FALLACIES OF CONFUSION. 397 



bally what is required to support the conclusion, but not 

 really so. In the second great Fallacy of Confusion they are 

 neither verbally nor really sufficient, though, from their 

 multiplicity and confused arrangement, and still oftener 

 from defect of memory, they are not seen to be what they 

 are. The fallacy I mean is that of Petitio Principii, or 

 begging the question ; including the more complex and not 

 uncommon variety of it, which is termed Reasoning in a 

 Circle. 



Petitio Principii, as defined by Archbishop Whately, is the 

 fallacy &quot; in which the premise either appears manifestly to be 

 the same as the conclusion, or is actually proved from the 

 conclusion, or is such as would naturally and properly so be 

 proved.&quot; By the last clause I presume is meant, that it is 

 not susceptible of any other proof; for otherwise, there would 

 be no fallacy. To deduce from a proposition, propositions 

 from which it would itself more naturally be deduced, is often 

 an allowable deviation from the usual didactic order ; or at most, 

 what, by an adaptation of a phrase familiar to mathematicians, 

 may be called a logical inelegance.* 



The employment of a proposition to prove that on which 

 it is itself dependent for proof, by no means implies the degree 

 of mental imbecility which might at first be supposed. The 

 difficulty of comprehending how this fallacy could possibly be 

 committed, disappears when we reflect that all persons, even 

 the instructed, hold a great number of opinions without 

 exactly recollecting how they came by them. Believing that 

 they have at some former time verified them by sufficient 

 evidence, but having forgotten what the evidence was, they 

 may easily be betrayed into deducing from them the very pro 

 positions which are alone capable of serving as premises for 



* In his later editions, Archbishop Whately confines the name of Petitio 

 Principii &quot;to those cases in which one of the premises either is manifestly the 

 same in sense with the conclusion, or is actually proved from it, or is such as 

 the persons you are addressing are not likely to know, or to admit/except as an 

 inference from the conclusion : as, e.g. if any one should infer the authenticity 

 of a certain history, from its recording such and such facts, the reality of which 

 rests on the evidence of that history.&quot; 



