en. XVII.] SOCIOLOGY AND FREE-WILL. 177 



action wliicii is attended by a conscious comparison of im- 

 pressions, and which involves nutritive changes in the cere- 

 brum or cerebellum, or in both. As we saw in the pre- 

 ceding chapter, the sequence of actions upon impressions is 

 either reflex or instinctive, and in either case automatic, so 

 long as the nervous energy liberated by the impression is 

 instantly disclmrged through a completely permeable chan- 

 nel or set of channels. But in those higher organisms in 

 which an immensely varied experience has established innu- 

 merable complex systems of less permeable channels, there 

 intervenes between the liberation of energy in the brain and 

 its discharge upon the motor centres a period during which 

 there is a tension between various nerve- currents, each seek- 

 ing to discharge itself along the most permeable lines of 

 transit. We saw also that this period of tension is a period 

 of conscious deliberation, involving conscious reflection, and 

 feelings of desire or aversion. And these views turned out 

 to be justified by the fact that as soon as the frequent repeti- 

 tion of any given set of experiences has rendered all the 

 transit-lines involved in the case completely permeable, so 

 that there is no longer any appreciable period of tension, 

 then the acts once conscious and voluntary become invo- 

 luntary and automatic. 



Now the state of consciousness called Desire is accom- 

 panied by a nascent excitement of the nerve-fibres distributed 

 upon the muscular apparatus whose activity is requisite for 

 the attainment of the desired object. There is a tendency to 

 go through with the movements needful for realizing the 

 desire ; and this tendency, unless neutralized by an an- 

 tagonist tendency, must end in action. In the language of 

 dynamics, tension when not counteracted by opposing 

 tension, must pass into vis viva. This passage of nervous 

 lenrfion into nervous vu viva couytitutes volUion, which may 



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