MIND IS FUNCTION 159 



says, "Surely no one, who is cognizant of the facts of 

 the case, nowadays doubts that the roots of psychology 

 lie in the physiology of the nervous system. What we 

 call the operations of the mind are the functions of the 

 brain, and the materials of consciousness are products 

 of cerebral activity." The strict line of demarcation 

 between the physiology of metabolism and the psychol- 

 ogy of the thought, or idea, can well be maintained, if 

 we interpret thought as caused by molecular motion. 

 All the psychic effects, by which the organism main- 

 tains its correspondence with environment, are the ele- 

 ments of psychology, and the molecular motion is the 

 physiology. 



There cannot be two separate independent forces 

 operating in the realm of what is called nature. the 

 one called natural, and therefore evolutionary; and the 

 other, something undefined and not subject to the laws 

 of evolution, nor the result of it. All phenomena, 

 usually called psychical, are one in natural cause, with 

 other interchanges of matter and motion and matter 

 and motion are one in reality, the unity of phenomena 

 having the dual aspect only, of structure and function. 

 Psychical phenomena cease w T hen that interchange of 

 matter and motion ceases. They exist only in connec- 

 tion with nerve molecular motion. Each brain produces 

 its peculiar manifestations for that brain only. These 

 peculiar manifestations or functions are not produced 

 elsewhere nor continued after the disintegration of -the 

 brain, unless by an equivalent quantity and quality 

 of living brain tissue. 



Spencer's definition of an idea is: "A wave of molec- 

 ular motion diffused through them" ("an involved set 

 of nervous plexuses"), "will produce, as its psychical 

 correlative, the components of the conception in due 



