Mediator Dei

Mediator Dei, a papal encyclical, was issued by Pope Pius XII on 20 November 1947. It was the first encyclical devoted entirely to liturgy. The encyclical suggested new directions and active participation instead of a merely passive role for the faithful in the liturgy, in liturgical ceremonies and in the life of their parish. The encyclical also emphasized the importance of the Eucharist. Mediator Dei is one of the more important encyclicals of Pope Pius XII. The encyclical condemned certain excesses of liturgical reform and stressed the importance of the union of sacrifice and altar with communion, which greatly directed the reforms undertaken during and after Vatican II. It was written in part in response to the liturgical movement under way since early in the 20th century.

Pope Pius defends liturgy as important, sacred and sacramental. Liturgy is more than the sum of liturgical actions and prescriptions. It is an error to think of the sacred liturgy as merely the outward or visible part of divine worship or as an ornamental ceremonial. No less erroneous is the notion that it consists solely in a list of laws and prescriptions according to which the ecclesiastical hierarchy orders the sacred rites to be performed. The encyclical has four parts.

The first part explains the nature, origin and development of liturgy. Liturgy is public worship, an obligation for individuals and communities. Liturgy is outward adoration of God as well as a fountain for personal piety. It originated with the early Church:

The first Christians ... "were persevering the doctrine of the apostles and in communication by the breaking of bread and their prayers." Whenever their pastors could summon a little group of the faithful together, they set up an altar on which they proceeded to offer the sacrifice, and around which were ranged all other rites appropriate for the saving of souls and for the honor due to God.

Through prayer, the members of the Mystical Body of Christ are harmonized and united. The liturgy is regulated by the clergy and hierarchy of the Church. It has divine and human elements. Its human elements result from the teachings of the Church, Church laws, pious usages by the faithful and the development of art and music. It must also be noted, however, that Pius warns strongly against a sense of "liturgical archaeologism", the belief that the most ancient practices are more venerable. He recognizes that liturgy is organic, and to return to the most ancient practices would ignore centuries of liturgical organic development. He goes on to say that:

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