In persona Christi

In persona Christi is a Latin phrase meaning "in the person of Christ", an important concept in Roman Catholicism and, similarly or in varying degrees, other Christian traditions, such as Lutheranism, Anglicanism, as well as Eastern Orthodoxy. In Catholic theology, a priest is In persona Christi because, in the sacraments he administers, it is God and Christ who acts through the instrumentality of the priest. An extended term, In persona Christi capitis, “in the person of Christ the head,” was expressed by the bishops of the Vatican Council II in the Decree on the Ministry and Live of Priests, Presbyterorum Ordinis, December 7, 1965.

Roman Catholic understanding

In Roman Catholicism, the priest acts in the person of Christ in pronouncing the words that comprise part of a sacramental rite. For example, in the Mass, the Words of Institution, by which the bread becomes the Body of Christ and the wine becomes the Precious Blood, the priest acts in the person of Christ who is the head of the Church. According to the Catechism of the Catholic Church, the priest in his whole ministry serves as an "icon of Christ", being made fully visible in a particular way when he presides over the celebration of the Eucharist.

Recent history

Code of Canon Law (1983) as modified by Benedict XVI (2009)

The change in Canon Law introduced by Omnium in Mentem resolved a discrepancy between the applicability of in persona Christi Capitis to deacons as well as priests and bishops. With the new Motu Proprio, in persona Christi Capitis applies only to priests and bishops.

Liturgical significance

The doctrine of In persona Christi affects liturgical practice. When a priest speaks to the congregation In persona Christi, the words they speak are the words of God to the Church, rather than the words of humans to God. For example, discussing the conclusion to Mass, the Office for the Liturgical Celebrations of the Supreme Pontiff has said:

Lutheran understanding

In Lutheran practice, when a pastor offers the sacrament of Holy Absolution, he acts in persona Christi. This informs the theology behind the seal of the confessional. Because the priest "acts in Christ’s stead when he absolves a sinner, he acts in Christ’s stead also when he hears a confession." As such, "He may therefore not reveal what Christ Himself does not reveal”."
The rite for private confession and absolution in the Lutheran Service Book, the official hymnal of the Lutheran Church-Missouri Synod, contains the following words of absolution given by the pastor to the penitent:

In the stead and by the command of my Lord Jesus Christ I forgive you all your sins in the name of the Father and of the + Son and of the Holy Spirit.

To which the penitent responds:

Amen.

Eastern Orthodox understanding

Like the Roman Catholic Church, the Eastern Orthodox Church considers a priest to be an icon of Christ both during ministry and in the celebration of the Eucharist. But, their conception, though similar, has traditionally placed more emphasis on the priest's role as a representative the whole people of God during the celebration Eucharist.
The Roman Church does acknowledge the role of the priest's role of offering on behalf of the people, when in the 1993 Catechism it states "...there acting in the person of Christ and proclaiming his mystery, they unite the votive offerings of the faithful to the sacrifice of Christ their head..."