238 THE WILL CANNOT CEEATE FORCE. 



hypothesis of " vital force or power " gives us 110 help, 

 for as we have seen, it is not a force, and he affirms it 

 is not an entity ; and, moreover, whether or not, it 

 cannot originate any force to express itself. For he 

 upholds the doctrine of the conservation of energy, and 

 denies that the said vital power can create force, and 

 declares that every expression of thought, including of 

 course reflex central stimulation, requires the death of 

 bioplasm and evolution of pre-existing energy. No 

 physicist, as far as I am aware, meets this except 

 J. Herschel, who plainly gives to the will of animals 

 the power of creating energy, although the quantity 

 may be very small each time. If so this is capable of 

 proof, for the food of an animal should yield more work 

 or heat when consumed by it, than when its potential 

 energy is used in any other way. No such proof has 

 been given, so no other physicist has admitted an ex- 

 ception to the law of conservation of energy, merely to 

 get over a physiological difficulty. However, although 

 no solution of the difficulty is yet offered by physiolo- 

 gists, yet we must remember we do not know why the 

 perception of one stimulus should be pleasing or the 

 reverse. That no doubt lies in the nature of the mole- 

 cular change set up by it, but of the nature of that 

 change nothing is known except by its effects, which, 

 however, are -equally perceptible in vital action un- 

 attended with consciousness. Therefore the cause of 

 avoidance of things causing disagreeable feelings may 

 lie in the vital action of which consciousness is the 

 passive perception, and thus no greater difficulty is 

 opposed to freedom of choice than is already given by 

 the non-existence of spontaneous action without 



