158 EEASONING. 



CHAPTER IV. 



OF TRAINS OF EEASOXING, 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 previous- 

 ly known ; while the major premise asserts something which, having been 

 found true of those known cases, we consider ourselves warranted in hold- 

 ing true of any other case resembling the former in certain given particu- 

 lars. 



If all ratiocinations resembled, as to thg minor premise, the examples 

 which were exclusively employed in the preceding chapter; if the resem- 

 blance, 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 Ratiocinative 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 can not di- 

 rectly observe the fact which is to be proved, but can not 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 conclu- 

 sion respecting the animal now present will be instantly 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 poisonous, the substance which is before me is arsenic, therefore it is poi- 

 sonous. The truth of the minor may not here be obvious at first sight; 

 it may not be intuitively evident, but may itself be known only by infer- 

 ence. It may be the conclusion of another argument, which, thrown into 

 the syllogistic form, would stand thus : Whatever when lighted produces 

 a dark spot on a piece of white porcelain held in the flame, which spot is 

 soluble in hypochloride of calcium, is arsenic; the substance before me con- 

 forms to this condition ; therefore it is arsenic. To establish, therefore, 

 the ultimate conclusion, The substance before me is poisonous, requires a 

 pi'ocess, which, in order to be syllogistically expressed, stands in need of 

 two syllogisms ; and we have a Train of Reasoning. 



When, however, we thus add syllogism to syllogism, we are really add- 

 ing induction to induction. Two separate inductions must have taken 

 place to render this chain of inference possible ; inductions founded, prob- 

 ably, on different sets of individual instances, but which converge in their 

 results, so that the instance which is the subject of inquiry comes within 

 the range of them both. The record of these inductions is contained in 

 the majors of the two syllogisms. First, we, or others for us, have exam- 

 ined various objects which yielded under the given circumstances a dark 



