l6o 



REASONING. 



experience, because their falsity is in- 

 conceivable. But Dr. WheweU him- 

 self says that we are continually led, 

 by the natural progress of thought, 

 to regard as inconceivable what our 

 forefathers not only conceived but 

 believed, nay even (he might have 

 added) were unable to conceive the 

 reverse of. He cannot intend to justify 

 this mode of thought : he cannot mean 

 to say that we can be right in re- 

 garding as inconceivable what others 

 have conceived, and as self-evident 

 what to others did not appear evident 

 at all. After so complete an admis- 

 sion that inconceivableness is an 

 accidental thing, not inherent in the 

 phenomenon itself, but dependent on 

 the mental history of the person who 

 tries to conceive it, how can he ever 

 call upon us to reject a proposition as 

 impossible on no other ground than 

 its inconceivableness? Yet he not 

 only does so, but has unintentionally 

 afforded some of the most remarkable 

 examples which can be cited of the very 

 illusion which he has himself so clearly 

 pointed out. I select as specimens his 

 remarks on the evidence of the three 

 laws of motion, and of the atomic 

 theory. 



With respect to the laws of motion, 

 Dr. Whewell says : " No one can 

 doubt that, in historical fact, these 

 laws were collected from experience. 

 That such is the case is no matter of 

 conjecture. We know the time, the 

 persons, the circumstances, belonging 

 toeach step of each discovery."* After 

 this testimony, to adduce evidence of 

 the fact would be superfluous. And 

 not only were these laws by no means 

 intuitively evident, but some of them 

 were originally paradoxes. The first 

 law was especially so. That a body, 

 once in motion, would continue forever 

 to move in the same direction with un- 

 diminished velocity unless acted upon 

 by some new force, was a proposition 

 which mankind found for a long time 

 the greatest difficulty in crediting. 

 It stood opposed to apparent experi- 



• Hiitoi-y of Scientific Ideas, i. 264. 



ence of the most familiar kind, which 

 taught that it was the nature of mo- 

 tion to abate gradually, and at last 

 terminate of itself. Yet when once 

 the contrary doctrine was firmly es- 

 stablished, mathematicians, as Dr. 

 Whewell observes, speedily began to 

 believe that laws, thus contradictory 

 to first appearances, and which, even 

 after full proof had been obtained, it 

 had required generations to render 

 familiar to the minds of the scientific 

 world, were under a " demonstrable 

 necessity, compelling them to be such 

 as they are and no other ; " and he 

 himself, though not venturing "abso- 

 lutely to pronounce" that aU 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, histori- 

 cally speaking, by means of experi- 

 ment, we have now attained a point 

 of view in which we see that it might 

 have been certainly known to be true 

 independently of experience." f Can 

 there be a more striking exemplifica- 

 tion than is here afforded of the effect 

 of association which we have described ? 

 Philosophers, for generations, have the 

 most extraordinary difficulty in put- 

 ting certain ideas together ; they at 

 last succeed in doing so ; and after a 

 sufificient repetition of the process, 

 they first fancy a natural bond be- 

 tween the ideas, then experience a 

 growing difficulty, which at last, by 

 the continuation of the same progress, 

 becomes an impossibility, of severing 

 them from one another. If such be 

 the progress of an experimental con- 

 viction of which the date is of yester- 

 day, 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 sug- 

 gested even a momentary doubt ? 



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



