CHAPTER IV. 



OF TRAINS OF REASONING, AND DEDUCTIVE SCIENCES. 



1. IN our analysis of the syllogism, 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, 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 premise, 

 the examples which were exclusively employed in the preceding 

 chapter ; if the resemblance, which that premise 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 De- 

 ductive or Batiocinative Sciences would not exist. Trains of 

 reasoning exist only for the sake of extending an induction 

 founded, as all inductions must be, on observed cases, to other 

 cases in which we not only cannot directly observe what is to 

 be proved, but cannot directly observe even the mark which is 

 to prove it. 



2. Suppose the syllogism to be, All cows ruminate, 

 the animal which is before me is a cow, therefore it ruminates. 

 The minor, if true at all, is obviously so : the only premise 

 the establishment of which requires any anterior process of 

 inquiry, is the major ; and provided the induction of which 

 that premise is the expression was correctly performed, the 

 conclusion respecting the animal now present will be in- 

 stantly drawn ; because, as soon as she is compared with the 

 formula, she will be identified as being included in it. But 

 suppose the syllogism to be the following: All arsenic is 



