I 



244 DOCTRINE OF EVOLUTION 



profitable lines of attack upon one and another scien- 

 tific problem; and it has demonstrated the practical 

 value of accurate knowledge, even of information about 

 the evolutionary process. As familiarity with the laws 

 of human physiology enables one to lead a more hygienic 

 and efficient fife, and as the results of analyzing the 

 evolution of mentahty make it possible to advance 

 intellectually with greater sureness, conserving our men- 

 tal energies for effort along lines estabhshed by heredi- 

 tary endowment, so now we are justified in expecting 

 that a clear insight into the origin of our social situation 

 and social obligations will have a higher usefulness 

 beyond the value of the mere interest inhering in our 

 new knowledge. Every one is necessarily concerned 

 with social questions; never before has there been so 

 much world-wide discussion of topics in this field. And 

 while it is true that much good may be accomplished 

 in utter ignorance of the past history of human insti- 

 tutions and of the underlying principles which control 

 the varied types of organic associations, surely enlight- 

 ened efforts will be more effective for good. Therefore 

 every member of a community who is capable of think- 

 ing straight rests under an obligation imposed by nature 

 to learn how he is related to his fellow-men ; he must act 

 in concert with them or else he forfeits his rights as a 

 social unit. And it is his clear duty to search among 

 the results of science for aid in ascertaining what he 

 ought to do, and what reasons are given by evolution 

 for the nature of his vital duties. 



Despite the growing appreciation of the fundamental 

 relation between biology and sociology, it is still far 

 from universal. That the latter science is in a sense a 



