THE INDIRECT JUSTIFICATION OF ENTELECHY 159 



regard to its surroundings has remained unaltered in amount 

 in spite of all internal changes. The system's state at t 

 as a whole has been the " cause " of its state at 2 ; but as 

 a causal system with regard to its surroundings it has 

 remained the same. 



Let us now study two systems in the sense described, 

 and let us assume that there are causal processes going on 

 between these two systems, but in no other way or direction. 

 Then we call the whole of the change of the totality of the 

 one the cause of the whole of the change of the other, 

 and are convinced that both changes are equal in amount. 



It is upon these two fictions that the principle of the 

 conservation of energy rests, and from these two fictions it 

 derives its two fundamental modern formulations : " the 

 energy of an isolated l system is constant," and, " any loss 

 of energy in one isolated system corresponds to an equivalent 

 gain in another one," and vice versa. Robert Mayer was 

 well aware that his principle was based upon an aprioristic 

 foundation, and he did well to place in the beginning of his 

 discussion the two phrases : " causa aequat effectum " and 

 " nihil fit ex nihilo aut ad nihilum." In fact, it is upon 

 a combination of the categories of causality and of quantity 

 that the aprioristic part of the principle of the conservation 

 of energy rests : energy is causality quantitatively determined. 



1 It is meaningless to speak of the energetic constancy of the universe, as 

 long as the problem of its material fmiteness or infiniteness is unsolved. In 

 the case of its infiniteness, of course, to speak of " constancy " would be 

 altogether meaningless. 



2 An important but secondary formulation of the principle in question is 

 the following : the amount of energy of an isolated system is univocally 

 determined in every movement, and the total causal effect due to such a 

 system the "work" done by it if its "energy" is reduced to zero, is 

 independent of the way of transformation. 



