538 



FALLACIES. 



Arguing in a circle, however, is a 

 stronger case of the fallacy, and im- 

 plies more than the mere passive re- 

 ception of a premise by one who does 

 not remember how it is to be proved. 

 It implies an actual attempt to prove 

 two propositions reciprocally from one 

 another ; and is seldom resorted to, 

 at least in express terms, by any per- 

 son in his own speculations, but is 

 committed by those who, being hard 

 pressed by an adversary, are forced 

 into giving reasons for an opinion of 

 which, when they began to argue, they 

 had not sufficiently considered the 

 grounds. As in the following example 

 from Archbishop Whately : * ' Some 

 mechanicians attempt to prove (what 

 they ought to lay down as a probable 

 but doubtful hypothesis *) that every 

 particle of matter gravitates equally : 

 'why?' 'because those bodies which 

 contain more particles ever gravitate 

 more strongly, i.e. are heavier : ' * but, 

 (it may be urged,) those which are 

 heaviest are not always more bulky ; * 

 ' no, but they contain more particles, 

 though more closely condensed :' 'how 

 do you know that?' ' because they are 

 heavier : ' ' how does that prove it ? ' 

 • because all particles of matter gravi- 

 tating equally, that mass which is 

 specifically the heavier must needs 

 have the more of them in the same 

 space.' " It appears to me that the 

 fallacious reasoner, in his private 

 thoughts, would not be likely to pro- 

 ceed beyond the first step. He would 

 acquiesce in the sufficiency of the rea- 

 son first given, " bodies which contain 

 more particles are heavier." It is 

 when he finds this questioned, and is 

 called upon to prove it, without know- 

 ing how, that he tries to establish his 

 premise by supposing proved what he 

 is attempting to prove by it. The 

 most effectual way, in fact, of expos- 

 ing a Petitio Principii, when circum- 

 stances allow of it, is by challenging 



* No longer even a probable hyrothesis, 

 oince the establishment of the atomic the- 

 ory ; it l)eiiig now cei tuin that the integral 

 particles of different substances gravitate 

 uueijually. It is true that these particles, 



the reasoner to prove his premises ; 

 which if he attempts to do, he is 

 necessarily driven into arguing in a 

 circle. 



It is not uncommon, however, for 

 thinkers, and those not of the lowest 

 description, to be led even in their 

 own thoughts, not indeed into for- 

 mally proving each of two propo- 

 sitions from the other, but into ad- 

 mitting propositions which can only 

 be so proved. In the preceding ex- 

 ample the two together form a com- 

 plete and consistent, though hypothe- 

 tical, explanation of the facts con- 

 cerned. And the tendency to mistake 

 mutual coherency for truth, to trust 

 one's safety to a strong chain though 

 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 experience 

 bears testimony to the enthralling 

 effect of neat concatenation in a sys- 

 tem of doctrines, and the difficulty 

 with which people admit the persua- 

 sion that anything which holds so 

 well together can possibly fall. 



Since every case where a conclusion 

 which can only be proved from cer- 

 tain premises is used for the proof of 

 those premises is a case of petitio 

 principii, that fallacy includes a very 

 great proportion of all incorrect rea- 

 soning. It is necessary, for complet- 

 ing our view of the fallacy, to ex- 

 emplify some of the disguises under 

 which it is accustomed to mask itself, 

 and to escape exposure. 



A proposition would not be ad- 

 mitted by any person in his senses 

 as a corollary from itself, unless it 

 were expressed in language which 

 made it seem different. 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 concrete lan- 



thongh real minima for the purposes of '. 

 CI emical combination, may not be the ulti- 

 mate particles of the su Instance ; and this 

 doTibt alone renders the hypothesis admis- 

 sible, even as au hypothesis. 



