ial nature to which we are now to turn, because no individual can exist
without having its life directly influenced, not only by other kinds of
organisms, but even more intimately by other members of its own species.
In a single day's activity we who are citizens of a great metropolis are
forced into contact with almost countless other lives, glancing off from
one and another after influencing them to some degree, and gaining
ourselves some impetus and stimulus from our longer or shorter intercourse
with each of them. Our varied social relations are so many and obvious
that it is quite superfluous to specify them as essential things in human
life. For the very reason that they are so obvious and constitute so large
a part of our daily life, we are in danger of conceiving them to be
exclusively human; we unconsciously regard them as different from anything
to be found elsewhere and quite independent of the biological laws
controlling the human unit.

On the contrary, as we trace the development of social organization from
its earliest rudiments it becomes ever clearer that evolution has been
continuous, and that during later ages there has been no suspension of the
natural laws which earlier produced the human type of organism. The
lessons we have learned are by no means to be ignored from this point
forward; all of our conceptions of human biological history must be kept
in mind, for anything new that we may learn is superadded to the rest,--it
cannot disturb or alter the foundations already laid. It is even more
important to realize that the same scientific method is to be employed
which has been so fruitful heretofore. It has given us interesting facts;
it has indicated the most profitable lines of attack upon one and another
scientific problem; and it has demonstrated the practical value of
accurate knowledge, even of information about the evolutionary process. As
familiarity with the laws of human physiology enables one to lead a more
hygienic and efficient life, and as the results of analyzing the evolution
of mentality make it possible to advance intellectually with greater
sureness, conserving our mental energies for effort along lines
established by hereditary endowment, so now we are justified in expecting
that a clear insight into the origin of our social situation and social
obligations will have a higher usefulness beyond the value of the mere
interest inhering in our new knowledge. Every one is necessarily co