in concise outline the Doctrine of Evolution, its
basis in the facts of natural history, and its wide and universal scope.
They fall naturally into two groups. Those of the first part deal with
matters of definition, with the essential characteristics of living
things, and, at greater length, with the evidences of organic evolution.
The lectures of the second group take up the various aspects of human
evolution as a special instance of the general organic process. In this
latter part of the series, the subject of physical evolution is first
considered, and this is followed by an analysis of human mental evolution;
the chapter on social evolution extends the fundamental principles to a
field which is not usually considered by biologists, and its purpose is to
demonstrate the efficiency of the genetic method in this department as in
all others; finally, the principles are extended to what is called "the
higher human life," the realm, namely, of ethical, religious, and
theological ideas and ideals.

Naturally, so broad a survey of knowledge could not include any extensive
array of specific details in any one of its divisions; it was possible
only to set forth some of the more striking and significant facts which
would demonstrate the nature and meaning of that department from which
they were selected. The illustrations were usually made concrete through
the use of photographs, which must naturally be lacking in the present
volume. In preparing the addresses for publication, the verbal form of
each evening's discussion has been somewhat changed, but there has been no
substantial alteration of the subjects actually discussed.

The choice of materials and the mode of their presentations were
determined by the general purpose of the whole course. The audiences were
made up almost exclusively of mature persons of cultivated minds, but who
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, l