DEMONSTRATION AND l^ECESSARY TRUTHS. 



163 



selves ; the impossibility is in com- 

 bining them with facts inconsistent 

 with them, as part of the same mental 

 picture ; an obstacle of course only 

 felt by those who know the facts, and 

 are able to perceive the inconsistency. 

 As far as the suppositions themselves 

 are concerned, in the case of many of 

 Dr. Whewell's necessary truths the 

 negative of the axiom is, and probably 

 will be as long as the human race 

 lasts, as easily conceivable as the 

 affirmative. There is no axiom (for 

 example) to which Dr. Whewell as- 

 cribes a more thorough character of 

 necessity and self -evidence than that 

 of the indestructibility of matter. 

 That this is a true law of nature I 

 fully admit ; but I imagine there is 

 no human being to whom the opposite 

 supposition is inconceivable — who has 

 any difficulty in imagining a portion 

 of matter annihilated, inasmuch as 

 its apparent annihilation, in no respect 

 distinguishable from real by our un- 

 assisted senses, takes place every time 

 that water dries up, or fuel is con- 

 sumed. Again, the law that bodies 

 combine chemically in definite propor- 

 tions is undeniably true ; but few 

 besides Dr. Whewell have reached the 



Eoint which he seems personally to 

 ave arrived at, (though he only dares 

 prophesy similar success to the multi- 

 tude after the lapse of generations,) 

 that of being unable to conceive a 

 world in which the elements are ready 

 to combine with one another " indif- 

 ferently in any quantity ; " nor is it 

 likely that we shall ever rise to this 

 sublime height of inability, so long as 

 all the mechanical mixtures in our 

 planet, whether solid, liquid, or aeri- 

 form, exhibit to our daily observation 

 the very phenomenon declared to be 

 inconceivable. 



According to Dr. Whewell, these 

 and similar laws of nature cannot be 

 drawn from experience, inasmuch as 

 they are, on the contrary, assumed in 

 the interpretation of experience. Our 

 inability to "add to or diminish the 

 quantity of matter in the world," is 

 » truth which "neither i« nor can be 



derived from experience : for the ex- 

 periments 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."* True, it is as- 

 sumed ; but, I apprehend, no otherwise 

 than as all experimental inquiry as- 

 sumes provisionally some theory or 

 hypothesis, which is to be finally held 

 true or not, according as the experi- 

 ments decide. The hypothesis chosen 

 for this purpose will naturally be one 

 which groups together some consider- 

 able 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 appear- 

 ance 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 proceeded 

 to try whether, on more careful exa- 

 mination, the phenomena which ap- 

 parently pointed to a different con- 

 clusion 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 uni- 

 versal 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-evident 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 assumed, for the 

 purpose of connecting them by deduc- 



* J>Ml, ofJ)itc., pp. 472, 473. 



