ave here a uniformity resting upon
other causes than the physical uniformity that appears in the
objects with which the natural sciences deal. It would enable
us to establish a second group of uniform phenomena which is
psycho-physical in its character and rests upon the basis of
social suggestion. The uniformities in speech, belief, and
institutions would belong to this second group.[23]

What is true of the comparative study of languages is true in every
other field in which a comparative study of cultural materials has been
made. As soon as these materials are studied from the point of view of
their similarities rather than from the point of view of their
historical connections, problems arise which can only be explained by
the more abstract sciences of psychology or sociology. Freeman begins
his lectures on _Comparative Politics_ with the statement that "the
comparative method of study has been the greatest intellectual
achievement of our time. It has carried light and order into whole
branches of human knowledge which before were shrouded in darkness and
confusion. It has brought a line of argument which reaches moral
certainty into a region which before was given over to random
guess-work. Into matters which are for the most part incapable of
strictly external proof it has brought a form of strictly internal proof
which is more convincing, more unerring."

Wherever the historian supplements _external_ by _internal_ proof, he is
in a way to substitute a sociological explanation for historical
interpretation. It is the very essence of the sociological method to be
comparative. When, therefore, Freeman uses, in speaking of comparative
politics, the following language he is speaking in sociological rather
than historical terms:

For the purposes then of the study of Comparative Politics, a
political constitution is a specimen to be studied, classified,
and labelled, as a building or an animal is studied,
classified, and labelled by those to whom buildings or animals
are objects of study. We have to note the likenesses, striking
and unexpected as those likenesses often are, between the
political constitutions of remote times and places; and we
have, as far as we can, to classify our specimens according to
the probable causes of those likenesses.[24]

Historically sociology has had its origin in history. It owes its
existence as a science to