278 REASONING. 



the contrary, assumed in the interpretation of experience. Our 

 inability to &quot; add to or diminish the quantity of matter in the 

 world,&quot; is a truth which &quot; neither is nor can be derived from, 

 experience ; for the experiments which we make to verify it 

 presuppose its truth. . . . When men began to use the 

 balance in chemical analysis, they did not prove by trial, but 

 took for granted, as self-evident, that the weight of the whole 

 must be found in the aggregate weight of the elements.&quot;* 

 True, it is assumed ; but, I apprehend, no otherwise than as 

 all experimental inquiry assumes provisionally some theory or 

 hypothesis, which is to be finally held true or not, according as 

 the experiments decide. The hypothesis chosen for this pur 

 pose will naturally be one which groups together some consi 

 derable number of facts already known. The proposition that 

 the material of the world, as estimated by weight, is neither 

 increased nor diminished by any of the processes of nature or 

 art, had many appearances in its favour to begin with. It 

 expressed truly a great number of familiar facts. There were 

 other facts which it had the appearance of conflicting with, 

 and which made its truth, as an universal law of nature, at first 

 doubtful. Because it was doubtful, experiments were devised 

 to verify it. Men assumed its truth hypothetically, and pro 

 ceeded to try whether, on more careful examination, the pheno 

 mena which apparently pointed to a different conclusion, would 

 not be found to be consistent with it. This turned out to be 

 the case ; and from that time the doctrine took its place as an 

 universal truth, but as one proved to be such by experience. 



! That the theory itself preceded the proof of its truth that it 

 had to be conceived before it could be proved, and in order 

 /? that it might be proved does not imply that it was self-evi 

 dent, and did not need proof. Otherwise all the true theories 



\ in the sciences are necessary and self-evident; for no one 

 knows better than Dr. Whewell that they all began by being 



ti assumed, for the purpose of connecting them by deductions 



I with those facts of experience on which, as evidence, they now 



/ confessedly rest.t 



\J * Phil, of Disc., pp. 472, 473. 



t The Quarterly Review for June 1841, contained an article of great ability 



