AND ITS SELF-CONSERVATION. 149 



The latter found the expression, "conservation of force/' 

 objectionable because it "implies a conserver and an act 

 of conservation ; " which would seem to mean that the 

 expression implies that force is conserved by an agency 

 apart from force. Accordingly, at Professor Huxley's 

 suggestion, Mr. Spencer * substituted the expression, 

 " persistence of force," for ' ' conservation of force. " 



But the persistence of force (or energy, as we are now- 

 to say) surely implies that the ultimate unit is self -active ; 

 that its very persistence is a manifestation of spontaneity. 

 In other words, the expression, "persistence of energy/' 

 is preferable to the expression, "conservation of energy/' 

 only because it brings very near to the surface the concep- 

 tion that the process of the conservation of energy involves 

 the immeasurably significant characteristic of ^//'-con- 

 servation. It is thus, and thus alone, that it does or can 

 "persist." 



It is this view of a self-active, self-conserved energy 

 that opens the way to an adequate explanation of motion. 

 And now, having obtained a first assured view of a prin- 

 ciple adequate to explain to the reason what to the senses 

 is the unquestionable fact of motion, let us return to the 

 question of the accepted law of universal gravitation. 



* See note to heading of Chapter VI. of "First Principles.'' 1 



