558 FALLACIES. 



states it in terms which, by suggesting a parallel case, put the mind upon 

 the track of the real proof. For, the reason why weeds grow in an uncul- 

 tivated soil, is that the seeds of worthless products exist everywhere, and 

 can germinate and grow in almost all circumstances, while the reverse is 

 the case with those which are valuable; and this being equally true of 

 mental products, this mode of conveying an argument, independently of its 

 rhetorical advantages, has a logical value ; since it not only suggests the 

 grounds of the conclusion, but points to another case in which those grounds 

 have been found, or at least deemed to be, sufficient. 



On the other hand, when Bacon, who is equally conspicuous in the use 

 and abuse of figurative illustration, says that the stream of time has brought 

 down to us only the least valuable part of the writings of the ancients, as a 

 river carries froth and straws floating on its surface, while more weighty 

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

 onymous 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 semblance of argument in- 

 volved 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 resem- 

 blance of relations, an analogy in Ferguson's and Archbishop Whately's 

 sense: as in the preceding instance, in which an illustration from agricul- 

 ture was applied to mental cultivation. 



§ 8. To terminate the subject of Fallacies of Generalization, it remains 

 to be said, that the most fertile source of them is bad classification : bring- 

 ing together in one group, and under one name, things which have no com- 

 mon properties, or none but such as are too unimportant to allow general 

 propositions of any considerable value to be made respecting the class. 

 The misleading effect is greatest, when a word Avhich in common use ex- 

 presses some definite fact, is extended by slight links of connection 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 inceqtialiter d rebus abstracter, exemplifies 

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

 tiquity and of the Middle Ages. "Invenietur verbum istud, Humidum, 

 nihil ^liud quam nota confusa diversarum actionum, quae nuUam constanti- 

 am aut reductionem patiuntur. Significat enim, et quod circa aliud corpus 

 facile se circumf undit ; et quod in se est indeterminabile, nee consistere 

 potest ; et quod facile cedit undique ; et quod facile se dividit et dispergit ; 

 et quod facile se unit et colligit; et quod facile fluit, et in motu ponitur; 

 et quod alteri corpori facile adhsei'et, idque madefacit; et quod facile redu- 

 citur in liquidum, sive coUiquatur, cum antea consisteret. Itaque quum ad 

 hujus nominis prsedicationem et impositionem ventum sit ; si alia accipias, 

 flamma huraida est; si alia accipias, aer humidus non est; si alia, pulvis 

 minutus humidus est; si alia, vitrum humidum est: ut facile appareat, 



* Nov. Org., Aph. 60. 



