TRAINS OF REASONING. 



137 



whole of Logic properly so called, is 

 really a very subordinate part of it, 

 not being directly concerned with the 

 process of Reasoning or Inference in 

 the sense in which that process is a 

 part of the Investigation of Truth. 

 What, then, is I ormal Logic ? The 

 name seems to be properly applied to 

 all that portion of doctrine which re- 

 lates to the equivalence of different 

 modes of expression ; the rules for 

 determining when assertions in a 

 given form imply or suppose the truth 

 or falsity of other assertions. This 

 includes the theory of the Import of 

 Propositions, and of their Conversion, 

 iEquipollence, and Opposition : of 

 those falsely called Inductions (to be 

 hereafter spoken of *), in which the 

 apparent generalisation is a mere 

 abridged statement of cases known 

 individually ; and finally, of the syl- 

 logism : while the theory of Naming, 

 and of (what is inseparably connected 



against erroneous reasoning. The only 

 minor premise necessary to reasoning in 

 the example under consideration is, Soc- 

 i-ates is like A, B, C, and the other indi- 

 viduals who are known to have died. And 

 this is the only universal type of that step 

 in the reasoning process which is repre- 

 sented by the minor. Experience, how- 

 ever, of the uncertainty of this loose mode 

 of inference teaches the exi)ediency of de- 

 termining beforehand wliat kind of likeness 

 to the cases observed is necessary to bring 

 an unobserved case within the same predi- 

 cate ; and the answer to this question is 

 the major. The minor then identifies the 

 precise kind of likeness possessed by Soc- 

 rates, as being the kind required by the 

 formula. Thus the syllogistic mrijor and 

 the syllogi.stic minor start into existence 

 together, and are called forth by the same 

 exigency. When we conclude from per- 

 sonal experience without referring to any 

 record— to any general theorems, either 

 written, or traditional, or mentally regis- 

 tered by ourselves as conclusions of our 

 own drawing — we do not use, in our 

 thoughts, either a major or a minor, such 

 as the syllogism puts into words. When, 

 however, we revise this rough inference 

 from particulars to particulars, and substi- 

 tute a careful one, the revision consists in 

 selectiner two syllogistic premises. But 

 this neither alters nor adds to the evidence 

 we had before ; it only puts us in a better 

 position for judging whether our inference 

 from particulars to particulars ia well 

 grounded. 

 * Infra, book iii. ch. ii. 



with it) Definition, though belonging 

 still more to the other and larger kind 

 of logic than to this, is a necessary 

 preliminary to this. The end aimed 

 at by Formal Logic, and attained by 

 the observance of its precepts, is not 

 truth, but consistency. It has been 

 seen that this is the only direct pur- 

 pose of the rules of the syllogism ; 

 the intention and effect of which is 

 simply to keep our inferences or con- 

 clusions in complete consistency with 

 our general formulae or directions for 

 drawing them. The Logic of Con- 

 sistency is a necessary auxiliary to 

 the Logic of Truth, not only because 

 what is inconsistent with itself or with 

 other truths cannot be true, but also 

 because truth can only be successfully 

 pursued by drawing inferences from 

 experience, which, if warrantable at 

 all, admit of being generalised, and, 

 to test their warrantableness, require 

 to be exhibited in a generalised form ; 

 after which the correctness of their 

 application to particular cases is a 

 question which specially concerns the 

 Logic of Consistency. This Logic, 

 not requiring any preliminary know- 

 ledge of the processes or conclusions 

 of the various sciences, may be studied 

 with benefit in a much earlier stage 

 of education than the Logic of Truth : 

 and the practice which has empirically 

 obtained of teaching it apart, through 

 elementary treatises which do not 

 attempt to include anything else, 

 though the reasons assigned for the 

 practice are in general very far from 

 philosophical, admits of philosophical 

 justification. 



CHAPTER IV. 



OF TRAINS OP REASONING AND 

 DEDUCTIVE SCIENCES. 



§ I. In our analysis of the syl- 

 logism, it appeared that the minor 

 premise always affirms a resemblance 

 between a new case and some cases 

 previously known ; while the major 

 premise asserts something which, 



