172 INDUCTION. 



Although, for these reasons, there is not yet extant a body of Induc- 

 tive Logic, scientifically constructed ; the materials for its construction 

 exist, widely scattered, but abundant : and the selection and arrange- 

 ment of those materials is a task with which intellects of the highest 

 order, possessed of the necessary acqviirements, have at length consent- 

 ed to occupy themselves. Within a few years three wa'iters, profoundly 

 versed in every branch of physical science, and not unaccustomed to 

 carry their speculations into still higher regions of knowledge, have 

 made attempts, of unequal but all of very great merit, towards the 

 creation of a Philosophy of Induction : Sir John Herschel, in his Dis- 

 course OH the Study of Natural Philosophy ; Mr. Whewell, in his His- 

 tory and Philosophy of the Inductive Sciences; and, greatest of all, 

 M. Auguste Comte, in his Cours de Philosophic Positive, a work which 

 only requires to be better known, to place its author in the very high- 

 est class of European thinkers. That the present writer does not 

 consider any of these philosophers, or even all of them together, to have 

 entirely accoinplished this important work, is implied in his attempting 

 to contribute something further towards its achievement ; but with his 

 comparatively imperfect knowledge of the various physical sciences, 

 the attempt would have been desperate unless the materials had 

 been brought together, and had undergone a partial elaboration, by 

 their more competent hands ; even if he could have dispensed with 

 the many important logical ideas and principles, for the first sugges- 

 tion of which he has been indebted to one or other of those writers. 



§ 2. For the pui-poses of the present inquiry. Induction may be de- 

 fined, the operation of discovering and proving general propositions. 

 It is true that (as already shown) the process of indirectly ascertaining in- 

 dividual facts, is as truly inductive as that by which we establish general 

 truths. But it is not a different kind of induction ; it is another form of the 

 very same process : since, on the one hand, generals are but collec- 

 tions of particulars, definite in kind but indefinite in number; and on the 

 other hand, whenever the evidence which we derive fi-om observation 

 of known cases justifies us in drawing an inference respecting even one 

 unknown case, we should on the same evidence be justified in drawing 

 a similar inference with respect to a whole class of cases. The infer- 

 ence either does not hold at all, or it holds in all cases of a certain de- 

 scription ; in all cases which, in certain definable respects, resemble 

 those we have observed. 



If these remarks are just ; if the principles and rules of inference are 

 the same whether we infer general propositions or individual facts ; it 

 follows that a complete logic of the sciences would be also a complete 

 logic of practical business and common life. Since there is no case of 

 legitimate inference from experience, in which the conclusion may not 

 legitimately be a general proposition ; an analysis of the process by 

 which general truths are arrived at, is virtually an analysis of all induc- 

 tion whatever. Whether we are inquiring into a scientific principle or 

 into an individual fact, and whether we proceed by experiment or by ra- 

 tiocination, every step in the train of inferences is essentially inductive, 

 and the legitimacy of the induction depends in both cases upon the same 

 conditions. 



True it is that in the case of the practical inquirer, who is endeavor- 

 ing to ascertain facts not for the purposes of science but for those of 



