LORD SALISBURY ON EVOLUTION. 573* 



particular quality which, is true only under certain conditions. 

 Further, it raises the thought of choice suggests the notion that 

 Nature may or may not operate in the alleged way. 



It was partly the consciousness that wrong ideas are called up 

 in these ways which led me, when writing The Principles of 

 Biology, to substitute the phrase " survival of the fittest " partly, 

 I say, because, as is shown in 164 of that work, the phrase natu- 

 rally emerges when we contemplate, from a purely physical point 

 of view, the phenomena of life and death in connection with sur- 

 rounding actions. My belief is that had Mr. Darwin used this 

 phrase, many misunderstandings of his theory would never have 

 arisen, and many objections to his inferences would have been 

 excluded. Among other excluded objections would have been 

 that raised by Lord Salisbury, who thinks that, lacking a basis of 

 observed facts, the hypothesis of natural selection has no basis. 

 For if we substitute the phrase "survival of the fittest," it be- 

 comes manifest that the process is a necessary one. To see this 

 it needs but to affirm the opposite and say that the law is sur- 

 vival of the unfittest that those creatures which were fit to live 

 have died, and those have lived which were unfit to live. These 

 statements embody a contradiction. Hence survival of the fittest 

 is inevitable is just as certain a truth as a mathematical axiom, 

 which we accept because the negation of it is inconceivable. 



Heredity, otherwise manifest, being clearly proved by the ex- 

 perience of breeders, survival of the fittest necessarily implies 

 that those individuals which have structures best adapted to 

 their environments, will, on the average, have better adapted pos- 

 terity than the rest ; and that so the fitness to the environment 

 will be maintained. A further unavoidable corollary is that if 

 the habitat changes in character, or if there occurs a migration to 

 another habitat, the most unfitted will disappear in a greater pro- 

 portion than the least unfitted ; and that from destruction of the 

 most unfitted in successive generations, there will result a con- 

 tinually-diminished unfitness to the new habitat, until there is 

 reached a fitness for it. These are inferences which it is impos- 

 sible to escape. 



Whether by this process a particular variation will be perpetu- 

 ated and increased, is quite another question. The answer de- 

 pends on the answer to another question in what degree, all 

 things considered, does the particular variation conduce to main- 

 tenance of life ? But while the survival and multiplication of 

 individuals having some advantageous modification of structure, 

 is not a necessary result, the survival and multiplication of indi- 

 viduals having natures, or aggregates of characters, which best fit 

 them to the requirements of their lives, is a necessary result; and 

 it is a necessary truth that this involves the establishment of a 



