" The Origin of Species " 447 



finally because of the influence it would exert on the whole con- 

 ception of existence. He wrote in his note-book in the year 1837: 

 "My theory would give zest to recent and fossil comparative anatomy; 

 it would lead to the study of instinct, heredity, and mind-heredity, 

 whole [of] metaphysics^" 



We can distinguish four main points in which Darwin's investiga- 

 tions possess philosophical importance. 



The evolution hypothesis is much older than Darwin ; it is, indeed, 

 one of the oldest guessings of human thought. In the eighteenth 

 century it was put forward by Diderot and Lamettrie and suggested 

 by Kant (1/86). As we shall see later, it was held also by several 

 philosophers in the first half of the nineteenth century. In his preface 

 to The Origin of Species, Darwin mentions the naturalists who were 

 his forerunners. But he has set forth the hypothesis of evolution in 

 so energetic and thorough a manner that it perforce attracts the 

 attention of all thoughtful men in a much higher degree than it did 

 before the publication of the Origin. 



And further, the importance of his teaching rests on the fact that 

 he, much more than his predecessors, even than Lamarck, sought a 

 foundation for his hypothesis in definite facts. Modern science began 

 by demanding — with Kepler and Newton — evidence of verae causae ; 

 this demand Darwin industriously set himself to satisfy — hence the 

 wealth of material which he collected by his observations and his 

 experiments. He not only revived an old hypothesis, but he saw the 

 necessity of verifying it by facts. Whether the special cause on which 

 he founded the explanation of the origin of species — Natural Selection 

 — is sufficient, is now a subject of discussion. He himself had some 

 doubt in regard to this question, and the criticisms which are directed 

 against his hypothesis hit Darwinism rather than Darwin. In his 

 indefatigable search for empirical evidence he is a model even for 

 his antagonists : he has compelled them to approach the problems of 

 life along other lines than those which were formerly followed. 



Whether the special cause to which Darwin appealed is sufficient 

 or not, at least to it is probably due the greater part of the influence 

 which he has exerted on the general trend of thought. "Struggle 

 for existence" and "natural selection" are principles which have 

 been applied, more or less, in every department of thought. Recent 

 research, it is true, has discovered greater empirical discontinuity — 

 leaps, "mutations" — whereas Darwin believed in the importance of 

 small variations slowly accumulated. It has also been shown by the 

 experimental method, which in recent biological work has succeeded 

 Darwin's more historical method, that types once constituted possess 

 great ixsruianence, the fluctuations being restricted within clearly 



* Life and Letters of Charles Darwin, Vol. i. p. 8. 



