166 SOCIAL EVOLUTION 



most often along routes predestined by the configuration 

 of the country. But on the other hand, a race that has 

 developed a civilization in some well nourished and pro- 

 tected area falls into decline because the very conditions 

 which gave safety in the earlier period, now isolate the 

 people from the great currents of men and ideas that 

 move along the more accessible river valleys and over 

 the vast and fertile alluvial plains where great cities 

 have arisen, causing exchange of commodities and the 

 contact of minds. If the aspects of nature are terrify- 

 ing and sublime, the explanations that men advance tend 

 to be colored with superstitious fear. When the sur- 

 roundings of the people are awe-inspiring the response 

 to these manifestations of grandeur are fear and rever- 

 ence. This continued response becomes habit in the 

 individual and custom in the group. As the usage is 

 integrated, all those who do not respond to the terrible 

 manifestations of nature with the customary degree of 

 fear and reverence are regarded with suspicion. That 

 is, the confident and the skeptical are constrained. Any 

 attitude of curiosity or criticism is discouraged as es- 

 sentially unrighteous and endangering the safety of the 

 group. For this reason the primitive man persecutes 

 any member of his tribe who, because of a confident or 

 critical turn of mind, deviates too far from the paths 

 prescribed by the established usages of the group. Thus 

 does physical environment set the limits to human habita- 

 tion, guide the movements of aimless migrations, stimu- 

 late or retard the development of civilizations; some- 

 times facilitating the easy communication of ideas and 

 the exchange of goods, and other times impressing the 

 minds of a people with a sense of its grandeur which 



