W. C. STEVE\Sf)\, (105-(75) 



force" in the sense of an entity, which arts as an effi- 

 cient cause of vital phenomena, is an assumption as 

 absurd as to assume that "electric," "attractive"' and 

 'chemical forces" are 'entities which determine the phe- 

 nomena of electricity, chemism and gravitation. 



" If we knew all the laws of the composition of matter, 

 and all the changes of which it iscapable, every phenom- 

 enon which any given substance presents, must be caused 

 either by something taking place in the substance, or 

 by something taking place out of it, but acting upon 

 if. Those mysterious forces, whether they be emana- 

 tions from matter, or whether they be merely properties 

 of matte]', must, in an ultimate analysis, depend either on 

 the internal arrangement or on the external locality 

 of their physical antecedents. However convenient, there- 

 fore, it may be in the present state of our knowledge, to 

 speak of vital principles, imponderable fluids and elastic 

 ethers, such terms can only be provisional and are to be 

 considered as mere names for that residue of unexplained 

 facts, which will be the business of future ages to bring 

 under generalizations wide enough to cover and include 

 the whole."' 



As mechanical energy manifests different powers and 

 results as it operates through differently constructed 

 mechanisms, so vital energy becomes more complex in its 

 manifestations as the organism, through which its work 

 is displayed, is more complicated in structure. 



Jevons has well defined the physiological significance 

 of vital force thus : " We are at freedom to imagine the 

 existence of a new agent, and to give it an appropriate 

 name, provided there are phenomena incapable of expla- 

 nation from known causes. We may speak of vital force 

 as occasioning life, provided that we do not take it to be 

 more than a name for an undefined something giving rise 

 to inexplicable facts, just as the French chemists called 

 Iodine the substance X, so long as they were unaware of 

 its real character and place in chemistry. Encke was 

 quite justified in speaking of the resisting medium in 

 space so long as the retardation of his comet could not 

 be otherwise accounted for." 



"But such hypotheses will do much harm whenever 

 they divert us from attemps to reconcile the facts with 



