the universal occurrence of organic adaptation. An animal is not an
independent thing; its life is intertwined with the lives of countless
other creatures, and its very living substance has been built up out of
materials which with their endowments of energy have been wrested from the
environment. Every animal, therefore is engaged in an unceasing struggle
to gain fresh food and new energy, while at the same time it is involved
in a many-sided conflict with hordes of lesser and greater foes. It must
prevail over all of them, or it must surrender unconditionally and die.
There is no compromise, for the vast totality we individualize as the
environment is stern and unyielding, and it never relents for even a
moment's truce.

To live, then, is to be adapted for successful warfare; and the question
as to the mode of origin of species may be restated as an inquiry into the
origin of the manifold adaptations by which species are enabled to meet
the conditions of life. Why is adaptation a universal phenomenon of
organic nature?

The answer to this query given by Darwinism may be stated so simply as to
seem almost an absurdity. It is, that if there ever were any unadapted
organisms, they have disappeared, leaving the world to their more
efficient kin. Natural selection proves to be a continuous process of
trial and error on a gigantic scale, for all of living nature is involved.
Its elements are clear and real; indeed, they are so obvious when our
attention is called to them that we wonder why their effects were not
understood ages ago. These elements are (1) the universal occurrence of
variation, (2) an excessive natural rate of multiplication, (3) the
struggle for existence entailed by the foregoing, (4) the consequent
elimination of the unfit and the survival of only those that are
satisfactorily adapted, and (5) the inheritance of the congenital