MR, DARWIN ON NATURAL SELECTION. 365 



say, indeed, that it is "sometimes" as convenient a 

 term as natural selection ; but the kind of men who 

 exercise permanent effect upon the opinions of other 

 people will bid such a passage as this stand aside some- 

 what sternly. If a term is not appreciably longer than 

 another, and if at the same time it more accurately 

 expresses the idea which is intended to be conveyed, it 

 is not sometimes only, but always, more convenient, and 

 should immediately be substituted for the less accurate 

 one. 



No one complains of the use of what is, strictly 

 speaking, an inaccurate expression, when it is never- 

 theless the best that we can get. It may be doubted 

 whether there is any such thing possible as a perfectly 

 accurate expression. All words that are not simply 

 names of things are apt to turn out little else than com- 

 pendious false analogies; but we have a right to 

 complain when a writer tells us that he is using a less 

 accurate expression when a more accurate one is ready 

 to his hand. Hence, when Mr. Darwin continues, " Who 

 ever objected to chemists speaking of the elective affi- 

 nities of the various elements ? and yet an acid cannot 

 strictly be said to elect the base with which it by 

 preference combines," he is beside the mark. Chemists 

 do not speak of "elective affinities" in spite of there 

 being a more accurate and not appreciably longer ex- 

 pression at their disposal. 



" It has been said," continues Mr. Darwin, " that I 

 speak of natural selection as an active power or deity. 

 But who objects to an author speaking of the attraction 

 of gravity ? Everyone knows what is meant and im- 



