It is the object of this book to trace out that type of life, that peculiar quality of consciousness, which is called ""mystical,"" from its earliest appearance within Christianity; to estimate, so far as is possible, the true character and origin of the Christian mystic, and define the qualities which differentiate him from those other mystics who have been evolved along lines of spiritual development, Oriental, Neoplatonic, or Mahomedan. It is now acknowledged by many psychologists - amongst whom Leuba and Delacroix are of special importance, since their conclusions are entirely free from theological bias - that the Christian mystic does possess such differentiating characters; and represents, so far as the psychical nature of man is concerned, a genuine species apart... From the Preface