b INTEODXTCTIOK 



conditions, of which we have abundant geological evidence, or 

 from any other cause ; if, in the long course of ages, inherit- 

 able variations ever arise in any way advantageous to any 

 being under its excessively complex and changing relations of 

 life ; and it would be a strange fact if beneficial variations did 

 never arise, seeing how many have arisen which man has taken 

 advantage of for his own profit or pleasure ; if then these con- 

 tingencies ever occur, and I do not see how the probability of 

 their occurrence can be doubted, then the severe and often- 

 recurrent struggle for existence will determine that those 

 variations, however slight, which are favourable shall be pre- 

 served or selected, and those which are unfavourable shall be 

 destroyed. 



This preservation, during the battle for life, of varieties 

 which possess any advantage in structure, constitution, or 

 instinct, I have called Natural Selection; and Mr. Herbert 

 Spencer has well expressed the same idea by the Survival of 

 the Fittest. The term " natural selection " is in some respects a 

 bad one, as it seems to imply conscious choice ; but this will 

 be disregarded after a little familiarity. No one objects to 

 chemists speaking of " elective affinity ; " and certainly an 

 acid has no more choice in combining with a base, than the 

 conditions of life have in determining whether or not a new 

 form be selected or preserved. The term is so far a good 

 one as it brings into connection the production of domestic 

 races by man's power of selection, and the natural preserva- 

 tion of varieties and species in a state of nature. For brevity 

 sake I sometimes speak of natural selection as an intel- 

 ligent power ; — in the same way as astronomers speak of the 

 attraction of gravity as ruling the movements of the planets,, 

 or as agriculturists speak of man making domestic races by 

 his power of selection. In the one case, as in the other, selec- 

 tion does nothing without variability, and this depends in some 

 manner on the action of the surrounding circumstances on the 

 organism. I have, also, often personified the word Nature ; 

 for I have found it difficult to avoid this ambiguity; but I 

 mean by nature only the aggregrate action and product of 

 many natural laws, — and by laws only the ascertained sequence 

 of events. 



