the
possession of a psychological medium. The adaptations that the human
being must make are mainly of a psychological character. Their _form_
may be partly determined by external conditions, but this does not
affect the general truth. Whether we take man in a civilised or in an
uncivilised state we find the important thing about him to be his
relations to his fellows. He is not merely a member of a tribe or a
society, but he thinks that society's thoughts, he feels their emotions,
his individual life is an expression of the psychical life of the group
to which he belongs. And his transactions with nature are an expression
of the ideas and beliefs current in the society of which he is a part.

The recognition of this truth was one of the outstanding contributions
of Herbert Spencer to the science of sociology. Whereas other writers
had stressed the power of the environment, as a purely material thing,
in shaping human institutions, Spencer placed chief stress upon the
emotional and intellectual life of primitive man as determining their
beginnings. He showed how man's feelings and beliefs about himself, and
about his fellows, and about the world of living forces with which he
believed himself to be surrounded, were the all-important factors of
social evolution. And the subsequent history of society has been such
that scientific sociology is very largely the study of the growth and
elaboration of an essentially psychical environment. The lower animal
world--except so far as we allow for the operation of instincts--has,
broadly, only the existence of other animals and the physical
surroundings for its environment. With man it is vastly different. Owing
primarily to language, the environment of the man of to-day is made up
in part of the ideas of men who lived and died thousands of years ago.
The use of clothing and the invention of tools would alone make mind a
dominant fact in human life. But apart from these things, the great fact
of social heredity, in virtue of which one generation enjoys the
acquired culture of preceding generations, and without which
civilisation would have no existence, is a great and dominant _mental_
fact. Our institutions, our customs, are transmitted to us as so many
psychic facts. Every new invention, every fresh culture acquisition, is
helping to strengthen and broaden the psychical environment of man. Each
newcomer is born into it; it moulds his nature and determines his life,
as his own car