THE CONSERVATION OF ENEKGY 131 



faith in matter and motion as the inmost substances 

 rather than the most abstract symbols of the sum 

 of existence." 



Are we then to argue, as some have done, that 

 the Law in question, whilst applicable to all in- 

 animate Nature is abrogated in the world of Life ? 



Here it is prudent to revert to the considerations 

 urged at the commencement of the chapter as to 

 the real nature and significance of the term " Law 

 of Nature," and to remember that this really means 

 a generalisation from the facts before us up to 

 date. " The term ' energy ' itself," says Sir Oliver 

 Lodge, 1 " as used in a definite sense by the physicist, 

 rather involves a modern idea, and is itself a 

 generalisation. Things as distinct from each other 

 as light, heat, sound, rotation, vibration, elastic 

 strain, gravitative separation, electric currents, and 

 chemical affinity, have all to be generalised under 

 the same heading (of the Conservation of Energy) 

 in order to make the law true. Until ' heat ' was 

 included in the list of energies, the statement could 

 not be made ; and a short time ago it was sometimes 

 discussed whether ' life ' should or should not be 

 included in the category of energy. I should give 

 the answer decidedly No, but some might be in- 

 clined to say Yes ; and this is sufficient as an 

 example to show that the categories of energy are 

 1 Life and Matter, p. 21. 



