254 THE HISTORY OF CREATION. 
plants, which obtains at any moment, is simply the 
necessary result of the momentary predominance which 
either of these two formative powers (or physiological 
activities) has acquired over the other. 
If we now return to the consideration of the process of 
selection or choice, the outlines of which we have already 
examined, we shall be in a position to see clearly and dis- 
tinctly that both artificial and natural selection rest solely 
upon the interaction of these two formative tendencies. If 
we.carefully watch the proceedings of an artificial selector— 
a farmer or a gardener—we find that only these two con- 
structive forces are used by him for the production of new 
forms. The whole art of artificial selection rests solely upon 
a thoughtful and wise application of the laws of Inheritance 
and Adaptation, and upon their being applied and regulated 
in an artistic and systematic manner. Here the will of man 
constitutes the selecting force. 
The case of natural selection is quite similar, for it also 
employs merely these two organic constructive forces, these 
ingrained physiological properties of Adaptation and Here- 
dity, in order to produce the different species. But the 
selecting principle or force, which in artificial selection is 
represented by the conscious will of man acting for a definite 
purpose, consists in natwral selection of the unconscious 
struggle for existence acting without a definite plan. What 
we mean by “struggle for existence” has already been ex- 
plained in the seventh chapter. It is the recognition of 
this exceedingly important identity which constitutes one 
of the greatest of Darwin’s merits. But as this relation is 
very frequently imperfectly or falsely understood, it is 
necessary to examine it now more closely, and to illustrate 
a 
