OF MOTION AND REST.. S'J' 



are fictitious, and so our calculations are wholly 

 arbitrary, for in limitless Space all motion must be 

 relative : the bodies which from, certain points of 

 view seem to be at rest, from others seem to be in 

 motion, and so on alternately at rest and In motion 

 ad infinitum. Nor is there any theoretic reason to 

 be assigned for giving one point of view the pre- 

 ference over another.. If, then,. Motion is relative to 

 any and every point. It is relatiive to nothing, and! 

 does not admit of being objectively determined.. 

 And even If we were content that motion should be, 

 relative, yet energy must be real, and Indeed iits- 

 conservation Is one of the chief doctrines of modern 

 physics. But energy is ever generated out of and 

 passing into motion, and the amount of actual and 

 potential energy possessed by any system of bodies 

 would be relative to the points which for the purpose 

 of our calculations were feigned to be at rest. Thus 

 from one point of view a system might possess three 

 times the motive energy it has from another, and 

 the question arises which of these seeming energies 

 is the subject of the doctrine of the conservation of 

 energy. And in whatever way we answer, that 

 doctrine is false. For the points relatively to which 

 energy is conserved do not preserve their relative 

 positions for two moments together, and hence the 

 case to which the doctrine refers never arises. The 

 doctrine of the conservation of energy Is a purely 

 metaphysical assertion concerning a state of things 

 that cannot possibly arise in our experience. And 

 the same conviction of the entirely metempirlcal and 

 hypothetical character of the doctrine of the con- 

 servation of energy is forced upon us when we ex- 

 amine the statements which our physicists make 

 concerning it. For they admit that It does not 



