156 INDUCTION. 



But what can these evidences be ? Other phenomena ; 

 ascertained by induction to be connected with the 

 given phenomenon, either in the way of succession or 

 of coexistence. The simple existence, therefore, of 

 an individual phenomenon, when not directly per- 

 ceived, is inferred from some inductive law of succes- 

 sion or coexistence : and is consequently not amenable 

 to any peculiar inductive principles. We prove the 

 existence of a thing, by proving that it is connected by 

 succession or coexistence with some known thing. 



With respect to general propositions 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 generalizations 

 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 capable 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 proceed to the remaining two of the great classes 

 into which facts have been divided ; Resemblance, and 

 Order in Space. 



2. Resemblance and its opposite, except in the 

 case in which they assume the names of Equality and 

 Inequality, are seldom regarded as subjects of science ; 

 they are supposed to be perceived by simple appre- 

 hension ; by merely applying our senses or directing 

 our attention to the two objects at once, or in imme- 

 diate succession. And this simultaneous or virtually 

 simultaneous application of our faculties to the two 



