PREFACE 



In common with a large and increasing number of 

 theological writers who firmly maintain the cathoHc 

 faith, the author of these lectures beHeves that, at the 

 present stage of advance in natural science, the evo- 

 lutionary theory affords the best available working 

 hypothesis of the origin of species; and that this 

 hypothesis is apphcable to the human species in its 

 physical aspects. Whether the evolutionary theory can 

 sustain the test of further scientific investigation and 

 of wider induction — that is, whether it constitutes 

 the final word of science, the lecturer does not pretend 

 to judge. But in the present state of knowledge, it 

 seems presumptuous and futile for one who is not an 

 expert in natural science to join issue with scientists 

 on the subject. 



What we are saying has exclusive reference to the 

 general scientific doctrine that the origin of existing 

 species is to be described on its physical side by natural 

 variations in primitive forms of organic life, by inheri- 

 tance of such variations, and by the persistence of those 

 forms that are best fitted to survive in the struggle for 

 existence. We do not acknowledge that the more 

 specific explanations of evolution, and of its factors, 

 whether Darwinian or other, have attained to the same 

 scientific rank. No one of them can claim general 



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