(j58 scepticism. 



%old good-of any actual system; iln any system of 

 bodies we. may choose to take, the sum of energy 

 does not remain the same from moment to moment. 

 What else is it then but to trifle with the .ignorance 

 of their hearers .to talk about demonstrating the 

 doctrine by actual experiment? They might as 

 well prove that two , parallel straight lines never 

 met by an assiduous use of the measuring tape. 

 And the case is no better, but rather worse, when it 

 is explained that strictly speaking the conservation 

 of energy holds only of an infinite system. For an 

 infinite system Is in the very nature of things im- 

 possible. It would be a whole which was not a 

 whole, a system which was not a system (Cf. ch. 9 

 § 8 and ch. 2 § 20). However it is put, the doctrine 

 can be asserted only of a fictitious case, well known 

 to be Impossible. 



And of the assumptions subsidiary to that of the 

 conservation of energy, the conception of potential 

 energy deserves special .criticism. For it illustrates 

 the haphazard way in which our science accepts 

 incompatible first principles. Potential energy Is 

 defined as energy of position. But how can there 

 be position in infinite Space? Position is deter- 

 mined with reference to at least three points, and 

 each of these with reference to three others, and so 

 on until we either get to fixed points with an ab- 

 solute position, or go on to infinity and are never 

 able to determine position at all. 



Thus the reality of Motion, Rest, Energy, and 

 Position In every case Involves metaphysical postul- 

 ates which experience does not satisfy, and we have] 

 agreed that for the present a reduction to meta- 

 physics shall be esteemed a reduction to absurdity. 



§ 9. The conception of Matter, which may next! 



