earth. If then organic beings in a state of nature vary even in a slight
degree, owing to changes in the surrounding conditions, of which we have
abundant geological evidence, or from any other cause; if, in the long
course of ages, inheritable 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 contingencies 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 preserved 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 preservation of varieties and
species in a state of nature. For brevity sake I sometimes speak of natural
selection as an intelligent 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, selection does nothing without
variability, and this depends in some manner on the action of the