194 OPERATIONS SUBSIDIARY TO INDUCTION. 



Mill) the idea of the class is that of a miscellaneous assemblage 

 of individuals belonging to the class ; or whether, finally, (what 

 appears to be the truest opinion,) it be any one or any other 

 of all these, according to the accidental circumstances of the 

 case ; certain it is, that some idea or mental conception is sug 

 gested by a general name, whenever we either hear it or employ 

 it with consciousness of a meaning. And this, which we may 

 call if we please a general idea, represents in our minds the 

 whole class of things to which the name is applied. Whenever 

 we think or reason concerning the class, we do so by means of 

 this idea. And the voluntary power which the mind has, of 

 attending to one part of what is present to it at any moment, 

 and neglecting another part, enables us to keep our reasonings 

 and conclusions respecting the class unaffected by anything 

 in the idea or mental image which is not really, or at least which 

 we do not really believe to be, common to the whole class.* 



There are, then, such things as general conceptions, or 

 conceptions by means of which we can think generally : and 

 when we form a set of phenomena into a class, that is, when 

 we compare them with one another to ascertain in what they 

 agree, some general conception is implied in this mental opera 

 tion. And inasmuch as such a comparison is a necessary pre 

 liminary to Induction, it is most true that Induction could not 

 go on without general conceptions. 



2. But it does not therefore follow that these general 

 conceptions must have existed in the mind previously to the 

 comparison. It is not a law of our intellect, that in com 

 paring things with each other and taking note of their agree 

 ment we merely recognise as realized in the outward world 

 something that we already had in our minds. The con 

 ception originally found its way to us as the result of such a 

 comparison. It was obtained (in metaphysical phrase) by 

 abstraction from individual things. These things may be 

 things which we perceived or thought of on former occasions, 



* I have entered rather fully into this question in chap. xvii. of An Exami 

 nation of Sir William, Hamilton s Philosophy, headed &quot; The Doctrine of Con 

 cepts or General Notions,&quot; which contains my last views on the subject. 



