pheno- 

 menon is but another word for its 

 being perceived, or for the inferred 

 possibility of perceiving it. When 

 the phenomenon is within the range 

 of present observation, by present ob- 

 servation we assure ourselves of its 

 existence ; when it is beyond that 

 range, and is therefore said to be 

 absent, we infer its existence from 

 marks or evidences. But what can 

 these evidences be? Other pheno- 

 mena, ascertained by induction to be 

 connected with the given phenome- 

 non, either in the way of succession 

 or of co-existence. The simple exist- 

 ence, therefore, of an individual pheno- 

 menon, when not directly perceived, 

 is inferred from some inductive law 

 of succession or co-existence, and is 

 consequently not amenable to any 

 peculiar inductive principles. We 

 prove the existence of a thing by 

 proving that it is connected by suc- 

 cession or co-existence with some 

 known thing. 



With respect to general proposi- 

 tions of this class, that is, which 

 affirm the bare fact of existence, they 

 have a peculiarity which renders the 

 logical treatment of them a very 

 easy matter ; they are generalisa- 

 tions which are sufficiently proved 

 by a single instance. That ghosts, 

 or unicorns, or sea-serpents exist, 

 would be fully established if it could 

 be ascertained positively that such 

 things had been even once seen. 

 Whatever has once happened is cap- 

 able of happening again ; the only 

 question relates to the conditions 

 under which it happens. 



So far, therefore, as relates to simple 



existence, the Inductive Logic has no 

 knots to untie. And we may pro- 

 ceed to the remaining two of the great 

 classes into which facts have been 

 divided ; Resemblance, and Order in 

 Place. 



§ 2. Resemblance and its opposite, 

 except in the case in which they as- 

 sume the names of Equality and In- 

 equality, are seldom regarded as sub- 

 jects of science ; they are supposed 

 to be perceived by simple apprehen- 

 sion ; by merely applying our senses 

 or directing our attention to the two 

 objects at once, or in immediate suc- 

 cession. And this simultaneous, or 

 virtually simultaneous application of 

 our faculties to the two things which 

 are to be compared, does necessarily 

 constitute the ultimate, appeal, wher- 

 ever such application is practical. 

 But, in most cases, it is not practi- 

 cable : the objects cannot be brought 

 so close together that the feeling of 

 their resemblance (at least a complet*; 

 feeling of it) directly arises in the 

 mind. We can only compare each o: 

 them with some third object, capabh 

 of being transported from one to th( 

 other. And besides, even when tht 

 objects can be brought into immediate 

 juxtaposition, their resemblance oi 

 difference is but imperfectly known 

 to us, unless we have compared them 

 minutely, part by part. Until this 

 has been done, things in reality very 

 dissimilar often appear undistinguish- 

 ably alike. Two lines of very unequal 

 length will appear about equal when 

 lying in different directions ; but 

 place them parallel with their farther 

 extremities even, and if we look at 

 the nearer extremities, their inequality 

 becomes a matter of direct perception. 



To ascertain whether, and in what, 

 two phenomena resemble or differ is 

 not always, therefore, so easy a thing 

 as it might at first appear. When 

 the two cannot be brought into juxta- 

 position, or not so that the observer 

 is able to compare their several parts 

 in detail, he must employ the indirect 

 means of reasoning and general pro- 



