PREFACE 



To the writers of this book the train of ideas out- 

 lined therein has given unity to a host of previously 

 unconnected observations. Personal, social, historical 

 episodes have fallen into place, and one great force, 

 ebbing and flowing throughout the ages, is seen 

 moulding the fate of nations. 



In the hope that the idea of this underlying unity, 

 which has been so helpful to the writers, may prove 

 useful to others, this book has been written. 



To emphasize the importance of inheritance in 

 determining the character and value of each individual, 

 some account is given of recent scientific investigation ; 

 while the pages of history, the composition of contem- 

 porary society, and the returns of the Registrar-General 

 have been drawn upon to trace the eff*ects of heredity 

 on the social organism. 



Cambridge, September 1909. 



