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 naturally emerges when we contemplate, from a purely physical point of view, the phenomena of life and death in connection with surrounding 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 becomes manifest that the process is a necessary one. To see this it needs but to affirm the opposite and say that the law is survival 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 experience 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 posterity 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 proportion than the least unfitted; and that from destruction of the most unfitted in successive generations, there will result a continually-diminished unfitness to the new habitat, until there is reached a fitness for it. These are inferences which it is impossible to escape.
Whether by this process a particular variation will be perpetuated and increased, is quite another question. The answer depends on the answer to another question—in what degree, all things considered, does the particular variation conduce to maintenance 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 individuals 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
