The defences set up by theologians against the scientific advance may be summarised under two heads. It is claimed that the 'facts' of the religious life belong to a world of inner experience, to a state of spiritual development which brings the subject into touch with a super-sensuous world not open to the normal human being, and with which science, as ordinarily understood, is incompetent to deal. In essence this is a very old position, and contains the kernel of 'mysticism' in all ages, from the savage state onward. This position involves a very obvious begging of the question at issue. It assumes that all attempts to correlate religious phenomena with phenomena in general have failed, and that all future attempts are similarly doomed to failure. Of course nothing of the kind has been shown. On the contrary, the aim of the present work is to show that no dividing line can be drawn between those states of mind that have been and are classed as religious, and those that are admittedly non-religious. For various reasons I have dealt almost entirely with those conditions that are admittedly pathological, but I believe it would be possible to prove the same of all normal frames of mind and emotional states. Any human quality may be enlisted in the service of religion, but there are none that are specifically religious. It is a pure assumption that the religious visionary possesses qualities that are either absent or rudimentary in other persons. Human faculty is everywhere identical although the form in which it is expressed differs according to education, the presence of certain dominating ideas, and the general influence of one's environment. To admit the claim of the mystic is to surrender all hope of a scientific co-ordination of life. It is quite fatal to the scientific ideal and involves the re-introduction into nature of a dualism the removal of which has been one of the most marked advantages of scientific thinking. Moreover, whatever views we may hold as to the ultimate nature of 'mind' the dependence of all frames of mind upon the brain and nervous system is now generally accepted. We may hold various theories as to the nature of mind, we may, with the late William James, treat the brain as merely a 'transmissive' organ, but even on that assumption--on behalf of which not a shred of positive evidence has been offered--the frames of mind expressed are determined by the nervous mechanism, and thus the laws of mental phenomena become ultimately the laws of the operation of the nervous system. The 'facts' of the religious life thus become part of the facts of psychology as a whole. Its 'laws' will form part of psychological laws as a whole, and religious experiences must be handed over for examination and classification to the psychologist who in turn relies for help and understanding on various associated branches of science.