PREFACE. Vll 



On the subject of Induction, the task to be per- 

 formed was that of generalizing the modes of investi- 

 gating truth and estimating evidence, by which so 

 many important and recondite laws of nature have, 

 in the various sciences, been aggregated to the stock 

 of human knowledge. That this is not a task free 

 from difficulty may be presumed from the fact, that 

 even at a very recent period, eminent writers (among 

 whom it is sufficient to name Archbishop Whately, 

 and the author of a celebrated article on Bacon in 

 the Edinburgh Review) have not scrupled to pro- 

 nounce it impossible.* The author has endeavoured 

 to combat their theory in the manner in which 

 Diogenes confuted the sceptical reasonings against 

 the possibility of motion; remembering that Dio- 

 genes' argument would have been equally conclusive, 

 though his individual perambulations might not have 

 extended beyond the circuit of his own tub. 



"Whatever may be the value of what the author 

 has succeeded in effecting on this branch of his sub- 

 ject, it is a duty to acknowledge that for much of it 



* In the later editions of Archbishop Whately 's Logic, he states 

 his meaning to be, not that " rules" for the ascertainment of truths 

 by inductive investigation cannot be laid down, or that they may 

 not be " of eminent service," but that they " must always be com- 

 paratively vague and general, and incapable of being built up into 

 a regular demonstrative theory like that of the Syllogism." (Book 

 iv. ch. iv. 3.) And he observes, that to devise a system for this 

 purpose, capable of being " brought into a scientific form," would 

 be an achievement which " he must be more sanguine than scien- 

 tific who expects." (Book iv. ch. ii. 4.) To effect this, however, 

 being the express object of the portion of the present work which 

 treats of Induction, the words in the text are no overstatement of 

 the difference of opinion between Archbishop Whately and me on 

 the subject. 



