DEMONSTRATION, AND NECESSARY TRUTHS. 307 



in which there can be even a suspicion of an excep- 

 tion to the rule, that we should soon have a stronger 

 ground for believing the axiom, even as an experi- 

 mental truth, than we have for almost any of the 

 general truths which we confessedly learn from the 

 evidence of our senses. Independently of a priori 

 evidence, we should certainly believe it with an inten- 

 sity of conviction far greater than we accord to any 

 ordinary physical truth : and this too at a time of life 

 much earlier than that from which we date almost any 

 part of our acquired knowledge, and much too early 

 to admit of our retaining any recollection of the 

 history of our intellectual operations at that period. 

 Where then is the necessity for assuming that our recog- 

 nition of these truths has a different origin from the 

 rest of our knowledge, when its existence is perfectly 

 accounted for by supposing its origin to be the same ? 

 when the causes which produce belief in all other 

 instances, exist in this instance, and in a degree of 

 strength as much superior to what exists in other 

 cases, as the intensity of the belief itself is superior ? 

 The burden of proof lies upon the advocates of the 

 contrary opinion : it is for them to point out some 

 fact, inconsistent with the supposition that this part of 

 our knowledge of nature is derived from the same 

 sources as every other part. 



This, for instance, they would be able to do, if 

 they could prove chronologically that we have the 

 conviction (at least practically) so early in infancy as 

 to be anterior to those impressions on the senses, 

 upon which, on the other theory, the conviction is 

 founded. This, however, cannot be proved ; the point 

 being too far back to be within the reach of memory, 

 and too obscure for external observation. The advo- 

 cates of the a priori theory are obliged to have 



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