SCIENCE AND PSEUDO-SCIENCE. 221 



The Duke of Argyll may not be aware of the fact, but it is never- 

 theless true, that when a man's arm is raised, in sequence to that state 

 of consciousness we call a volition, the volition is not the immediate 

 cause of the elevation of the arm. On the contrary, that operation is 

 effected by a certain change of form, technically known as " contrac- 

 tion " in sundry masses of flesh, technically known as muscles, which 

 are fixed to the bones of the shoulder in such a manner that, if these 

 muscles contract, they must raise the arm. Now, each of these mus- 

 cles is a machine, in a certain sense, comparable to one of the donkey- 

 engines of a steamship, but more complete, inasmuch as the source of 

 its ability to change its form, or contract, lies within itself. Every 

 time that, by contracting, the muscle does work, such as that involved 

 in raising the arm, more or less of the material which it contains is 

 used up, just as more or less of the fuel of a steam-engine is used up, 

 when it does work. And I do not think there is a doubt in the mind 

 of any competent physicist or physiologist that the work done in lifting 

 the weight of the arm is the mechanical equivalent of a certain propor- 

 tion of the energy set free by the molecular changes which take place 

 in the muscle. It is further a tolerably well-based belief that this, and 

 all other 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, Chapter V, section 

 4, of my friend Dr. Fosters excellent " Text-Book of Physiology " (first 

 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 metabo- 

 lism of the body converts into the actual energy of heat and mechanical labor. 



There is no more difficult problem in the world than that of the 

 relation of the state of consciousness, termed volition, to the mechani- 

 cal work which frequently follows upon it. But no one can even com- 

 prehend 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 of directly affect- 

 ing the motion of even the smallest conceivable molecule of matter ? 

 Is such a thing even conceivable ? If we answer these questions in 

 the negative, it follows that volition may be a sign, but can not be a 

 cause of bodily motion. If we answer them in the affirmative, then 

 states of consciousness become undistinguishable from material things ; 



