FALLACIES OF SIMPLE INSPECTION. 355 



religious character, probably in part also arose from 

 the prejudice that a wonderful thing must of course 

 have wonderful properties. 



$ 3. The instances of a priori fallacy which we ha,ve 

 hitherto cited, belong to the class of vulgar errors, and 

 do not now, nor in any but a rude age ever could, 

 impose upon minds of any considerable attainments. 

 But those to which we are about to proceed, have 

 been, and still are, all but universally prevalent even 

 among philosophers. The same disposition to give 

 objectivity to a law of the mind to suppose that 

 what is true of our ideas of things must be true of the 

 things themselves exhibits itself in many of the most 

 accredited modes of philosophical investigation, both 

 on physical and on metaphysical subjects. In one of 

 its most undisguised manifestations, it embodies itself 

 in two maxims, which lay claim to axiomatic truth: 

 Things which we cannot think of together, cannot 

 coexist ; and, Things which we cannot help thinking 

 of together, must coexist. I am not sure that the 

 maxims were ever expressed in these precise words, 

 but the history both of philosophy and of popular 

 opinions abounds with exemplifications of both forms 

 of the doctrine. 



To begin with the latter of them : Things which we 

 cannot think of except together, must exist together. 

 This is assumed in the many reasonings of philosophers 

 which conclude that A must accompany B in point 

 of fact, because "it is involved in the idea." Such 

 thinkers do not reflect that the idea, being a result of ab- 

 straction, ought to conform to the facts, and cannot make 

 the facts conform to it. The argument is at most admis- 

 sible as an appeal to authority; a surmise, that what is 

 now part of the idea must, before it became so, have been 



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