FALLACIES OF GENERALISATION. 



525 



ment for education, that if the soil is 

 left uncultivated, weeds will spring 

 up, the metaphor, though no proof, 

 but a statement of the thing to be 

 proved, 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 

 uncultivated 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 valu- 

 able ; and this being equally true of 

 mental products, this moide of convey- 

 ing 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 bot- 

 tom ; 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 sub- 

 stances float on a stream, and the 

 levity which is synonymous with 

 worthlessness, have nothing in com- 

 mon except the name ; and (to show 

 how little value there is in the meta- 

 phor) we need only change the word 

 into buoyancy, to turn the semblance 

 of argument involved in Bacon's illus- 

 tration against himself. 



A metaphor, then, is not to be con- 

 sidered 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 \evy remote from one 

 another ; the only resemblance exist- 

 ing 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 cultiva- 

 tion. 



§ 8. To terminate the subject of 

 Fallacies of Generalisation, it re- 

 mains to be said that the most fer- 

 tile source of them is bad classifica- 

 tion : 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 propositions of any con- 

 siderable value to be made respecting 

 the class. The misleading effect is 

 greatest when a word which in com- 

 mon use expresses some definite fact 

 is extended by slight links of connec- 

 tion 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 inaqualitei'- a rebus abstractce, exem- 

 plifies them by the notion of Humi- 

 dum or Wet, so familiar in the physics 

 of antiquity and of the Middle Ages. 

 " Invenietur verbum istud, Humidum 

 nihil aliud quam nota confusa diver- 

 sarum actionum, quae nullam con- 

 stantiam aut reductionem patiuntur. 

 Significat enim, et quod circa aliud 

 corpus facile se circumf undit ; et quod 

 in se est indeterminabiie, nee con- 

 sistere 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 adhseret, idque madefacit ; et 

 quod facile reducitur in liquidum, 

 sive colliquatur, cum antea consiste- 

 ret. Itaque quum ad hujus nominis 

 prsedicationem et impositionem ven- 

 tum sit ; si alia accipias, flamma 

 humida est ; si alia accipias, aer 

 humidus non est ; si alia, pulvis mi- 

 nutus huuiidus est ; si alia, vitrum 

 humidum est : ut facile appareat, 



* ^Yoi'. Org., Apb. 69. 



