DEMONSTRATION, AND NECESSARY TRUTHS. 273 



other ;" and he himself, though not venturing " absolutely 

 to pronounce" that all these laws " can be rigorously traced 

 to an absolute necessity in the nature of things,"* does actually 

 so think of the law just mentioned; of which he says: 

 " Though the discovery of the first law of motion was made, 

 historically speaking, by means of experiment, we have now 

 attained a point of view in which we see that it might have 

 been certainly known to be true, independently of experi- 

 ence.'^ Can there be a more striking exemplification than is 

 here afforded, of the effect of association which we have 

 described ? Philosophers, for generations, have the most 

 extraordinary difficulty in putting certain ideas together ; 

 they at last succeed in doing so ; and after a sufficient repeti- 

 tion of the process, they first fancy a natural bond between 

 the ideas, then experience a growing difficulty, which at last, 

 by the continuation of the same progress, becomes an impos- 

 sibility, of severing them from one another. If such be the 

 progress 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 appear- 

 ances familiar from the first dawn of intelligence, and of the 

 conclusiveness of which, from the earliest records of human 

 thought, no sceptic has suggested even a momentary doubt ? 



The other instance which I shall quote is a truly asto- 

 nishing one, and may be called the reductio ad absurdum of 

 the theory of inconceivableness. Speaking of the laws of 

 chemical composition, Dr. Whewell says :J " That they could 

 never have been clearly understood, and therefore never firmly 

 established, without laborious and exact experiments, is 

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

 known, they possess an evidence beyond that of mere experi- 

 ment. For how in fact can we conceive combinations, other- 

 wise than as definite in kind and quality ? If we were to 

 suppose each element ready to combine with any other indif- 

 ferently, and indifferently in any quantity, we should have a 



* Hist. Sc. Id., i. 263. t Ibid. 240. 



J Hist. Sc. Id., ii. 25, 26. 

 VOL. I. J 8 



