each generation. It is based upon that
of preceding generations; it follows set forms, and is generally
influenced by that network of ideas and beliefs into which we are born
and from which none of us ever completely escapes. Still that is hardly
enough in itself to account for the persistence of supernaturalism.
Assuming that originally there existed what was accepted as good
evidence for the existence of a supernatural, it is hardly credible that
every subsequent generation went on accepting it merely because one
generation received evidence of its existence. As organs atrophy for
want of exercise, so do beliefs die out in time for want of proof. Some
kind of evidence must have been continually forthcoming in order to keep
the belief alive and active. It is not a question of whether the
evidence was good or bad. All evidence, it is important to bear in mind,
is good to some one. The "facts" upon which thousands of people were put
to death for witchcraft would not be considered evidence to anyone
nowadays, but they were once accepted as good ground for conviction.

What kind of evidence is it, then, that has been accepted as proof of
the supernatural? Or, to return to Tylor's definition of religion,
seeing that the belief in spiritual beings has persisted in every
generation, upon what kind of evidence has this belief been nourished?
Various replies might be given to this question, all of which may
contain some degree of truth, or an aspect of a general truth. In the
present enquiry I am concerned with one line of investigation only, one
that has been strangely neglected, but which yet, I am convinced,
promises fruitful results. In other directions it has been established
that a great aid to an understanding of the human organism in times of
health is to study its activities under conditions of disease. Abnormal
psychology is now a recognised branch of psychology in general, and a
glance through almost any recent text-book will show that the two form
parts of a natural whole. The normal and the abnormal are in turn used
to throw light on each other. And it appears to the present writer that
in the matter of religious beliefs a much clearer understanding of their
nature, and also of some of the conditions of their perpetuation, may be
gained by a study of what has happened, and is happening, in the light
of mental pathology.

To some, of course, the bare idea of there being a pathology of religion
will appear an entir