136 SCIENCE AND MORALS. iii 



pain. Now, if I trace these last nerve-filaments, 

 I find them to be ultimately connected with part 

 of the substance of the brain, just as the others 

 turn out to be connected with muscular sub- 

 stance. If the production of motion in the one 

 case is properly said to be the function of the 

 muscular substance, why is the production of a 

 state of consciousness in the other case not to be 

 called a function of the cerebral substance? Once 

 upon a time, it is true, it was supposed that a 

 certain " animal spirit " resided in muscle and 

 was the real active agent. But we have done 

 with that wholly superfluous fiction so far as the 

 muscular organs are concerned. Why are we to 

 retain a corresponding fiction for the nervous 

 organs? 



If it is replied that no physiologist, however 

 spiritual his leanings, dreams of supposing that 

 simple sensations require a " spirit " for their pro- 

 duction, then I must point out that we are all 

 agreed that consciousness is a function of mat- 

 ter, and that particular tenet must be given up 

 as a mark of Materialism. Any further argu- 

 ment will turn upon the question, not whether 

 consciousness is a function of the brain, but 

 whether all forms of consciousness are so. Again, 

 I hold it would be quite correct to say that ma- 

 terial changes are the causes of psychical phe- 

 nomena (and, as a consequence, that the organs 

 in which these changes take place have the pro- 



