120 SCIENCE AND PSEUDO-SCIENCE m 



forms of energy, are mutually convertible; and, 

 therefore, that they all come under that general 

 law or statement of the order of facts, called 

 the conservation of energy. And, as that certainly 

 is an abstraction, so the view which the Duke of 

 Argyll thinks so extremely absurd is really one of 

 the commonplaces of physiology. But this Review 

 is hardly an appropriate place for giving instruction 

 in the elements of that science, and I content 

 myself with recommending the Duke of Argyll to 

 devote some study to Book II. chap. v. section 4 

 of my friend Dr. Foster's excellent text-book of 

 Physiology (1st edition, 1877, p. 321), which begins 

 thus : 



Broadly speaking, the animal body is a machine for converting 

 potential into actual energy. The potential energy is supplied 

 by the food ; this the metabolism of the body converts into the 

 actual energy of heat and mechanical labour. 



There is no more difficult problem in the world 

 than that of the relation of the state of conscious- 

 ness, termed volition, to the mechanical work 

 which frequently follows upon it. But no one can 

 even comprehend the nature of the problem, who 

 has not carefully studied the long series of modes 

 of motion which, without a break, connect the 

 energy which does that work with the general 

 store of energy. The ultimate form of the 

 problem is this : Have we any reason to believe 

 that a feeling, or state of consciousness, is capable 



