VII. On the Nature of the Truth of the Laws of Motion. By the 

 Rev. W. Whewell, M.A. Fellow and Tutor of Trinity College. 



[Bead Feb. 17, 1834.] 



1. The long continuance of the disputes and oppositions of opinion 

 which have occurred among theoretical writers concerning the elementary 

 principles of Mechanics, may have made such discussions appear to some 

 persons wearisome and unprofitable. I might, however, not unreasonably 

 plead this very circumstance as an apology for offering a new view of 

 the subject; since the extent to which these discussions have already 

 gone shews that some men at least take a great interest in them ; 

 and it may be stated, I think, without fear of contradiction, that 

 these controversies have not terminated in the general and undisputed 

 establishment of any one of the antagonist opinions. 



The question to which my remarks at present refer is this: "What 

 is the kind and degree of cogency of the best proofs of the laws of 

 motion, or of the fundamental principles of mechanics, exprest in any 

 other way?" Are these laws, philosophically considered, necessary, and 

 capable of demonstration by means of self-evident axioms, like the 

 truths of geometry ; or are they empirical, and only known to be true 

 by trial and observation, like such general rules as we obtain in natural 

 history ? 



It certainly appears, at first sight, very difficult to answer the argu- 

 ments for either side of this alternative. On the one hand it is said, 

 the laws of motion cannot be necessarily true, for if they were so, the 

 denial of them would involve a contradiction. But this it does not, 

 for we can readily conceive them to be other than they are. We can 

 conceive that a body in motion should have a natural tendency to 

 move slower and slower. And we know that, historically speaking, 

 Vol. V. Paet II. U 



