INFERENCE IN GENERAL. 219 



though all water is liquid, it is not implied that all 

 liquid is water ; but it is implied that some liquid is 

 so ; and hence the proposition, All A is B, is legiti- 

 mately convertible into Some B is A. This process, 

 which converts an universal proposition into a parti- 

 cular, is termed conversion per accidens. From the 

 proposition, Some A is not B, we cannot even infer 

 that some B is not A : though some men are not 

 Englishmen, it does not follow that some Englishmen 

 are not men. The only legitimate conversion, if such 

 it can be called, of a particular negative proposition, 

 is in the form, Some A is not B, therefore, something 

 which is not B is A ; and this is termed conversion 

 by contraposition. In this case, however, the predi- 

 cate and subject are not merely reversed, but one of 

 them is altered. Instead of [A] and [B] , the terms 

 of the new proposition are [a thing which is not B] , 

 and [A], The original proposition, Some A is not'B, 

 is first changed into a proposition sequipollent with it, 

 Some A is " a thing which is not B ;" and the pro- 

 position, being now no longer a particular negative, 

 but a particular affirmative, admits of conversion in 

 the first mode, or, as it is called, simple conversion. 



In all these cases there is not really any inference; 

 there is in the conclusion no new truth, nothing but 

 what was already asserted in the premisses, and obvious 

 to whoever apprehends them. The fact asserted in 

 the conclusion is either the very same fact, or part of 

 the fact, asserted in the original proposition. This 

 follows from our previous analysis of the Import of 

 Propositions. When we say, for example, that some 

 lawful sovereigns are tyrants, what is the meaning of 

 the assertion ? That the attributes connoted by the 

 term " lawful sovereign," and the attributes connoted 

 by the term ct tyrant," sometimes coexist in the same 



