BELIEFS
questions can be answered, with perfect justification, in the
affirmative. Certain properties, which it is impossible not
to regard as valuable, have been developed in the course of
evolution. The lower forms of life persist more or less
unchanged; but among the higher forms there has been a
definite trend towards greater control and greater independ-
ence of the physical environment. Beings belonging to the
highest forms of life have increased their capacity for self-
regulation, have created an internal environment capable of
remaining stable throughout very great changes in the
outer world, have equipped themselves with elaborate
machinery for picking up knowledge of the outer world, as
well as of the inner, and have developed a wonderfully
effective instrument for dealing with that knowledge.
Evolutionary progress is of two kinds: general, all-round
progress and one-sided progress in a particular direction.
This last leads to specialization. From the evidence pro-
vided by the study of fossils and living forms, we are justi-
fied in inferring that any living form which has gone in for'
one-sided progress thereby makes it impossible for itself to
achieve generalized progress. Nothing fails like success;,
and creatures which have proved eminently successful in
specializing themselves to perform one sort of task and to *
live in one sort of environment are by that very fact
foredoomed to ultimate failure.
Failure may take the form of extinction, or alternatively,
of survival and adaptive radiation into forms that reach a
relatively stable position and become incapable of further
development, since such development would imperil the
equilibrium existing between the living creature and its
environment. Only one species, of all the millions that
exist and have existed, has hitherto resisted the temptation
to specialize. Sooner or later all the rest have succumbed
and have thus put themselves out of the running in the
evolutionary race. This is true even of the mammals.
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