SOME LOGICAL IMPOSSIBILITIES 



By CHARLES A. MERCIER, M.D., F.R.C.P. 



"There are impossibilities logical, but none natural." This 

 quotation from Huxley in Mr. Hill's article in the April number 

 of Science Progress is a capital instance of the equivocation of 

 terms. There are logical impossibilities and logical impossi- 

 bilities. Some, such as a round square or a present past, are 

 truly impossible ; but there is a huge class of " logical impossi- 

 bilities " that are impossibilities only in the sense that logicians 

 declare that they are impossible, but that are, in fact, surmount- 

 able with ease, not only by the non-logical public, but also by 

 logicians themselves when they forget, as they often do, that 

 they have declared them impossible. It was said by the late 

 Lord Salisbury that certain politicians seem to live in a balloon, 

 so oblivious are they of the actual state of affairs with which 

 they have to cope. Logicians may be said in this sense to live 

 in a balloon ; for not only do they profess ignorance of the 

 ways in which other people are accustomed to perform their 

 reasonings, but also they declare that these ways are impossible. 

 It is impossible, they say, to walk, for are we not cooped up in 

 a little basket, in which there is no room to use the legs ? In 

 vain we, who are not logicians, point out that every one does 

 not live in a balloon, and that the earth beneath is quite large 

 enough to walk about on. The answer of the logician is con- 

 clusive. My balloon, he says, is the only means of locomotion; 

 it is the only way of getting from place to place ; and any one 

 who attempts any other mode of locomotion will immediately 

 lose his way, and be bogged in the slough of fallacy. It makes 

 not the slightest impression on him that no one in practice 

 adopts his means of locomotion, and that he himself, when he 

 is out of his balloon — his book on Logic — uses his legs and 

 walks about like other people. He still holds, and asserts with 

 the confidence of infallibility, that it is impossible to get from 

 place to place except by balloon — that it is impossible to get 

 from premisses to conclusion except by the methods of Logic. 



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