392 FALLACIES. 



One of the most singular examples of the length to which 

 a thinker of eminence may be led away by an ambiguity of 

 language, is afforded by this very case. I refer to the famous 

 argument by which Bishop Berkeley flattered himself that he 

 had for ever put an end to &quot; scepticism, atheism, and irre- 

 ligion.&quot; It is briefly as follows. I thought of a thing yester 

 day; I ceased to think of it; I think of it again to-day. I 

 had, therefore, in my mind yesterday an idea of the object ; 

 I have also an idea of it to-day ; this idea is evidently not 

 another, but the very same idea. Yet an intervening time 

 elapsed in which I had it not. Where was the idea during 

 this interval ? It must have been somewhere ; it did not 

 cease to exist ; otherwise the idea I had yesterday could not 

 be the same idea ; no more than the man I see alive to-day 

 can be the same whom I saw yesterday, if the man has died 

 in the meanwhile. Now an idea cannot be conceived to exist 

 anywhere except in a mind ; and hence there must exist an 

 Universal Mind, in which all ideas have their permanent 

 residence, during the intervals of their conscious presence in 

 our own minds. 



It is evident that Berkeley here confounded sameness 

 numero with sameness specie, that is, with exact resemblance, 

 and assumed the former where there was only the latter ; not 

 perceiving that when we say we have the same thought to-day 

 which we had yesterday, we do not mean the same individual 

 thought, but a thought exactly similar : as we say that we 

 have the same illness which we had last year, meaning only 

 the same sort of illness. 



In one remarkable instance the scientific world was 

 divided into two furiously hostile parties by an ambiguity of 

 language affecting a branch of science which, more completely 

 than most others, enjoys the advantage of a precise and well- 

 defined terminology. I refer to the famous dispute respecting 

 the vis viva, the history of which is given at large in Professor 

 Playfair s Dissertation. The question was, whether the force 

 of a moving body was proportional (its mass being given) to 

 its velocity simply, or to the square of its velocity : and the 

 ambiguity was in the word Force. &quot; One of the effects,&quot; says 



