INFERENCE IN GENERAL. 177 



2. In proceeding to take into consideration the cases 

 in which inferences can legitimately be drawn, we shall first 

 mention some cases in which the inference is apparent, not 

 real ; and which require notice chiefly that they may not be 

 confounded with cases of inference properly so called. This 

 occurs when the proposition ostensibly inferred from another, 

 appears on analysis to be merely a repetition of the same, or 

 part of the same, assertion, which was contained in the first. 

 All the cases mentioned in books of Logic as examples of 

 aequipollency or equivalence of propositions, are of this nature. 

 Thus, if we were to argue, No man is incapable of reason, 

 for every man is rational ; or, All men are mortal, for no 

 man is exempt from death ; it would be plain that we were 

 not proving the proposition, but only appealing to another 

 mode of wording it, which may or may not be more readily 

 comprehensible by the hearer, or better adapted to suggest 

 the real proof, but which contains in itself no shadow of 

 proof. 



Another case is where, from an universal proposition, we 

 affect to infer another which differs from it only in being par- 

 ticular : as All A is B, therefore Some A is B : No A is B, 

 therefore Some A is not B. This, too, is not to conclude one 

 proposition from another, but to repeat a second time some- 

 thing which had been asserted at first; with the difference, 

 that we do not here repeat the whole of the previous assertion, 

 but only an indefinite part of it. 



A third case is where, the antecedent having affirmed a 

 predicate of a given subject, the consequent affirms of the 

 same subject something already connoted by the former pre- 

 dicate : as, Socrates is a man, therefore Socrates is a living 

 creature; where all that is connoted by living creature was 

 affirmed of Socrates when he was asserted to be a man. 

 If the propositions are negative, we must invert their order, 

 thus : Socrates is not a living creature, therefore he is not a 

 man ; for if we deny the less, the greater, which includes it, 

 is already denied by implication. These, therefore, are not 

 really cases of inference ; and yet the trivial examples by 

 which, in manuals of Logic, the rules of the syllogism are 

 VOL. i. 12 



