66 Unconscious Memory- 



There can be no question as to the answer ; and hence 

 it comes that psychology is such an indispensable help to 

 physiology, whose fault it only in small part is that she 

 has hitherto made such little use of this assistance ; for 

 psychology has been late in beginning to till her fertile 

 field with the plough of the inductive method, and it is 

 only from ground so tilled that fruits can spring which can 

 be of service to physiology. 



If, then, the student of nervous physiology takes his 

 stand between the physicist and the psychologist, and if 

 the first of these rightly makes the unbroken causative 

 continuity of all material processes an axiom of his system 

 of investigation, the prudent psychologist, on the other 

 hand, will investigate the laws of conscious life according 

 to the inductive method, and will hence, as much as the 

 physicist, make the existence of fixed laws his initial 

 assumption. If, again, the most superficial introspection 

 teaches the physiologist that his conscious life is dependent 

 upon the mechanical adjustments of his body, and that 

 inversely his body is subjected with certain limitations 

 to his will, then it only remains for him to make one 

 assumption more, namely, that this mutual interdefendence 

 between the spiritual and the material is itself also dependent 

 on law, and he has discovered the bond by which the 

 science of matter and the science of consciousness are 

 united into a single whole. 



Thus regarded, the phenomena of consciousness become 

 functions of the material changes of organised substance, 

 and inversely — though this is involved in the use of the 

 word " function " — the material processes of brain sub- 

 stance become functions of the phenomena of consciousness. 

 For when two variables are so dependent upon one another 

 in the changes they undergo in accordance with fixed laws 

 that a change in either involves simultaneous and corre- 

 sponding change in the other, the one is called a function 

 of the other. 



This, then, by no means implies that the two variables 



