A comparison of Christianity with Muhammedanism or with any other
religion must be preceded by a statement of the objects with which
such comparison is undertaken, for the possibilities which lie in this
direction are numerous. The missionary, for instance, may consider
that a knowledge of the similarities of these religions would increase
the efficacy of his proselytising work: his purpose would thus be
wholly practical. The ecclesiastically minded Christian, already
convinced of the superiority of his own religion, will be chiefly
anxious to secure scientific proof of the fact: the study of
comparative religion from this point of view was once a popular branch
of apologetics and is by no means out of favour at the present day.
Again, the inquirer whose historical perspective is undisturbed by
ecclesiastical considerations, will approach the subject with somewhat
different interests. He will expect the comparison to provide him with
a clear view of the influence which Christianity has exerted upon
other religions or has itself received from them: or he may hope by
comparing the general development of special religious systems to gain
a clearer insight into the growth of Christianity. Hence the object of
such comparisons is to trace the course of analogous developments and
the interaction of influence and so to increase the knowledge of
religion in general or of our own religion in particular.

A world-religion, such as Christianity, is a highly complex structure
and the evolution of such a system of belief is best understood by
examining a religion to which we have not been bound by a thousand
ties from the earliest days of our lives. If we take an alien religion
as our subject of investigation, we shall not shrink from the
consequences of the historical method: whereas, when we criticise
Christianity, we are often unable to see the falsity of the
pre-suppositions which we necessarily bring to the task of inquiry: