650 SCIENCE PROGRESS 



" Logic takes no cognisance of the truth or falsehood of a 

 premiss." This is true of deductive Logic only. To inductive 

 Logic the truth of the premiss is vital. 



I pass Mr. Winter's examination of my arguments. It 

 does not touch their validity in the least, as any competent 

 reasoner can see for himself. I am indebted to him for one 

 discovery, however. Until I read his rejoinder, I was con- 

 vinced that professional logicians are the very worst reasoners 

 in the world. I must now revise this opinion, for it is evident 

 that Mr. Winter has very little acquaintance with Logic " as 

 she is taught." 



I am, Sir, your obedient servant, 



Chas. A. Mercier. 



II. Reply: By W. H. Winter, B.A. (Camb.), M.A. 



(St. Andrews) 



Sir, — I am obliged for your courtesy in sending me a copy of 

 Dr. Mercier 's reply to my criticism. 



A considerable part of it is taken up with representing me 

 as saying precisely the contrary of what I did say. Example 

 Q I gave as an illustration of immediate inference as dis- 

 tinguished from argument. Neither P nor Q is an argument. 

 An argument when stated in its complete form will be found 

 to consist of two premisses and a conclusion. It is true that 

 in practice one premiss is frequently suppressed, especially if 

 it is regarded as a matter of common knowledge. This was 

 the case in Dr. Mercier's horticultural example. The minor 

 premiss, No geranium or viola is an aster, was not expressed, 

 but tacitly taken for granted as a known fact. It is none the 

 less vital to the reasoning, for, if either the geranium or the 

 viola were a species of aster, the conclusion would obviously 

 be invalid. Dr. Mercier quotes my test for an argument that 

 it should contain a conclusion which is not specifically implied 

 in a premiss, and characterises it as the reverse of the truth. 

 Surely this is the limit of absurdity. Unless you gain some 

 fresh point when you argue, what is the use of arguing ? If 

 Dr. Mercier really wants to know what an argument is, let him 

 renew his acquaintance with Euclid's Elements. He will there 

 find a book full of arguments from beginning to end, and I 

 believe on investigation he will discover every one of them 



