FUNCTIONS AND VALUE OF THE SYLLOGISM. 203 



of the syllogism to its legitimate corollary, have been led to 

 impute uselessness and frivolity to the syllogistic theory itself, 

 on the ground of the petitio principii which they allege to be 

 inherent in every syllogism. As I believe both these opinions 

 to be fundamentally erroneous, I must request the attention 

 of the reader to certain considerations, without which any just 

 appreciation of the true character of the syllogism, and the 

 functions it performs in philosophy, appears to me impossible ; 

 but which seem to have been either overlooked, or insufficiently 

 adverted to, both by the defenders of the syllogistic theory and 

 by its assailants. 



2. It must be granted that in every syllogism, con- 

 sidered as an argument to prove the conclusion, there is a 

 petitio principii. When we say, 



All men are mortal, 

 Socrates is a man, 



therefore 

 Socrates is mortal ; 



it is unanswerably urged by the adversaries of the syllogistic 

 theory, that the proposition, Socrates is mortal, is presupposed 

 in the more general assumption, All men are mortal : that we 

 cannot be assured of the mortality of all men, unless we are 

 already certain of the mortality of every individual man : that 

 if it be still doubtful whether Socrates, or any other individual 

 we choose to name, be mortal or not, the same degree of un- 

 certainty must hang over the assertion, All men are mortal : 

 that the general principle, instead of being given as evidence 

 of the particular case, cannot itself be taken for true without 

 exception, until every shadow of doubt which could affect any 

 case comprised with it, is dispelled by evidence aliunde ; and 

 then what remains for the syllogism to prove? That, in 

 short, no reasoning from generals to particulars can, as such, 

 prove anything : since from a general principle we cannot 

 infer any particulars, but those which the principle itself 

 assumes as known. 



This doctrine appears to me irrefragable ; and if logicians, 



