DEMONSTRATION, AND NECESSARY TRUTHS. 323 



fixed kinds of bodies ; salts, and stones, and ores, 

 would approach to and graduate into each other by 

 insensible degrees. Instead of this, we know that the 

 world consists of bodies distinguishable from each 

 other by definite differences, capable of being classi- 

 fied and named, and of having general propositions 

 asserted concerning them. And as we cannot conceive 

 a world in which this should not be the case, it would 

 appear that we cannot conceive a state of things in 

 which the laws of the combination of elements should 

 not be of that definite and measured kind which we 

 have above asserted." 



That a philosopher of Mr. WheweH's eminence 

 should gravely assert that we cannot concieve a world 

 in which the simple elements would combine in other 

 than definite proportions ; that by dint of meditating 

 on a scientific truth, the original discoverer of which 

 is still living, he should have rendered the association 

 in his own mind between the idea of combination and 

 that of constant proportions so familiar and intimate 

 as to be unable to conceive the one fact without the 

 other ; is so signal an instance of the law of human 

 nature for which I am contending, that one word 

 more in illustration must be quite superfluous. I 

 shall only, therefore, express my satisfaction that so 

 long as the progress of scientific instruction has not 

 rendered this association as indissoluble in the minds 

 of most people as Mr. Whewell finds it, the majo- 

 rity of mankind will be fairly able to judge, from this 

 example, of the value of the evidence which he deerns 

 sufficient to prove that a scientific proposition might 

 be known to be true independently of experience*. 



* The Quarterly Review for June, 1841, contains an article, of 

 great ability, on Mr. Whewell's two great works, the writer of 



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