460 FALLACIES. 



mutual coherency for truth ; to trust one's safety 

 to a strong chain although it has no point of support ; 

 is at the bottom of much which, when reduced to the 

 strict forms of argumentation, can exhibit itself no 

 otherwise than as reasoning in a circle. All experi- 

 ence bears testimony to the enthralling effect of neat 

 concatenation in a system of doctrines, and the diffi- 

 culty with which men admit the persuasion that any- 

 thing which holds so well together can possibly fall. 



Since every case where a conclusion which can 

 only be proved from certain premisses is used for the 

 proof of those premisses, is a case of petitio principii, 

 that fallacy includes a very great proportion of all 

 incorrect reasoning. It is necessary, for completing 

 our view of the fallacy, to exemplify some of the dis- 

 guises under which it is accustomed to mask itself, 

 and to escape exposure. 



A proposition would not be admitted by any per- 

 son in his senses as a corollary from itself, unless it 

 were expressed in language which made it seem dif- 

 ferent. One of the commonest modes of so expressing 

 it, is to present the proposition itself, in abstract terms, 

 as a proof of the same proposition expressed in con- 

 crete language. This is a very frequent mode not 

 only of pretended proof, but of pretended explana- 

 tion ; and is parodied by Moliere when he makes one 

 of his absurd physicians say, " Topium endormit 

 parcequ'il a une vertu soporifique," or, in the amusing 

 doggrel quoted by Mr. Whewell, 



Mihi demandatur 



A doctissimo doctore, 

 Quare opium facit dormire; 



Et ego respondeo, 



Quia est in eo 



Virtus dormitiva, 

 Cujus natura est sensus assoupirc. 



