Historical factors played a crucial role in the manner in which the liturgy was celebrated. During times of persecution brevity and simplicity would be its principal characteristics for obvious reasons. The toleration of Christianity under Constantine I, and its adoption as the religion of the Empire under Theodosius I (379-95), had a dramatic effect on the development of ritual. Congregations increased in size; and benefactions for the building and furnishing of churches resulted in the enrichment of vessels and vestments. Those presenting such gifts would naturally want them to be of the richest and most beautiful nature possible. In a parallel and natural development the liturgical rites became more elaborate, with solemn processions and stress upon the awesome nature of the rite. This elaboration of the liturgy proceeded faster and further in the East than in the West during the fourth century, but the universal change in style was initiated throughout the Christian world by the change from an illegal and private ritual into a state-supported public one.

From the fourth century onwards we have very detailed information about liturgical matters. The Fathers such as St. Cyril of Jerusalem (d. 386), St. Athanasius (d. 373), St Basil (d. 379), St. John Chrysostom (d. 407) give us elaborate descriptions of the rites they celebrated. It is unfortunate that we know less about the earliest history of the Roman rite than about any other. The freedom of the Church under Constantine and, roughly, the first general council in 325 (Nicea), mark the great turning point for liturgical study. From about the fourth century complete liturgical texts were compiled, the first Euchologion and Sacramentaries were drawn up for use in church. Tthe Euchologion is the liturgical book of the Eastern Churches containing the Eucharistic rites, the invariable parts of the Divine Office, and the rites for the administration of the Sacraments and Sacramentals, thus combining the essential parts of the Missal, Pontifical, and Rituale in the Roman Rite). By this time, the old fluid uniform rite has crystallized into different liturgies in different places. These different liturgies all bear the marks of their common descent and follow the same general outline. Four parent rites can be discerned to which all existing ancient liturgies can be traced. Three of the parent rites are those of the three old patriarchal cities, Rome, Alexandria and Antioch. The general rule for liturgical usage is that rite followed patriarchate. The fourth parent rite, the Gallican, was an exception to this rule as, although celebrated within the Roman Patriarchate, it was not derived from the rite celebrated in Rome. As this study is concerned only with the evolution of the Roman Rite the liturgies of Alexandria and Antioch will not be examined, but the Gallican Rite will as it had considerable influence upon the development of the finalized Roman Rite.