MENTAL EVOLUTION OF MAN 217 



formations to take place, for they do take place in the 

 vast majority of human beings; when they do not, 

 in cases where the brain fails to mature, we speak of 

 unnatural or diseased minds. 



The third division of our evidence relating to mental 

 evolution constitutes what we have called the palaeon- 

 tology of mind. By this term we mean the study of 

 human minds of the past as we may know them through 

 the many varied relics and documents which indicate 

 their characters. It is only too obvious to every one 

 that human knowledge has advanced in the course 

 of time and that every department of human thought 

 and mental activity has participated in this progress. 

 No one would have the temerity to assert that we know 

 nothing more than our ancestors of 5000 or even 1000 

 years ago. Our common-sense teaches us even before 

 the man of science produces the full body of evidence 

 at his disposal that human faculties have evolved. 

 With regard to reasoning powers, which form one of the 

 four distinguishing characteristics of the human species 

 as contrasted with other animals, the case has already 

 been reviewed, and we now turn to speech and language 

 and other departments of human mentality. When 

 we compare the attainments of present day men with 

 the abilities and ideas of their ancestors we will do for 

 mental phenomena precisely what was done when we 

 -compared the skeletons of modern animals with those 

 of creatures belonging to bygone geological ages; in 

 this reason is found the justification for the phrase 

 employed in the present connection. 



