428 FALLACIES. 



moved out of its ordinary course by transient influ- 

 ences : which may equally be said of the mind. And 

 this susceptibility, whether of mind or body, must 

 arise from a weakness of the forces which maintain 

 and carry on the ordinary action of the system. All 

 this is conveyed in Mr. Carlyle's short sentence. And 

 since the causes are alike in the body and in the mind, 

 the analogy is a just one, and the maxim holds of the 

 one as much as of the other. 



Thus we see that the metaphor, although 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. The hearer 

 says, " Strength does not manifest itself in spasms, 

 very true ; and for what reason ?" Then in discover- 

 ing the reason, he finds it precisely as applicable to 

 the mind as it is to the body. This mode, therefore, 

 of conveying an argument, independently of its rhe- 

 torical advantages, has a logical value ; since it not 

 only suggests the grounds of the conclusion, but points 

 out 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 illus- 

 tration, 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 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 com- 

 mon except the name ; and (to show how little value 

 there is in the metaphor) we need only change the 



