OF NATURAL PHILOSOPHY. 165 



almost all our principal inductions must be regarded 

 as a series of ascents and descents, and of conclusions 

 from a few cases, verified by trial on many. 



(172.) Whenever, therefore, we think we have 

 been led by induction to the knowledge of the proxi- 

 mate cause of a phenomenon or of a law of nature, our 

 next business is to examine deliberately and seriatim 

 all the cases we have collected of its occurrence, in 

 order to satisfy ourselves that they are explicable 

 by our cause, or fairly included in the expression 

 of our law : and in case any exception occurs, it must 

 be carefully noted and set aside for re-examination 

 at a more advanced period, when, possibly, the cause 

 of exception may appear, and the exception itself, 

 by allowing for the effect of that cause, be brought 

 over to the side of our induction ; but should ex- 

 ceptions prove numerous and various in their fea- 

 tures, our faith in the conclusion will be propor- 

 tionally shaken, and at all events its importance 

 lessened by the destruction of its universality. 



(173.) In the conduct of this verification, we are to 

 consider whether the cause or law to which we are 

 conducted be one already known and recognised as 

 a more general one, whose nature is well understood, 

 and of which the phenomenon in question is but one 

 more case in addition to those already known, or 

 whether it be one less general, less known, or alto- 

 gether new. In the latter case, our verification will 

 suffice, if it merely shows that all the cases con- 

 sidered are plainly cases in point. But in the 

 former, the process of verification is of a much more 

 severe and definite kind. We must trace the action 

 of our cause with distinctness and precision, as modi- 

 M 3 



