The altar, centrally located in the sanctuary, is to be the focus of attention in the church. At the beginning of the Roman Rite of Mass, the priest first of all reverences the altar with a kiss and only after that goes to the chair at which he presides over the Introductory Rites and the Liturgy of the Word. Except in Solemn Mass, a priest celebrating Tridentine Mass (use of the 1962 version of which is by the 7 July 2007 motu proprio Summorum Pontificum still authorized for use both privately and, under certain conditions, publicly) remains at the altar the whole time after saying the Prayers at the Foot of the Altar.
The rite of dedication of a church includes that of the altar of the church and celebration of Mass on that altar is "the principal and the most ancient part of the whole rite" in accordance with the saying of the Fathers of the Church: "This altar should be an object of awe: by nature it is stone, but it is made holy when it receives the body of Christ. In Greek and some other languages used in the Byzantine Rite, the same word ( in Greek) is used for an altar (in general) and for the area surrounding it; that is to say, the entire sanctuary. To refer unambiguously to the altar itself the terms "Holy Table" (Greek ? ?) or "Throne" (chu Prestól) are used.
In the Roman rite, the celebration of the Eucharist in a sacred place such as a church is to take place on an altar; however, outside a sacred place, it may take place on a suitable table, always with the use of a cloth, a corporal, a cross, and candles.
Augustin Joseph Schulte says that Pope Sixtus II (257-259) was the first to prescribe that Mass should be celebrated on an altar, and that there are accounts according to which Saint Lucian of Antioch celebrated Mass on his breast whilst in prison (312), and Theodore, Bishop of Tyre on the hands of his deacons.
Early Christians faced east at prayer, a practice witnessed to by Clement of Alexandria (c. 150 - c. 215), Tertullian (c. 160 - c. 220), and Origen (c. 185 - 253). Churches were generally built with an east-west axis. In the earliest churches in Rome the altar stood at the west end and the priest stood at the western side of the altar facing east and facing the people and the doors of the church. Examples are the Constantinian St. Peter's Basilica and the original Basilica of Saint Paul Outside the Walls. In the East, early churches had the altar at the east end and the priest, facing east, stood at the western side of the altar, with his back to the people and the doors. This later became the common practice also in western Europe. It was adopted in Rome only in the 8th or 9th century. In the succeeding centuries the eastward position in prayer was abandoned, as to a large extent was also, especially in cities, choice of an east-west axis for church buildings, and the end, furthest from the main door, in which the altar stood, could be oriented towards any point of the compass, although by convention churches are always described as though the altar is at the east end, the terms liturgical east and west often being used.
The churches that Christians built after the legalization of their religion in the Roman Empire were not modelled on pagan temples, which were not intended to accommodate large numbers of people. The model used was that of the public basilicas that served for meetings such as sessions of law courts. These were generally spacious, and the interior was divided by two or four rows of pillars, forming a central nave and side aisles. At the end was a raised platform, often situated in an apse, with seats for the magistrates. In basilica-style Christian churches the apse was reserved for the bishop and his clergy; the faithful occupied the centre and the side aisles, and between the clergy and people stood the altar.
Originally a church had only one altar. Ignatius the Martyr, Cyprian, Irenaeus, and Jerome, speak of the altar in the singular. Later, side chapels were added and an altar placed in each. Gregory the Great sent relics for four altars to Palladius, Bishop of Saintes, France, who had placed in a church thirteen altars, four of which remained unconsecrated for want of relics. This is still the practice in the East, where concelebration never ceased to be practised. In the West, the introduction of the celebration by each priest individually gave rise to the need for several altars in some churches, particularly in monasteries. With the reintroduction of concelebration since the Second Vatican Council and the reintroduction of concelebration, there is no longer a need for a multiplicity of altars in the main body of a church. Hence, "in building new churches, it is preferable for a single altar to be erected, one that in the gathering of the faithful will signify the one Christ and the one Eucharist of the Church. In already existing churches, however, when the old altar is so positioned that it makes the people's participation difficult but cannot be moved without damage to artistic value, another fixed altar, skillfully made and properly dedicated, should be erected and the sacred rites celebrated on it alone. In order that the attention of the faithful not be distracted from the new altar, the old altar should not be decorated in any special way."
The earliest altars for celebrating the Christian Eucharist were of wood and identical in form with ordinary house tables, as was doubtless used at the Last Supper. The only such ancient wooden table still preserved is in the Lateran Basilica, and fragments of another are preserved in the Santa Pudenziana church in Rome. A tradition that lacks convincing evidence says that Saint Peter celebrated the Eucharist on both. Optatus of Mileve reproves the Donatists for breaking up and using for firewood the altars of the Catholic churches, and Augustine of Hippo reports that Bishop Maximianus was beaten with the wood of the altar under which he had taken refuge.
St. Helena (c. 250 - c. 330) gave golden altars ornamented with precious stones to the original Church of the Holy Sepulchre. Pulcheria (398 or 399 - 453), sister of Theodosius II, presented an altar of gold to the Basilica of Constantinople. Popes Sixtus III (432-440) and Hilary (461-468) presented several altars of silver to the churches of Rome.
Gregory of Nyssa (c. 335 - c. 395) speaks of the consecration of an altar made of stone (De Christi Baptismate). Since wood is subject to decay, the baser metals to corrosion, and the more precious metals were too expensive, stone became in course of time the ordinary material for an altar. The earliest decree of a council prescribing that an altar which is to be consecrated should be of stone is that of the provincial council of Epeaune (Pamiers), France, in 517.
The present discipline of the Latin Church distinguishes between the "table" of an altar (the top) and the supports or base. The latter, provided it is dignified and solid, may be of any material. On the other hand, "in keeping with the Church's traditional practice and with what the altar signifies, the table of a fixed altar should be of stone and indeed of natural stone", except where the episcopal conference authorizes the use of another material (such as wood) that is dignified, solid and well-crafted. "A movable altar may be constructed of any noble and solid material suited to liturgical use, according to the traditions and usages of the different regions." In Eastern Christianity (including the Eastern Catholic Churches) the use of stone, wood or metal is permitted.
The usage of celebrating the Eucharist on the tombs of martyrs is by the Liber Pontificalis ascribed, probably mistakenly, to Pope Felix I (269-274). According to Johann Peter Kirsch the usage is likely to have preceded Pope Felix and to have concerned the celebration of Mass privately in the underground cemeteries known as the catacombs: the solemn celebration of the martyrs took place in the above-ground basilicas built over their place of burial.
Within the catacomb crypts the Eucharist could be celebrated on a stone slab placed over the grave or sarcophagus of one or more martyrs within a space hollowed out of the tufa walls so as to form an arch-like niche. Both in the catacombs and in the above-ground churches the altar could also be a square or oblong block of stone resting on one or more columns (up to six) or on a masonry structure that enclosed the relics of martyrs. Instead of masonry, upright stone slabs could be used, thus forming, with the top slab, a stone chest containing the relics. This no doubt brought about both a change of form, from that of a simple table to that of a chest or tomb.
Latin Church liturgy, before the reforms of the second half of the twentieth century, had complex rules about a distinction between a "fixed altar" and a "portable altar". The former term then meant an altar table (the top slab) with its supports, all of which had been consecrated as a single unit, while the latter term meant the (usually small) altar stone or any altar table consecrated separately from its supports.
These rules no longer hold: today "an altar is said to be fixed if it is so constructed as to be attached to the floor and not removable; it is said to be movable if it can be displaced."
Usually an altar should be fixed and ritually dedicated, but a mere blessing is sufficient for a movable altar. In a church a fixed altar is desirable, but in other places set aside for sacred celebrations the altar may be movable.
The practice of celebrating the Eucharist over the graves of martyrs is probably the origin of the rule that demanded that every altar must contain the relics of martyrs.
The General Instruction of the Roman Missal states that "the practice of the deposition of relics of Saints, even those not Martyrs, under the altar to be dedicated is fittingly retained. However, care should be taken to ensure the authenticity of such relics."
The Caeremoniale Episcoporum adds: "Such relics should be of a size sufficient for them to be recognized as parts of human bodies; hence excessively small relics of one or more saints must not be placed beneath the altar. The greatest care must be taken to determine whether the relics in question are authentic; it is better for an altar to be dedicated without relics than to have relics of doubtful authenticity placed beneath it. A reliquary must not be placed upon the altar or set into the table of the altar; it must be placed beneath the table of the altar, as the design of the altar permits."
In earlier centuries minute portions of relics were inserted into the table of the altar and also into the altar stones that at that time were called movable altars. The cavity into which they were placed was called the sepulchrum (Latin for "tomb"). The relics could be of several saints, but two had to be martyrs until 1906, when the Congregation of Rites decided that it was sufficient to enclose relics of two canonized saints of whom one was a martyr. The relics were placed in a reliquary of lead, silver, or gold, large enough to contain also three grains of incense and a small attestation of consecration on a piece of parchment. In an altar stone, the relics were inserted directly, without a reliquary. There were precise rules also about where exactly in the altar the relics were to be placed and about the stone cover for the cavity.
In ancient churches in which the altar is built over the tomb of a saint or over the relics that have been placed there, a niche below the altar offered a view of the tomb or reliquary and allowed the faithful to touch it and to place in contact with it that would then be venerated as second-class relics. The best known example is the Niche of the Palliums in St. Peter's Basilica in the Vatican. It is now approached by descending steps, since the present floor is considerably higher than that of the original basilica. Other churches also have in front of the altar a similar semicircular hollow area, known as the confessio, even if the altar is not built over a holy tomb, as in the Lateran Basilica and the Basilica di Santa Maria Maggiore.
"The sanctuary is the place where the altar stands, the Word of God is proclaimed, and the Priest, the Deacon, and the other ministers exercise their functions. It should be appropriately marked off from the body of the church either by its being somewhat elevated or by a particular structure and ornamentation. It should, moreover, be large enough to allow the Eucharist to be easily celebrated and seen."
The sanctuary or chancel or presbytery, as well as being elevated above the floor level of the rest of the church, is often, though less frequently than in the past, demarcated by altar rails (sometimes called a communion rail). In ancient churches such wooden or metal railings were called cancelli or, if of marble slabs, transennae.
In Eastern Catholic Churches of Byzantine tradition, the sanctuary is usually cut off from the view of the congregation by an iconostasis, and in those whose tradition is that of Oriental Orthodoxy, such as the Armenian Catholic Church, a curtain may hide it from view at certain points of the liturgy.
The altar may also be marked with a surmounting ciborium, sometimes called a baldachin.
Christian altars were not at first placed on steps. Those in the catacombs stood on the pavement. The altars of churches in Rome were usually erected over the confessio or , the spot where the remains of a martyr were deposited. By the fourth century they were placed on one step above the floor of the sanctuary.
Later, the number of steps was increased. It became the norm that the main altar of a church should be raised above the level of the sanctuary by three steps, while side altars had a single step. The papal altar in St Peter's Basilica in the Vatican is approached by seven steps.
An odd number was always chosen. Since it was considered proper to use the right foot in taking a first step, this ensured that the priest, having ascended the first of the steps with his right foot would also enter the predella (the platform or footpace on which the altar stood) with his right foot. The same rule applied to pre-Christian temples, as indicated by Vitruvius in his De architectura: "The number of steps in front should always be odd, since, in that case, the right foot, which begins the ascent, will be that which first alights on the landing of the temple." The Satyricon attributed to Petronius also mentions the custom of dextro pede (right foot first).
In late medieval and Tridentine times, elaborate rules were developed not only about the number of steps, but also about the material used, the height of each step, the breadth of the tread, the covering with carpets or rugs (both of which were to be removed from the stripping of the altars on Holy Thursday until just before the Mass on Holy Saturday morning, and the carpet alone at a Requiem Mass), and the colour and design of the carpet. On these matters articles by Augustin Joseph Schulte in the 1907 Catholic Encyclopedia may be consulted.
The present General Instruction of the Roman Missal makes no mention of altar steps or carpets.
Early extant ciboria in Ravenna and Rome usually consist of four columns topped by a pyramidal or gabled roof. On some, rods between the columns indicate that they were provided with curtains that could be closed at certain points of the liturgy, as is the custom in the Armenian and Coptic Rites. Some later churches without a ciborium hung a curtain on the wall behind the altar, with two curtain-bearing rods extending at the sides of the altar. From at latest the 4th century, the altar was covered from the view of the congregation at points during Mass by altar curtains hanging from rods supported by a ciborium, riddel posts, or some other arrangement. This practice declined as the introduction of other structures that screened the altar, such as the iconostasis in the East and rood screen and pulpitum in the West, meant that the congregation could barely see the altar anyway.
In early times, before the break-up of the Roman Empire exposed such objects to sacking and looting, the consecrated bread of the Eucharist (the reserved sacrament) was kept in a gold or silver dove, sometimes enclosed in a silver tower, suspended by fine chains from the ciborium that sheltered the altar.
Instead of a four-column ciborium a movable canopy (called a tester) was in some churches suspended from the ceiling above the altar or a fixed canopy attached to the wall was employed.
In medieval churches the altar, no longer standing between priest and people, grew considerably in size. The bishop's seat was moved to one side and the elaborate altar was placed against, or at least close to, the wall of the apse.
The Roman Missal of Pope Pius V, whose use was made generally obligatory throughout the Latin Church in 1570 laid down that, for Mass, a cross should be placed in the middle of the altar, flanked by at least two candlesticks with lit candles, and that the central altar card should be placed at the foot of the cross. It stated also that "nothing whatever unrelated to the sacrifice of the Mass and the adornment of the altar itself is to be placed on it".
Although the Roman Missal thus spoke of the cross and the candlesticks as on the altar, it became customary to add to the edge of altars one or more steps, slightly higher than the altar itself, on which to place the crucifix, candlesticks, flowers, reliquaries, and other ornaments. These adjuncts became common when, in the sixteenth century, church tabernacles were added to altars, requiring that most of the altars concerned be provided with these superstructures, which are known as altar ledges, degrees, gradini or superstructural steps.
21st-century altars are generally freestanding and have no superstructures.
During much of the second millennium, altars in western Europe, which for the most part were then placed close to a wall or attached to it were often backed by a painting or sculpture that visually seemed to form a single unit with the altar.
The term "altarpiece" is applied very widely to them. A reredos is normally a quite large altarpiece placed on the ground between the altar and the wall and can include paintings or sculptures and may even hold stands for flowers and candlesticks. A retable is normally placed on the altar itself or on a stand behind it or may be attached to the wall. Such an artwork is sometimes called a dossal, a term often reserved instead for an ornamental cloth hanging behind the altar. A painting or a mosaic on the wall can serve the same purpose as a removable altarpiece.
An altarpiece may be a single painting or a composition of several panels placed side by side. Especially in the latter case, a series of smaller-scale paintings may act as a kind of base for the main images. This base is called the predella (not to be confused with the same term when used of the platform on which the altar sits), and may illustrate episodes in the life of the saint whom the altar celebrates.
Some altarpieces are known as winged altarpieces. In these the fixed central panel is flanked by two or more hinged panels, which can be moved to hide the central painting and the paintings on the side-panels themselves, leaving visible only the reverse of the side-panels, which are usually relatively plain. They can then be opened to display the images on feastdays. According to the number of panels, these are called triptychs (if of three panels) or polyptychs (if the panels are more than three).
For the celebration of Mass, the altar should be covered by at least one white altar cloth: "Out of reverence for the celebration of the memorial of the Lord and for the banquet in which the Body and Blood of the Lord are offered, there should be, on an altar where this is celebrated, at least one cloth, white in colour, whose shape, size, and decoration are in keeping with the altar's structure." The pre-1969 regulations prescribed three white altar cloths, the topmost being long enough to reach the ground at both ends. 19th and early 20th-century regulations required that the cloths be of linen or hemp and not of any other material, even if of equivalent or higher quality.
In addition, it was customary to place directly on the altar, beneath the three obligatory altar cloths, a cloth waxed on one side that was called the chrismale or cere cloth and that served to keep the altar cloths dry.
When the altar is not used for a liturgical service, the altar cloths may be protected against being stained or soiled by placing over them an altar protector or altar cover made of cloth, baize or velvet large enough to hang down a little on all sides. This is known as the vesperale or stragulum.
When in the period immediately preceding the late twentieth century altars were generally built attached to or close to a wall, it became customary to cover with drapery the front of the altar, the only part visible to the congregation. This drapery was called the antependium or altar frontal, terms often applied also to sculptural or other ornamentation of the altar front itself. The elaborate rules then prevailing in the Latin Church in its regard are indicated in the article about it in the 1907 Catholic Encyclopedia. It covered the whole front of the altar, partial coverings being forbidden. It was obligatory unless the altar front was particularly artistic, and even in such cases it should be used on more solemn occasions. Its origin was thought to have derived from the curtains or veils of silk or other precious material hanging over the open space under the altar table to preserve the shrine of saints deposited there. In the Middle Ages a similar function was performed by an "altar stole", an ornament in the shape of the ends of a stole attached to the front of the altar.
In the 21st century the altar in a Catholic church is generally left visible.
"On or next to the altar are to be placed candlesticks with lighted candles: at least two in any celebration, or even four or six, especially for a Sunday Mass or a Holyday of Obligation, or if the Diocesan Bishop celebrates, then seven candlesticks with lighted candles [...] The candles [...] may also be carried in the procession at the Entrance."
While only two lighted candles are now obligatory and may be placed beside the altar rather than on it, the pre-1969 rubrics (which did not envisage the candles being brought in the Entrance procession) required that they be on the altar itself (in practice, however, they were often placed on the altar shelf instead) and should be four at a Low Mass celebrated by a bishop, four or six at a Missa cantata, six at a Solemn Mass and seven at a Pontifical High Mass. In the last case, the seventh candle was not lit if the bishop was celebrating outside his own diocese. There were also rules, developed over centuries, about the material from which the candlesticks were to be made and about the relative heights of the candles. Candles appear not to have been placed on the altar before the twelfth century, but earlier writings speak of acolytes carrying candlesticks, which, however, they placed on the floor of the sanctuary or near the corners of the altar, as is still the custom in the Eastern Orthodox Church.
Liturgical books of the same pre-1969 period speak of the placing of flowers (even good-quality artificial ones) in vases between the candlesticks on the altar. The present rule is: "During Advent the floral decoration of the altar should be marked by a moderation suited to the character of this time of year, without expressing in anticipation the full joy of the Nativity of the Lord. During Lent it is forbidden for the altar to be decorated with flowers. Exceptions, however, are Laetare Sunday (Fourth Sunday of Lent), Solemnities, and Feasts. Floral decoration should always show moderation and be arranged around the altar rather than on the altar table. For only what is required for the celebration of the Mass may be placed on the altar table".
Tabernacles began to be placed on altars in the sixteenth century. The 1570 Roman Missal of Pope Pius V did not envisage placing the tabernacle on an altar: it laid down instead that the altar card containing some of the principal prayers of the Mass should rest against a cross placed midway on the altar (Rubricae generales Missalis, XX - De Praeparatione Altaris, et Ornamentorum eius). However, in 1614 Pope Paul V ordered the churches of his diocese of Rome to put the tabernacle on some altar. Whether on the main altar of the church or in a special chapel, the tabernacle became more and more large and ornate, to the extent of dominating the altar.
The present rules are as follows: