environment.

In all the higher forms this process cannot be kept up
indefinitely. After a while they succumb; they die. The
creature is not equal to the task of indefinite self-renewal.
But continuity of the life process is not dependent upon the
prolongation of the existence of any one individual.
Reproduction of other forms of life goes on in continuous
sequence. And though, as the geological record shows, not merely
individuals but also species die out, the life process continues
in increasingly complex forms. As some species die out, forms
better adapted to utilize the obstacles against which they
struggled in vain come into being. Continuity of life means
continual readaptation of the environment to the needs of living
organisms.

We have been speaking of life in its lowest terms -- as a
physical thing. But we use the word "Life" to denote the whole
range of experience, individual and racial. When we see a book
called the Life of Lincoln we do not expect to find within its
covers a treatise on physiology. We look for an account of
social antecedents; a description of early surroundings, of the
conditions and occupation of the family; of the chief episodes in
the development of character; of signal struggles and
achievements; of the individual's hopes, tastes, joys and
sufferings. In precisely similar fashion we speak of the life of
a savage tribe, of the Athenian people, of the American nation.
"Life" covers customs, institutions, beliefs, victories and
defeats, recreations and occupations.