were on the whole quite unfamiliar with the technical facts of natural
history. It was necessary to disregard most of the problematical elements
of the doctrine so as to bring out only the basic and thoroughly
substantiated principles of evolution. The course was, in a word, a simple
message to the unscientific; and while it may seem at first that the
discussions of the latter chapters lead to somewhat insecure positions, it
should be remembered that their purpose was to bring forward the proof
that even the so-called higher elements of human life are subject to
classification and analysis, like the facts of the lower organic world.

It may seem that the biologist is straying beyond his subject when he
undertakes to extend the principles of organic evolution to those
possessions of mankind that seem to be unique. The task was undertaken in
the Hewitt Lectures because the writer holds the deeply grounded
conviction that evolution has been continuous throughout, and that the
study of lower organic forms where laws reveal themselves in more
fundamental simplicity must lead the investigator to employ and apply
those laws in the study of the highest natural phenomena that can be
found. Another motive was equally strong. Too frequently men of science
are accused of restricting the application of their results to their own
particular fields of inquiry. As individuals they use their knowledge for
the development of world conceptions, which they are usually reluctant to
display before the world. It is because I believe that the accusation is
often only too well merited that I have endeavored to show as well as
circumstances permit how universal is the scope of the doctrine based upon
the facts of biology, and how supreme are its practical and dynamic
values.

It remains only to state that the present volume contains nothing new,
either in fact or in principle; the particular form and mode of presenting