510 POPULAR SCIENCE MONTHLY. 



explain tlie phenomena by reference to psychological principles 

 only. Or, finally, we may adopt the time-honored doctrine which 

 regards mind and brain as two distinct entities, between which 

 constant interaction is going on. We may then invoke both 

 principles in our theories. 



The first of these doctrines is commonly known as materialism, 

 but as that word has been so much abused I shall use the phrase 

 " theory of dependence." It has its root in the obvious fact that 

 sensations and emotions are caused by physical and physiological 

 processes. Recent physiological research has tended to establish 

 this doctrine more firmly, to extend its scope and to determine 

 the character of the relation. There is much evidence to show 

 that thought, reason, and will are also dependent upon the brain 

 for their very existence; that all mental states are especially 

 connected with the cortex of the brain; that even some very 

 complicated movements, to the performance of which we usually 

 suppose consciousness to be essential, can be performed by lower, 

 presumably unconscious, centers. All this tends to exalt our idea 

 of the brain's capacities and to diminish the importance ascribed 

 to mind. Moreover, careful psychological work has shown that 

 many of what are termed mental laws are most easily explained 

 as representing physical processes, and the sharp antithesis which 

 we draw between the laws of mind and those of matter is in part 

 at least illusory. The law of association is believed to be capable 

 of interpretation in terms of the transmission of nervous im- 

 pulses through the cortex, the laws of volition in their simpler 

 forms point to a direct discharge of energy developed in connec- 

 tion with some substantive mental state into the subcortical 

 mechanism and thence to the muscles, the law of attention sug- 

 gests some species of coalescence of all the activities going on at 

 one time in the cortex into a definite system. Even telepathy, 

 which is regarded with so much suspicion by orthodox jjsycholo- 

 gists, is parallel to the phenomena of induction. 



The more special lines of work, therefore, both in physiology 

 and psychology, tend to converge upon the same conclusion to 

 which we are already predisposed by the general drift of the 

 intellectual movement initiated by Gasseudi, Hobbes, Descartes, 

 Galileo, and Newton that it is to matter we must look for our 

 knowledge of Nature, that material processes are independent 

 and self-sufficient, that mind is merely a brain product, which 

 waxes and wanes with the flow and ebb of physical activities 

 within the cortex. 



The attempts that have been made to explain some or all of 

 the phenomena of suggestibility and automatism by reference to 

 physical changes are almost innumerable, and scarcely any con- 

 ceivable attribute of the brain or its functions has not been 



