Reviewing the first-hand declarations of the mystics, we inevitably notice one prominent feature: the frequency with which they break up their experience into three phases. Sometimes they regard these objectively, and speak of three worlds or three aspects of God of which they become successively aware. Sometimes they regard them subjectively, and speak of three stages of growth through which they pass, such as those of Beginner, Proficient, and Perfect; or of phases of spiritual progress in which we first meditate upon reality, then contemplate reality, and at last are united with reality. But among the most widely separated mystics of the East and West this threefold experience can nearly always be traced. There are, of course, obvious dangers in attaching absolute value to number-schemes of this kind. Numbers have an uncanny power over the human mind; once let a symbolic character be attributed to them, and the temptation to make them fit the facts at all costs becomes overwhelming. We all know that the number “three” has a long religious history, and are therefore inclined to look with suspicion on its claim to interpret the mystic life. At the same time there are other significant numbers—such as “seven” and “ten”—which have never gained equal currency as the bases of mystical formulæ. We may agree that the mediæval mystics found the threefold division of spiritual experience in Neoplatonism; but we must also agree that a formula of this kind is not likely to survive for nearly 2000 years unless it agrees with the facts. Those who use it with the greatest conviction are not theorists. They are the practical mystics, who are intent on making maps of the regions into which they have penetrated.