FALLACIES OF CONFUSION. 403 



third book, being, that if the wise oould be unhappy, there 

 was little use in pursuing wisdom. But by unhappiness they 

 did not mean pain or suffering ; to that, it was granted that 

 the wisest person was liable in common with others : he was 

 happy, because in possessing wisdom he had the most valu- 

 able of all possessions, the most to be sought and prized of all 

 things, and to possess the most valuable thing was to be the 

 most happy. By laying it down, therefore, at the commence- 

 ment of the inquiry, that the sage must be happy, the dis- 

 puted question respecting the summum bonum was in fact 

 begged ; with the further assumption, that pain and suffering, 

 so far as they can coexist with wisdom, are not unhappiness, 

 and are no evil. 



The following are additional instances of Petitio Principii, 

 under more or less of disguise. 



Plato, in the Sophistes, attempts to prove that things may 

 exist which are incorporeal, by the argument that justice and 

 wisdom are incorporeal, and justice and wisdom must be 

 something. Here, if by something be meant, as Plato did in 

 fact mean, a thing capable of existing in and by itself, and 

 not as a quality of some other thing, he begs the question in 

 asserting that justice and wisdom must be something : if he 

 means anything else, his conclusion is not proved. This 

 fallacy might also be classed under ambiguous middleterm : 

 something, in the one premise, meaning some substance, in 

 the other merely some object of thought, whether substance 

 or attribute. 



It was formerly an argument employed in proof of what 

 is now no longer a popular doctrine, the infinite divisibility of 

 matter, that every portion of matter, however small, must at 

 least have an upper and an under surface. Those who used 

 this argument did not see that it assumed the very point in 

 dispute, the impossibility of arriving at a minimum of thick- 

 ness ; for if there be a minimum, its upper and under surface 

 will of course be one : it will be itself a surface, and no more. 

 The argument owes its very considerable plausibility to this, 

 that the premise does actually seem more obvious than the 

 conclusion, though really identical with it. As expressed in 



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