MENTAL EVOLUTION OF MAN 203 



infantile and adolescent types of mind become adult 

 intellectuality ; in the third place, in speaking of the 

 palaeontology of mind, the phrase is used to refer to the 

 varied and changing mental abilities of human races in 

 historic and prehistoric times as they may be demon- 

 strated and determined by the evidences of the culture 

 of such earlier epochs. In considering the matter of 

 method, the questions are whether variation, inheritance, 

 and selection are as real in the world of mental phe- 

 nomena as they are in the material world, and whether 

 the laws are the same or similar in the two cases. We 

 shall learn how the results of such studies prove with 

 convincing clearness, first, that the contents of the indi- 

 vidual mind and of the minds of various human races 

 are truly the products of natural evolution, and second, 

 that the human mind differs only in degree from that 

 of lower organisms, and not in kind or fundamental 

 nature. 



When the operations of human mental life are ex- 

 amined, they include what are called processes of 

 reason as apparently distinctive elements. The lower 

 mammalia exhibit a simpler order of " mentality " de- 

 noted intelligence, while the nervous processes of still 

 simpler forms are called instinctive and reflex activities. 

 These are the terms of the comparative array of psy- 

 chology which are to be separately examined and classi- 

 fied, and to be brought into an evolutionary sequence 

 if common-sense directs us to do so. 



Let us begin our comparative study with an example 

 of the simplest animals that consist of only a single cell, 



