Earliest churches in Rome

It has been said that the reason the Pope always faced the people when celebrating Mass in St Peter's was that early Christians faced eastward when praying and, due to the difficult terrain, the basilica was built with its apse to the west. Some have attributed this orientation in other early Roman churches to the influence of Saint Peter's.^[3] However, the arrangement whereby the apse with the altar is at the west end of the church and the entrance on the east is found also in Roman churches contemporary with Saint Peter's (such as the original Basilica of Saint Paul Outside the Walls) that were under no such constraints of terrain, and the same arrangement remained the usual one until the sixth century.^[4] According to Klaus Gamber, in this early layout the people were situated not in the central nave but in the side aisles of the church and, while the priest faced both the altar and east throughout the Mass, the people faced the altar (from the sides) until the high point of the Mass, when they would turn to face east, the direction in which the priest was already facing.^[5] This view is strongly criticized on the grounds of the unlikelihood that, in churches where the altar was to the west, they would turn their backs on the altar (and the priest) at the celebration of the Eucharist.^[6]

Later pre-twentieth-century churches in Rome

It was in the 8th or 9th century that the position whereby the priest faced the apse, not the people, when celebrating Mass was adopted in Rome,^[7] under the influence of the Frankish Empire,^[8] where it had become general.^[9] However, in several churches in Rome, it was physically impossible, even before the twentieth-century liturgical reforms, for the priest to celebrate Mass facing away from the people, because of the presence, immediately in front of the altar, of the "confession" (Latin: confessio), an area sunk below floor level to enable people to come close to the tomb of the saint buried beneath the altar. The best-known such "confession" is that in St Peter's Basilica, but many other churches in Rome have the same architectural feature, including at least one, the present Basilica of Saint Paul Outside the Walls, which, although the original Constantinian basilica was arranged like St Peter's, is oriented since 386 in such a way that the priest faces west when celebrating Mass.

Outside of Rome

The earliest Christian churches were not built with any particular orientation in mind, but by the fifth century it became the rule in the Eastern Roman Empire to have the altar at the east end of the church, an arrangement that became normal but not universal in northern Europe.^[9] The old Roman custom of having the altar at the west end and the entrance at the east was sometimes followed as late as the 11th century even in areas under Frankish rule, as seen in Petershausen (Constance), Bamberg Cathedral, Augsburg Cathedral, Regensburg Cathedral, and Hildesheim Cathedral (all in present-day Germany).^[10] In the east also, the original Constantinian Church of the Holy Sepulchre in Jerusalem had its apse to the west until it was Byzantinized in 1048.^{[11][12][13][14]}

Roman Rite

In the Roman Rite of the Catholic Church, the altar is "the center of thanksgiving that the Eucharist accomplishes" and the point around which the other rites are in some manner arrayed.^[15] Its importance was made evident by Romano Guardini (1885–1968), about whom Robert R. Kuehn wrote: "with him [Guardini] on the altar, the sacred table became the center of the universe" [...] The impact of the sacred action was all the more profound because Guardini celebrated the Mass versus populum – facing the people."^[16]

Anglican

For the majority of its history, ad orientem worship was the norm, apart from a relatively brief period following the Reformation when priests in the Church of England and other churches of the Anglican Communion celebrated the Holy Eucharist standing at the north-end (i.e. the left side) of the communion table, according to the rubric in the Book of Common Prayer. By the 1630s, Archbishop Laud's refors had returned the altar to its traditional eastern position - there was an Elizabethan injunction on the matter, which Laud used to defend his requirement that the communion tables be stood permanently altar-wise at the east end. Thereafter followed a time of back-and-forth, but at the Restoration, altars in the Chapels Royal were restored to their proper positions, and many Cathedrals followed suit, although there was a notable disuniformity from church to church, with the non-conformists having differing views.

When the City of London churches were rebuilt following the great fire, there was a noticiable uniformity in the chancel layouts of the rebuilt churches, with the communion table stood on a marble floor, raised on one or two steps, railed and most backed by a reredos. The shallow depth of these steps meant that the communion table could only be placed altar-wise, that is, facing east in the traditional arrangement. It is thought that this is partly due to Wren being the son and nephew of distinguished Laudian churchmen, who would certainly have had the traditional ad orientem arrangement in their churches.^[19] This also applied to the city churches that survived the fire, such as St Helen, Bishopsgate, which retained its ad orientem orientation until the end of the 20th century. It is thought that celebrations from this period were at the "north end", the celebrant was actually facing east, while standing at the north end of the altar, as the altar arrangements leave little other space for the celebrant to stand. 18th Century Churches also follow suit, with similar altar arrangements to Wren's City Churches, with the baroque church of St Martin-in-the-Fields and the neighbouring Palladian church of St Giles-in-the-Fields both with railed altars at their east ends, preclude any arrangement of the altar other than the eastward position - the sanctuary of the latter (still largely in its original form) is so shallow that the swing of the communion rail gate does not even allow the communion table to be pulled away from the wall (the former has since been enlarged, with a modern stone altar positioned for versus populum celebration)

The rubric was further challenged in the 19th century by the Oxford Movement, many of whose leaders preferred the traditional ad orientem position, - indeed what is considered the "English Use" altar arrangement has curtains on 3 sides of the altar, only allowing the eastward celebration of the Eucharist. The practices reintroduced by the Anglo-Catholic revival soon became the norm throughout the Church of England, with most mainstream parish churches adopting, among other catholic practices, Eucharistic vestments, altar candlesticks and crucifixes, and most 19th century churches being constructed with ad orientem celebration in mind. Notable examples include the 19th century high altar at St Paul's Cathedral by Bodley and Garner constructed in marble with a large marble reredos, and the various Oxford Movement churches such as All Saints, Margaret Street and St Cyprian's, Clarence Gate by Comper, built to a Sarum Rite ideal. In America, the rubric requiring that the priest stand at the north end of the table, facing liturgical South, was removed from the 1928 American Book of Common Prayer (the Church of England never adopted the 1928 prayer book, as it was rejected by parliament). This was controversial, despite many notable 19th century Anglican churches and cathedrals in America had been built to Anglo-Catholic ideals, complete with stone eastward-facing altars and using full Eucharistic vestments, but nonetheless regularized a practice that was already widespread. Praying ad orientem then became common especially at the Gloria Patri, Gloria in Excelsis and Ecumenical creeds in that direction.^[20] However, following the reforms of the Second Vatican Council in the Roman Catholic Church, many mainstream Anglican churches that had re-adopted many of the traditional catholic practices, likewise adopted the reforms of Vatican II. "the course of the last forty years or so, a great many of those altars have either been removed and pulled out away from the wall or replaced by the kind of freestanding table-like altar", in "response to the popular sentiment that the priest ought not turn his back to the people during the service; the perception was that this represented an insult to the laity and their centrality in worship. Thus developed today’s widespread practice in which the clergy stand behind the altar facing the people."^[21] Today, it is not uncommon to find ad orientem celebrations of the Eucharist in more traditional Anglican churches, but the reformed late 20th century Roman Catholic practice of versus populum is undoubtedly more widespread despite never being the historical norm.

Methodist

The United Methodist Book of Worship mandates that:

In our churches, the Communion table is to be placed in such a way that the presider is able to stand behind it, facing the people, and the people can visually if not physically gather around it. The table should be high enough so that the presider does not need to stoop to handle the bread and cup. Adaptations may be necessary to facilitate gracious leadership. While architectural integrity should be respected, it is important for churches to carefully adapt or renovate their worship spaces more fully to invite the people to participate in the Holy Meal. If altars are for all practical purposes immovable, then congregations should make provisions for creating a table suitable to the space so that the presiding minister may face the people and be closer to them.^[22]

Lutheran

In the Lutheran German Mass (Deutsche Messe), Martin Luther, the founder of that denomination, wrote that:

Here [in Wittenberg] we retain the vestments, altar, and candles until they are used up or we are pleased to make a change. But we do not oppose anyone who would do otherwise. In the true mass, however, of real Christians, the altar should not remain where it is, and the priest should always face the people as Christ doubtlessly did in the Last Supper.^[23]

In discussing the Divine Service, Lorraine S. Brugh and Gordon W. Lathrop write that "Many Lutherans, in concert with many other Christians, think that the time of which Luther spoke has indeed come, and that the pastor should preside at the table facting the people, i.e., versus populum. The assembly needs to have a sense that it is gathered around that table, sees and hears what happens there, has a promise of Christ clearly addressed to it, participates in the thanksgiving, and is made into a community through God's gift."^[24] Thus, in the Lutheran Church, many altars are now built to be freestanding. In churches where the former altar attached to the wall cannot be moved, it has often been converted to be used as a credence table, as a "significant new table is set up, closer to the people and standing free".^[25]