596 THE POPULAR SCIENCE MONTHLY. 



which might equally well or better be called the theory of the 

 metamorphosis of motions, is indispensable to the doctrine of evo- 

 lution. But for the theory that light, heat, electricity, and nerve- 

 action are different modes of undulatory motion transformable 

 one into another, and that similar modes of motion are liberated 

 by the chemical processes going on within the animal or vegetal 

 organism, Mr. Spencer's work could never have been done. That 

 theory of correlation and transformation is now generally ac- 

 cepted, and is often appealed to by materialists. A century ago 

 Cabanis said that the brain secretes thought as the liver secretes 

 bile. If he were alive to-day, he would doubtless smile at this old 

 form of expression as crude, and would adopt a more subtle 

 phrase ; he would say that " thought is transformed motion." 



Against this interpretation I have maintained that the theory 

 of correlation not only fails to support it, but actually overthrows 

 it. The arguments may be found in the chapter on Matter and 

 Spirit in my Cosmic Philosophy, published in 1874, and in the 

 essay entitled A Crumb for the Modern Symposium, written in 

 1877 and reprinted in Darwinism and other Essays.* Their pur- 

 port is, that in tracing the correlation of motions into the organism 

 through the nervous system, and out again, we are bound to get 

 an account of each step in terms of motion. Unless we can show 

 that every unit of motion that disappears is transformed into an 

 exact quantitative equivalent, our theory of correlation breaks 

 down ; but when we have shown this we shall have given a com- 

 plete account of the whole affair without taking any heed what- 

 ever of thought, feeling, or consciousness. In other words, these 

 psychical activities do not enter into the circuit, but stand outside 

 of it, as a segment of a circle may stand outside a portion of an 

 entire circumference with which it is concentric. Motion is 

 never transformed into thought, but only into some other form 

 of measurable (in fact, or, at any rate, in theory measurable) 

 motion that takes place in nerve-threads and ganglia. It is not 

 the thought, but the nerve-action that accompanies the thought, that 

 is really "transformed motion." I say that, if we are going to 

 verify the theory of correlation, it must be done (actually or 

 theoretically) by measurement ; quantitative equivalence must be 

 proved at every step ; and hence we must not change our unit of 

 measurement ; from first to last it must be a unit of' motion : if 

 we change it for a moment, our theory of correlation that moment 

 collapses. I say, therefore, that the theory of correlation and 

 equivalence of forces lends no support whatever to materialism. 

 On the contrary, its manifest implication is that psychical life 

 can not be a mere product of temporary collocations of matter. 



* See also Excursions of an Evolutionist, pp. 274-282. 



