FALLACIES OF GENERALIZATION. 375 



froth and straws floating on its surface, while more weighty 

 objects sink to the bottom; this, even if the assertion illus- 

 trated by it were true, would be no good illustration, there 

 being no parity of cause. The levity by which substances 

 float on a stream, and the levity which is synonymous with 

 worthlessness, have nothing^in common except the name ; and 

 (to show how little value there is in the metaphor) we need 

 only change the word into buoyancy, to turn the sem- 

 blance of argument involved in Bacon's illustration against 

 himself. 



A metaphor, then, is not to be considered as an argument, 

 but as an assertion that an argument exists ; that a parity 

 subsists between the case from which the metaphor is drawn 

 and that to which it is applied. This parity may exist 

 though the two cases be apparently very remote from one 

 another ; the only resemblance existing between them may be 

 a resemblance of relations, an analogy in Ferguson's and 

 Archbishop Whately's sense : as in the preceding instance, in 

 which an illustration from agriculture was applied to mental 

 cultivation. 



8. To terminate the subject of Fallacies of Generaliza- 

 tion, it remains to be said, that the most fertile source of them 

 is bad classification : bringing together in one group, and 

 under one name, things which have no common properties, or 

 none but such as are too unimportant to allow general propo- 

 sitions of any considerable value to be made respecting the 

 class. The misleading effect is greatest, when a word which 

 in common use expresses some definite fact, is extended by 

 slight links of connexion to cases in which that fact does not 

 exist, but some other or others, only slightly resembling it. 

 Thus Bacon,* in speaking of the Idola or Fallacies arising from 

 notions temere et intzqualiter a rebus abstracts, exemplifies them 

 by the notion of Humidum or Wet, so familiar in the physics 

 of antiquity and of the middle ages. "Invenietur verbum 

 istud, Humidum, nihil aliud quam nota confusa diversarum 



* Nov. Org. Aph. 60. 



