DEMONSTRATION, AND NECESSARY TRUTHS. 161 



which at last, by the coutlnuation of tlie same progress, becomes an im- 

 possibility, of severing them from one another. If such be the pro- 

 gress of an experimental conviction of which the date is of yesterday, 

 and which is in opposition to first appearances, how must it fare with 

 those which are conformable to appearances femiliar from the first 

 dawn of intelligence, and of the coijclusiveness of which, from the 

 earliest records of human thought, no skeptic has suggested even a mo- 

 mentary doubt 1 



The other instance which we shall quote is a truly astonishing one. 

 and may be called the reductio ad ahsurdum of the theory of inconceiv- 

 ableness. Speaking of the laws of chemical composition, Mr. Wlie- 

 well says :* " That they could never have been clearly understood, and 

 therefore never firmly established, without laborious and exact exper- 

 iments, is certain ; but yet we may venture to say, that being once 

 kno\\'n, they possess an evidence beyond that of mere experiment. 

 For Jtoic, in fact, can tve conceive combinations, othenvise than as defi- 

 nite in kind and qicantity 1 If we were to suppose each element ready 

 to combine with any other indifferently, and indifferently in any quan- 

 tity, we should have a world in which all would be confusion and in- 

 definiteness. There would be no 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, capa- 

 ble of being classified and named, and of having general propositions 

 asserted concerning them. And as xoe cannot conceive a world in which 

 this should not he 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. Whewell's eminence should gravely as- 

 sert that we cannnot conceive a world in which the simple elements 

 would combine in other than definite proportions ; that by dint of med- 

 itating 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 in- 

 timate 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 contend- 

 ing, that one word more in illustration must be quite superfluous. I 

 shall, only, therefore, express my satisfaction that so long as the pro- 

 gi'ess of scientific instmction has not rendered this association as indis- 

 soluble in the minds of most people as Mr. Whewell finds it, the 

 majority of mankind will be fairly able to judge, from this example, of 

 the value of the evidence which he deems sufficient to prove that a 

 scientific proposition might be known to be true independently of 

 experience.! 



* Philosophy of the Indtictive Sciences, i., 384, 385. 



+ The Quarterly Review for June, 1841, contains an article, of great ability, on Mr. 

 Whewell's two great works, the writer of which maintains, on the subject of axioms, the 

 doctrine advanced in the text, that they are generalizations from experience, and supports 

 that opinion by a line of argument strikingly coinciding with mine. When I state that the 

 whole of the present chapter was written before I had seen the article (the greater part, 

 indeed, before it was published), it is not my object to occupy the reader's attention with a 

 matter so unimportant as the degree of oripinahty which may or may not belong to any 

 portion of my own speculations, but to obtain for an opinion which is opiiosed to reigning 

 doctrines, the recommendation derived from a striking concurrence of sentiment between 

 two inquirers entirely independent of one another. 1 have much pleasure in citing from a 

 writer of the extensive acquirements in physical and metaphysical knowledge and the ca- 



