48 THEORETICAL BIOLOGY 



thereby brought into spatial activities, and this enormously 

 increased the difficulty of defining concept clearly. 



Only through the explanation that motion was the sole 

 cause of motion was the concept of force gradually eliminated 

 from physics. The word itself fell out of use, and in its place 

 was substituted the word energy, which merely indicates the 

 kind of motion. The movements of substances carried out in 

 space were described as kinetic energy ; by potential energy, 

 we understand motion stored up within substances. 



The law of the conservation of energy completed the 

 theoretical basis of physics, for it cleared the domain apper- 

 taining to that science of all that was extraneous, and taught 

 us to regard all material activities in space as isolated and 

 thus accessible to mathematical formularisation. 



Since the physico-chemical laws are, jointly and severally, 

 spatial in kind, it is only for practical reasons that I have 

 hitherto opposed them to the subjective laws of the domains 

 of sense : I certainly do not wish to ascribe to them any 

 higher reality, for that they do not possess. By referring 

 material processes to local signs and direction-signs, the sub- 

 jective nature even of these phenomena is demonstrated 

 beyond question, and the place of the so-called objective 

 natural sciences within biology becomes evident. 



Henceforth we are in a position to repudiate easily the 

 contention of the materialists or monists, which claims that 

 in the world there are only two realities — force and matter. 

 For if they are asked why local signs and direction-signs 

 should be more real than colours and sounds, they will cer- 

 tainly not be able to give any answer. Biology is quite able 

 to save the world from sinking to the low level to which 

 blind overestimation of physics is trying to reduce it. 



