XXXIX.] MENTAL INTELLIGENCE. 159 



universal and necessary truth of this logical principle. These are 

 Indeed, the argument is stronger for the belief in the iui- \^^^^ ^^' 

 possibility of a contradiction being independent of expe- gence 

 rience and antecedent to it, than for the belief in the order habit. 

 of nature being independent of experience ; for our belief 

 in the order of nature is merely that it is and will be 

 constant, so long as no cause occurs to disturb it ; but 

 our belief in the impossibility of a contradiction is without 

 any such qualification ; under no circumstances, and in 

 no world, can it ever be possible for a contradiction to be 

 true. This belief, I think, cannot be the result of habit, 

 and can only belong to intelligence. 



Further : I maintain that the perception of things ex- 

 ternal to ourselves is an inference from our sensations. It 

 is obvious that, once the idea of an external world has 

 been suggested to us, the belief in its existence receives 

 confirmation at every moment. But what first suggested 

 the idea of an external world ? The process of inference They are 

 involved in perception may be thus expressed :— =-" This iii^olved 



■^ ^ . *' . . -^ . lu percep- 



sensation has not its source within me ; it must there- tion. 

 fore have its source outside of me." This is obviously The logical 

 a particular application of the law that a contradiction of identity, 

 cannot be true ; for it would be a contradiction if the 

 source were at once within and without. 



But this is not a full account of the subject : for, why 

 do we take for granted that sensations must have a source 

 at all ? or, in other words, why do we refer sensations to 

 their objects ? This is only a particular way of asking the 

 question, what is the nature and meaning of our idea of The 

 substance? Mr. Mill defines matter as a "permanent ^'^^^"^ 



^ substance. 



possibility of sensation : " which is obviously true, but, I 

 think, inadequate as a definition ; just as it would be an 

 inadequate definition of the mind, or the conscious self, to 

 call it a permanent liability to sensations and other feel- 

 ings.^ In becoming conscious of our own feelings, we 



1 Mr. Mill (Examination of Sir William Hamilton's Philosophy) defines 

 matter as " a permanent possibility of sensation ;" but he goes on to pay 

 (though not in these words) that it would not be an adequate definition of 



