VI PREFACE. 



and" structure of the brain. A strong line 

 of argument on this point has been put 

 forward by Dr. Bastian.* 



I have found it convenient to use the term 

 " mentation " for that physical action of the 

 brain which is associated with the phenomena 

 of mind ; as thus defined, mentation is a 

 function of the brain, physical in kind, and 

 capable of physical investigation. 



In the arguments here used it is postulated 

 as a working hypothesis, that all physical 

 phenomena are due to physical causes, or 

 necessarily follow upon certain physical ante- 

 cedents, and that every physical change is due 

 to a purely physical force. 



The methods here employed are those used 

 in physical research ; forces are studied in 

 the bodies or material objects where they 

 are seen, the physical expression of such 

 forces being noted as an index of the actual 

 but invisible. 



* " Brain as an Organ of the Mind " (International Science 

 Series), p. 188. 



