DEMONSTRATION, AND NECESSARY TRUTHS. 321 



the case, is no matter of conjecture. We know the 

 time, the persons, the circumstances, belonging to 

 each step of each discovery*." After such a testi- 

 mony, 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 for ever 

 to move in the same direction with undiminished 

 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 experience of the most familiar kind, which 

 taught that it was the nature of motion to abate 

 gradually, and at last terminate of itself. Yet when 

 once the contrary doctrine was firmly established, 

 mathematicians, as Mr. 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 Mr. Whewell, 

 though he has " not ventured absolutely to pro- 

 nounce" that all these laws " can be rigorously 

 traced to an absolute necessity in the nature of 

 thingst," does actually think in that manner of the 

 law just mentioned; of which he says: " Though the 

 discovery of the first law of motion was made, histo- 

 rically 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, inde- 



* Philosophy of the Inductive Sciences, i., 238. 

 f Ibid., 237. 

 VOL. I. Y 



