510 FALLACIES. 



ably operates on most adventurers in lotteries; e.g., 'the gaining of a 

 high prize is no uncommon occurrence ; and what is no uncommon 

 occurrence may reasonably be expected ; tlierefore the gaining of a 

 high prize may reasonably be expected :' the conclusion when applied 

 to the individual (as in practice it is) must be understood in the sense 

 of ' reasonably expected hy a certain individual;^ therefore for the 

 major premiss to be true, the middle term must be understood to mean, 

 'no uncommon occurrence to some one particular ^Qx^on-^ whereas 

 for the minor (which has been placed first) to be true, you must 

 understand it of 'no uncommon occuiTence to some one or otlier ;^ 

 thus you will have the Fallacy of Composition." 



" This is a Fallacy with which men are extremely apt to deceive 

 ilieviselves ; for when a multitude of particulars are presented to the 

 mind, many are too weak or too indolent to take a comprehensive view 

 of them ; but confine their attention to each single point, by turns ; and 

 then decide, infer, and act accordingly : e. g., the imprudent spend- 

 thrift, finding that he is able to afford this, or that, or the other expense, 

 forgets that all of them together will ruin him." The debauchee de- 

 stroys his health by successive acts of intemperance, because no one of 

 those acts would be of itself sufficient to do him any serious harm. A sick 

 person reasons with himself, " one, and another, and another, of ray 

 symptoms, do not prove that I have a fatal disease ;" and practically 

 concludes that all taken together do not prove it. 



§ 2. We have now sufficiently exemplified one of the principal 

 Genera in this Order of Fallacies ; where, the source of error being 

 the ambiguity of terms, the premisses are verbally 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 that 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 

 " in which the premiss 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." 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 fi'om the usual didactic ordei' ; 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 upon which it is 

 itself dependent for proof, by no means implies the degree of mental 

 imbecihty which might at first be supposed. The difficulty of com- 

 prehending how this fallacy could possibly be committed, disappears 

 when we reflect that all persons, even philosophers, hold a great num- 

 ber of opinions without exactly recollecting how they came by them. 

 Believing that they have at some foiTner time veiified them by sufficient 

 evidence, but having forgotten what the evidence was, they may easily 

 be betrayed into deducing from them the very propositions which are 



