It is a Religious Book. The book tells that Our knowledge of religion receives contributions from every quarter; even the student of mental diseases finds information that is of service to the student of religion. The reverse is equally true: a knowledge of religion sheds light upon even the science of mental disorders. In this short book, a psychiatrist seeks in the study of one aspect of religious practice the worship of the procreating power to gain a clearer understanding of the forms taken by certain kinds of mental diseases. His theory is that we may expect diseased minds to reproduce, or return to expressions of desire customary and official in societies of lower culture. This is, as a matter of fact, less a theory than a statement of observed facts; of this, the reader of these pages, if familiar with certain mental disorders, may readily convince himself. But Doctor Brown's intention is not merely, perhaps not primarily, to draw the attention of the Psychiatrist to a neglected source of information, he aims at something of wider import and addresses a wider public.