INTRODUCTION 7 



we shall find, whatever may have been our previous 

 political or social creed, our preconceived ideas suffering 

 startling changes. The first care must always be to ask 

 with regard to each proposal, " Will it tend to favour 

 the growth of those elements of the population which 

 already are known to be of national worth ? " " Will 

 it tend to check the reproduction of those whom the 

 present fragmentary knowledge already points out as 

 detrimental to the community ? " " Will it help to 

 increase our knowledge of mankind, so that we shall 

 be able more certainly to separate the sheep from the 

 goats, and to discover what elements among the people 

 are best and most worthy of encouragement ? " 



For at every stage of our inquiry the cry for more 

 knowledge becomes insistent. We are still in compara- 

 tive darkness, and must walk warily in consequence. 

 Direct action at present can be applied safely only at 

 points clear even in the twilight. Our greatest need is 

 for more light. 



In all stages of natural development, living beings 

 are subject to a competitive struggle in which the 

 fitter for that struggle gain an advantage. The 

 race is to the swift and the battle to the strong and 

 skilful. 



Whether or no this fight for life has led to the pro- 

 duction and separation of distinct species in the exact 

 manner suggested by Darwin, without doubt it has 

 modified and is modifying the character of existing 

 types. But the essence of natural selection consists in 

 the conjunction of success in the struggle for life and 

 its fruits with a preponderating rate of reproduction. 



