OF ARTS AND SCIENCES : APRIL 9, 1867. 263 



Since it can never be requisite that a fact stated should also be 

 implied in order to justify a conclusion, every logical principle con- 

 sidered as a proposition will be found to be quite empty. Considered 

 as regulating the procedure of inference, it is determinate ; but 

 considered as expressing truth, it is nothing. It is on this account 

 that that method of investigating logic which works upon syllogistic 

 forms is preferable to that other, which is too often confounded with it, 

 which undertakes to enunciate logical principles. 



§ 4. Decomposition of Argument. 



Since a statement is not an argument for itself, no fact concluded 

 can be stated in any one premise. Thus it is no argument to say 

 All A is B ; ergo Some A is B. 



If one fact has such a relation to another that, if the former is true, 

 the latter is necessarily or probably true, this relation constitutes a 

 determinate fact ; and therefore, since the leading principle of a com- 

 plete argument involves no matter of fact, every complete argument 

 has at least two premises. 



Every conclusion may be regarded as a statement substituted for 

 either of its premises, the substitution being justified by the other 

 premises. Nothing is relevant to the other premises, except what is 

 requisite to justify this substitution. Either, therefore, these other 

 premises will by themselves yield a conclusion which, taken as a prem- 

 ise along with the first premise, justifies the final conclusion ; or else 

 some part of them, taken with the first premise, will yield a conclusion 



that every man is mortal. But if the judgment amounts merely to this, that the 

 argument in question belongs to some genus all under which are valid, then in one 

 sense it does, and in another it does not, contain a premise. It does in this sense, 

 that by an act of attention such a proposition may be shown to have been virtually 

 involved in it; it does not in this sense, that the person making the judgment did 

 not actually understand this premise to be contained in it. This I express by say- 

 ing that this proposition is contained in the leading principle, but is not laid down. 

 This manner of stating the matter frees us at once from all psychological perplexi- 

 ties ; and at the same time we lose nothing, since all that we know of thought is but 

 a reflection of what we know of its expression. 



These vague arguments are just such as alone are suitable to oratory or popular 

 discourse, and they are appropriate to no other; and this fact justifies the appella- 

 tion, "rhetorical argument." There is also authority for this use of the term. 

 " Complete" and " incomplete " are adjectives which I have preferred to "perfect" 

 and " imperfect," as being less misleading when applied to argument, although the 

 latter are the best when syllogism is the noun to be limited. 



