10 INTRODUCTION 



necessary if man was to be man. If the new point of 

 view were to prevail, what would become of free-will, 

 the indispensable basis of every ethical system? 

 Where could we find any guidance for human be- 

 haviour if we gave up the spiritualistic faith ? 



It was naturally more difficult for the exponents 

 of the evolution theory to carry the day on this point 

 than on any other point. Even in these days, when- 

 ever controversies arise as to man's life, his physical 

 or mental needs, this theory has to break its path anew 

 with much difficulty. 



In psychology and in ethics, we are constantly con- 

 fronted by some spiritualistic notions, by some biassed 

 tendencies bequeathed to us by metaphysical philos- 

 ophy. 



The same applies to social science, to history, to po- 

 litical economy and to the practical questions related 

 to them: here again we have to fight superannuated 

 views derived from methods of reasoning which 

 natural science discarded long ago. 



In spite of all, the idea of evolution continues on its 

 forward march and will win the battle in this field as 

 it has won it in others. The odds are more tremen- 

 dous here than anywhere else: we must overcome, not 

 only a natural lack of intellectual courage, but also 

 the conscious hostility of those who wilfully oppose 

 mankind's progress. 



Furthermore, the thorough and logical application 



