If we were invited, at the present day, to suggest a means of conserving intact a body of doctrinal definitions and disciplinary law, we should not naturally select some mode of oral transmission as the safest available. Yet this expedient has found much favour in the past. Even among the Jews, with their extreme respect for sacred books, the written word was made of none account by the traditions of expositors. The votaries of the Greek mystic cults deliberately avoided writing down their more important formulae. Several considerations were in favour of this curious policy. There were no scientific canons for the interpretation of written texts; allegorising commentators read their own wild fancies into the plainest sentences. The only way of meeting them was to fall back on the traditional interpretation. We use the texts to test the traditions; but criticism in its early stages pursues the opposite course, and as a natural consequence rates tradition above Scripture. Other reasons which discouraged the use of writing were, first, the fear that no literary skill might be equal to the difficulty of accurate statement; secondly, the natural reluctance of the religious mind to let the deepest truths be exposed to the vulgar scoffs and criticism of the uninitiated; thirdly, some remnant of the primitive superstition that the formulae of a ritual are magic spells, which would lose their potency if published to the world; and, finally, the natural instinct of a sacerdotal class to reserve the knowledge of deepest mysteries to a select inner circle. For all these reasons a jealously guarded tradition, commonly designated as the _arcana_ or _secreta_, was to be found in all the early Christian Churches. To give a few examples: the Apostles' Creed, the distinctive symbol of the Roman Church, was preserved by oral tradition only down to the fourth century, and was not imparted to any catechumen until the time of his baptism. The minute rules of penitential discipline were first committed to writing by Theodore of Tarsus, Archbishop of Canterbury, towards the close of the seventh century; and this innovation was sharply criticised by some ecclesiastical synods. Most remarkable of all is the reluctance of the churches to write down the essential, operative parts of the Mass. Written copies are first mentioned in the fourth century, and it was not until a much later period that the diversities of local tradition were corrected by the issue of a standard text. It might be supposed that the non-existence of official copies was due to the want of any device, such as printing, by which they could be cheaply multiplied. But there is a curious fact which suggests that publication was considered undesirable. One section of the Canon of the Mass was called the secret part (_secretum_), and was recited by the celebrant in an undertone, that it might not become known to the congregation. Similarly, all literary