TRAINS OF BEASONING. 137 



who resemble the observetl iiulividiuvls in the same attributes in which 

 lie resembles them ; that is (to express t,he thing concisely), of all men. 

 It" thert^tbre, the argument be conclusive in the case of Socrates, we 

 are at liberty, once for all, to treat the possession of tlie attributes of 

 man as a mark, or satisfactory evidence, of the attribute of mortality. 

 This we do by laying down tlie universal proposition. All men are 

 mortal, and interpreting this, as occasion arises, in its application to 

 Socrates and others. By this means we establish a very convenient 

 di\-ision of the jentire logical operation into two steps ; first, that of 

 ascertaining what attributes are marks of mortality ; and, secondly, 

 A\'hether any given individuals possess those marks. And it will, gener- 

 ally be ad\-isable, in our speculations on the reasoning process, to 

 consider this double operation as in fact taking place, and all rfeason- 

 ing as carried on in the form into which it must necessarily be thrown 

 to enable us to apply to it any test of its coiTect performance. 



Although, therefore, all processes of thought in which the ultimate 

 premisses are particulars, whether we conclude from particulars to a 

 general formula, or from particulars to other particulars according to 

 that formula, are equally Induction ; we shall yet, confonoiably to 

 usage, consider the name Induction as more peculiarly belonging to 

 the process of establishing the general proposition ; and the remaining 

 operation, which is substantially that of intei-}5reting the general pro- 

 position, we shall call by its usual name, Deduction. And we shall 

 consider every process by which anything is inferred respecting an 

 unobserved case, as consisting of an Induction followed by a Deduc- 

 tion ; because, although the process needs not necessarily be earned 

 on in this form, it is always susceptible of the form, and must be 

 thrown into it when assurance of scientific accuracy is needed and 

 desired. 



CHAPTER IV. 



OF TRAINS OF REASONING, AND DEDUCTIVE SCIENCES. 



§ 1. In our analysis of the syllogism it appeared that the minor prem- 

 iss always affirms a resemblance between a new case, and some cases 

 previously known ; while the major premiss asserts something which, 

 having been found true of those known cases, we consider ourselves 

 warranted in holding true of any other case resembling the former in 

 certain given particulars. 



If all ratiocinations resembled, as to the minor premiss, the examples 

 which we exclusively employed in the pi'eceding chapter; if the Te-~ 

 semblance, which that premiss asserts, were obvious to the senses, as in 

 the proposition, " Socrates is a man," or were at once ascertainable by 

 direct observation ; there would be no necessity for trains of reasoning, 

 and Deductive or Ratiocinative Sciences would not exist. Trains of 

 reasoning exist only for the sake of extending an induction, founded as 

 all inductions must be upon observed cases, to other cases in which we 

 not only cannot directly observe what is to be proved, but cannot di- 

 rectly observe even the mark which is to prove it. 

 S 



