We have now arrived at the early middle ages. From this time forward there is little to chronicle of the nature of change in the order of the Mass itself which had become a sacred and inviolable inheritance,its origin forgotten. It was popularly believed to have been handed down unchanged from the Apostles, or to have been written by St. Peter himself. Dr. Fortescue considers that the reign of St. Gregory the Great marks an epoch in the history of the Mass, having left the liturgy in its essentials just as we have it today. He writes:

There is, moreover, a constant tradition that St. Gregory was the last to touch the essential part of the Mass, namely the Canon. Benedict XIV (1740­ 1758) says: "No pope has added to or changed the Canon since St. Gregory."

Whether this is totally accurate is not a matter of great importance, and even if some very minor additions did creep in afterwards, perhaps a few Amens, the important point is that a tradition of more than a millennium certainly existed in the Roman Church that the Canon should not be changed. According to Cardinal Gasquet:

This fact, that it has so remained unaltered during thirteen centuries, is the most speaking witness of the veneration with which it has always been regarded and of the scruple which has ever been felt at touching so sacred a heritage, coming to us from unknown antiquity."

Although the rite of Mass did continue to develop after the time of St. Gregory, Doctor Fortescue explains that:

All later modifications were fitted into the old arrangement, and the most important parts were not touched. From, roughly, the time of St. Gregory we have the text of the Mass, its order and arrangement, as a sacred tradition that no one has ventured to touch except in unimportant details.

Among the later additions:

The prayers said at the foot of the altar are in their present form the latest part of all. They developed out of medieval private preparations and were not formally appointed in their present state before the Missal of Pius V (1570)."

They were, however, widely used well before the Reformation and are found in the first printed edition of the Roman Missal (1474).

The Gloria was introduced gradually, at first only to be sung on feasts at bishop's Masses. It is probably Gallican. The Creed came to Rome in the 11th century. The Offertory prayers and the Lavabo were introduced from beyond the Alps hardly before the 14th century. The Placeat, Blessing and the Last Gospel were introduced gradually in the Middle Ages."

These prayers almost invariably have a liturgical use stretching back centuries before their official incorporation into the Roman rite. The Suscipe sancte Pater can be traced back to the prayer book of Charles the Bald (875­877).

The prayers which came into the Roman Mass after the time of Gregory the Great were among the first to be abolished by the Protestant Reformers. The included the prayers said at the foot of the altar, the Judica me, with its reference to the priest going to the altar of God, and the Confiteor with its request for the intercession of Our Lady and the saints were particularly unacceptable. The Offertory prayers, with their specifically sacrificial terminolgy, and the Placeat tibi which comes after the Communion, were totally incompatible with Protestant theology.

The fact that these prayers were incompatible with the Protestant heresy is hardly surprising as one of the reasons which must have prompted the Church to accept them, guided by the Holy Ghost, is the exceptional clarity of their doctrinal content. This tendency for a rite to express ever more clearly what it contains is in perfect accord with the principle lex orandi, lex credendi. This principle has been explained very clearly by Dom Fernand Cabrol,in the introduction to his edition of the Daily Missal:

A pope in the fifth century, in the course of a famous controversy, pronounced the following words which have been regarded, ever since, as an axiom of theology: Legem credendi lex statuat supplicandi (let the law of prayer fix the law of faith)­in other words, the liturgy of the Church is a sure guide to her teaching.

Above all else the Church prizes the integrity of the faith of which she is the guardian: she could not therefore allow her official prayer and worship to be in contradiction with her doctrine. Thus, she has ever watched over the formulae of her liturgy with the utmost care, correcting or rejecting anything that seemed to be in any way tainted with error.

The liturgical books are, therefore, an authentic expression of the Catholic faith, and are, in fact, a source from which theologians may, in all security, draw their arguments in defense of the faith. The liturgy holds an important place among the loci theologici (theological sources), and in this respect its principal representative is the Missal. The latter is not, of course, a manual of Dogmatic Theology, and it is concerned with the worship of God and not with the controversial questions. It is nonetheless true that in the Missal we have a magnificent synthesis of Christian doctrine­the Holy Eucharist, Sacrifice, prayer Christian worship, the Incarnation, and Redemption, in fact, in it all dogmas of the Faith find expression.

In the authoritative exposition of Catholic doctrine edited by Canon George Smith it is stated that:

Throughout the history of the development of the sacramental liturgy, the tendency has always been towards growth,additions and accretions, the effort to obtain a fuller, more perfect, more clearly significant symbolism.