THE TEST OF TRUTH 



The primary axiom that a thing cannot both be 

 and not be at the same time known as the prin 

 ciple of contradiction or, as Sir William Hamil 

 ton preferred, of non-contradiction is a truth of 

 the highest certainty, because one cannot conceive 

 its negation. Thus the philosophy of Hegel is 

 founded upon a proposition that being and 

 not-being are the same which it is impossible to 

 conceive. But if one cannot conceive it, can one 

 imagine it? I trow not. That two and two are 

 four is similarly despite the dictum of Mill a 

 truth of the highest certainty, because one cannot 

 conceive its negation. The objector might an 

 swer with a case within my own experience, of a 

 man who believed that two and two are four and 

 a quarter, and whom no arguments could convince 

 of his error. But would I be entitled to say that 

 my friend could conceive the negation of the propo 

 sition that two and two are four? Surely I was 

 right in thinking that he was obsessed by a pseud- 

 idea an idea of which the elements, as Spen 

 cer says, &quot;cannot be combined in consciousness.&quot; 

 And I maintain the truth of my judgment by ob 

 serving that my friend never did really combine 

 the ideas of two and two so as to make them four 

 and a quarter. His idea was thus imaginable if 

 we are to use that word but not conceivable: any 

 more than the idea of a moral fluid or a square 

 idea is a conception. And, as a matter of fact, I 

 made my friend s acquaintance in a lunatic asylum. 

 This, curiously enough, was his one delusion. 



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