170 Mr WHEWELL, ON THE NATURE OF THE TRUTH 



This being understood, it will be observed that the part of each law 

 which is here stated as empirical, consists, in each case, of a negation 

 of the supposition that the condition of the moving body with respect 

 to motion and action, is a cause of any change in the circumstances of 

 its motion; and from this it follows that these circumstances are de- 

 termined entirely by the forces extraneous to the body itself. 



23. This mode of considering the question shews us in what 

 manner the laws of motion may be said to be proved by their sim- 

 plicity, which is sometimes urged as a proof. They undoubtedly have 

 this distinction of the greatest possible simplicity, for they consist in 

 the negation of all causes of change, except those which are essential 

 to our conception of such causation. We may conceive the motions 

 of bodies, and the effect of forces upon them, to be regulated by the 

 lapse of time, by the motion which the bodies have, by the forces 

 previously acting ; but though we may imagine this as possible, we do 

 not find that it is so in reality. If it were, we should have to con- 

 sider the effect of these conditions of the body acted on, and to com- 

 bine this effect with that of the acting forces ; and thus the motion 

 would be determined by more numerous conditions and more complex 

 rules than those which are found to be the laws of nature. The laws 

 which, in reality, govern motion are the fewest and simplest possible, 

 because all are excluded, except those which the very nature of laws 

 of motion necessarily implies. The prerogative of simplicity is possessed 

 by the actual laws of the universe, in the highest perfection which is 

 imaginable or possible. Instead of having to take into account all the 

 circumstances of the moving bodies, we find that we have only to 

 reject all these circumstances. Instead of having to combine empirical 

 with necessary laws, we learn empirically that the necessary laws are 

 entirely sufficient. 



24. Since all that we learn from experience is, that she has no- 

 thing to teach us concerning the laws of motion, it is very natural 

 that some persons shovdd imagine that experience is not necessary to 

 their proof. And accordingly many writers have undertaken to esta- 

 blish all the fundamental principles of mechanics by reasoning alone. 



