Retro Tablum: The Origins and Role of the Altarpiece in the Liturgy
If the event is of a devotional kind all the onlookers direct their eyes with various expressions of devotion towards the event, as when the Host is displayed at the Sacrifice of the Mass.1
An altarpiece is a framed artistic representation of a sacred subject or combination of subjects typically situated behind and above an altar. Though its invention came about in the Middle Ages, the altarpiece is rooted in the ancient Church tradition of employing sacred imagery to enhance the liturgy with visual aids (adiaphora) for the instruction of the faithful; a tradition definitively upheld by the Second Council of Nicaea in the eighth century and by Trent some seven hundred years later. Yet, unlike the altar crucifix or candlesticks, which are appointments prescribed by the Church’s liturgical rubrics, the provision of an altarpiece has never been canonically obligatory.2 Rather, the altarpiece came into existence as a result of particular customs of liturgical and devotional practice; its formal development was shaped by vernacular traditions in Christian sacred art. Hence, as a highlighted survey of its emergence ought to illustrate, the altarpiece is an artistic device derived from earlier conventions of sacred imagery employed to visually reinforce the Catholic understanding of and devotion to the Eucharist and the communion of saints.
Early Forms of Sacred Imagery at the Altar
The Imperial church-building program ushered in by Constantine employed fixed freestanding altars and sacred imagery, which can be traced from the palimpsest of patristic artifacts and decoration, as well as from contemporary textual accounts, such as the Liber Pontificalis. The organization of sacred imagery around the altar was greatly affected by the position of the altar relative to the presbyterium, the part of the church reserved for the bishop and his clergy. Since altars in early Western churches often stood in front of the presbyterium, this position would have likely precluded the possibility of situating any large-scale works of art that would have eclipsed the bishop’s cathedra or faldstool. However, the triumphal arch and hemi-dome of the apse typically featured extensive decorative programs depicting Christ accompanied by a retinue of holy figures including the titular saint of the church, the Apostles, and the Evangelists, as exemplified by the oldest parts of the apse mosaic in Santa Pudenziana in Rome. Yet, sacred symbols and figures also came to be incorporated into the ciborium, the monumental fixed canopy that sheltered the altar, and in the antependium, the ornamental appendage affixed to the vertical supports of the altar. Antependia were designed to extend across the entire altar front, from the underside of the table top (mensa) to the altar step (predella), and were sometimes applied to the back and side faces of the altar as well. Comprised of precious metals, ivory, wood, or rich brocades, and usually bejeweled, the principal subject of early medieval antependia was Christ in Majesty, often flanked by angels, the Evangelists, and the Apostles. In the ninth and tenth centuries, the repertory grew to include the Virgin and Child, as well as titular saints.3 Episodic narratives from the life of Christ or the titular saint were then often disposed symmetrically on either side of the principal subject. The lavish and analogous sacred imagery of early medieval Gospel covers with that of antependia is striking, and, as a note of observation, it would seem that these largely parallel decorative formats were intended to stress the liturgical relationship between Christ’s presence in the Word and the Eucharist.
The fifteenth century high altar retable in the pilgrimage church of Saint Wolfgang in Austria by Michael Pacher contains representations from the life of Christ and the church’s titular, Saint Wolfgang, with the Coronation of the Virgin at the center. Photo: wikimedia.org/Public Domain
Engaged Altars, Reliquaries, and Gradines
The engaged altar emerged from the introduction of the private Mass. The separate oratories that had been established in proximity to Western churches for the celebration of private Masses by individual canons or monks began to be subsumed into the bodies of those churches at least as early as the sixth century, and led to the gradual proliferation of chapels and side altars.4 Side altars were the first to be set against the walls of the church, a gesture in deference to the principal or high altar, which generally remained freestanding well into the Middle Ages. Without a ciborium above or a richly decorated apse beyond, the wall to which the side altar was engaged became the spatial and visual terminus, so that its decoration would seem a natural consequence.
The trend of building engaged side altars for private Masses was notably promoted in the early ninth-century plan of the Abbey of Saint Gall and was accompanied by an ever-growing use of reliquaries during the liturgy. Majesty images, made of precious materials and outwardly depicting the holy figures whose relics they contained, were popular throughout the West, particularly north of the Alps. One of the oldest and best surviving examples of a majesty image is the golden likeness of Saint Fides in Conques-en-Rouergue (France). Majesty images usually were placed behind and above an altar dedicated to the portrayed saint in a niche or on a low ledge known as a gradine, but never directly on the altar during the Mass, and were removed after its conclusion.5 However, by the eleventh century, it was not uncommon for a reliquary or holy image to remain exposed on a gradine outside of liturgical celebrations for popular devotion.6 The fixed-in-place reliquary that developed out of this custom assumed an increasingly architectonic form richly decorated with multiple figures and episodic narratives, epitomized by the Shrine of the Three Kings begun by the twelfth-century goldsmith, Nicholas of Verdun, for Cologne Cathedral.
Emergence of the Altarpiece
The altarpiece is a broad category that includes both fixed and portable works of art, as well as painted or sculpted works. In the English-speaking world, an altarpiece may be referred to as a retable, a generic term derived from the Latin retro tablum, meaning behind the (altar) table, or as a reredos, a term with a similar Latin etymology, but used primarily by Anglophones to connote the fixed, screen-like type into which the altar itself was engaged.7 Retables, like reliquaries, were usually set in place on a gradine behind the altar, whereas reredoses with integral gradines were often freestanding or attached to a wall. Though a base, body, and frame typically comprised the fundamental structure of a retable or reredos, the form, media, and content of altarpieces varied culturally according to local traditions of religious devotion and artistic convention. Dating the precise origination of the altarpiece is somewhat elusive due to the fragmentary evidence that survives, but remaining examples indicate a natural progression from decorated gradines beginning around the twelfth century. The customary employment of veils at the back and sides of votive and high altars alike persisted into the sixteenth century in some locales, like Italy, and may explain why surfaces separate from building walls were specifically devised for altar decoration, as may the progressive dematerialization of wall mass that characterized Gothic architecture in northern Europe.8 One of the most famous and earliest surviving altarpieces, the Pala d’Oro, was constructed in the twelfth century from an earlier antependium of Byzantine provenance depicting episodes from the Life of Christ and that of Saint Mark, and was placed behind the high altar of the Venetian ducal chapel, San Marco.
Some of the earliest experimentation with painted altarpieces occurred in the prosperous Italian cities of Siena, Florence, and Venice at the cusp of the fourteenth century. The employment of monumental painted crucifixes at high altars, whether behind them or in front of them as part of rood screens, already had become widespread by the thirteenth century, and seems to have preceded the appearance of the first tavole d’altare. These representations sometimes incorporated flanking images of the Virgin and Apostles in addition to Christ’s corpus, such as the one by Cimabue in Santa Croce in Florence. Yet, the devotional icon with its attendant Byzantine artistic conventions and techniques bore an even greater impact on the nascent development of the altarpiece on the Italian peninsula from both formal and representational standpoints. The Italian tradition of painted devotional images of the Madonna and Child extends at least as far back as the early Middle Ages with the importation or replication of ‘miraculous’ images from the East, such as the Salutus Populi Romani in Rome, and was reinforced by the influx of artists from Constantinople during the Iconoclasm Controversy of the eighth and ninth centuries. Like icons, early Italian altarpieces were painted using tempera (egg yolk), which rendered vibrant hues upon their brilliant gold leaf backgrounds. The immense double-sided Maesta painted by Duccio di Buoninsegna in the early fourteenth century for the freestanding high altar of the Cathedral of Siena was dedicated to the Virgin and inaugurated with an august procession through the city, attesting to its civic role as a visual sign of Mary’s protection. Multi-paneled tavole of the fourteenth and fifteenth century often portrayed the Madonna and Child or narrative events, such as the Annunciation or Adoration of the Magi, in the central panel with titular or patron saints depicted in flanking panels that were united by an architectonic frame. However, the so-called Sacra conversazione (sacred conversation) format became the predominant representational model for late medieval Italian altarpieces, integrating an interactive company of saints, prophets, and even donors with a portrayal of the Madonna and Child. The anachronistic placement of these secondary figures in episodic depictions from the Life of the Virgin also comprised Sacra conversazione images, leaving the story-telling function of sacred art to mural cycles and ceiling frescoes.9
The Maesta by Duccio di Buoninsegna features the adoration of the enthroned Madonna and Child on the front, and episodes from the Life of Christ and the Life of the Virgin on the back. However, it would seem reasonable that the retable could be reversed so that the “back” normally would have faced out towards the celebrant and people except on special Marian feasts like the Assumption in commemoration of the cathedral’s dedication. Photos: wikimedia.org/Public Domain
In the German and Baltic lands, a highly original type of altarpiece appeared in the fourteenth century, in which side panels were attached to the central panel with hinges. Hinged panels themselves had been employed for centuries in the small ivory diptychs and triptychs carved for private devotion. According to some art historians, the winged altarpiece, or polyptych, was invented as a device for detaching images, particularly carved ones, from acts of intimate veneration such as touching or kissing.10 However, hinged wings would also have afforded the capability of concealing the full extent of carved or painted imagery during Lent or even most of the year while providing opportunities for solemn revelation during the  Eastertide or the titular feast day of the particular church or altar.11 Although in some cases the altarpiece retained the function of a reliquary, such as Tilman Riemanschneider’s Altar of the Holy Blood in Rothenburg-ob-der-Tauber (Germany), the polyptych shifted focus from a single holy figure to a narrative of Salvation history attended by a multitude of holy figures, often in the symbolic numbers of twelve or twenty-four. Thus, the comprehensive program of a polyptych served to edify the faithful in the sacramental and institutional mysteries of the Church, with the portrayal of Marian episodes such as the Assumption or Coronation frequently placed in the central panel to reinforce the Virgin’s role as the Ark of the New Covenant. Sometimes a canopied Crucifixion group crowned the entire retable. The wings, which were either carved or painted, generally portrayed episodes from the life of Christ, Mary, or a titular saint. If the exterior panels of the operable wings were carved, they were frequently finished in a monochrome wood finish that contrasted dramatically with the brilliant polychrome of the interior panels, which rendered a dazzling effect on worshippers when they were opened. Yet, by the late fifteenth century, polychromy had yielded in favor of complete monochromy, which may have reflected a growing restraint in the Church aimed at tempering the overstatement of this effect.12
When opened, the altarpiece of Saint Mary’s Church in Krakow, Poland by fifteenth-century German sculptor Veit Stoss reveals the vertical arrangement of the Dormition, Assumption, and Coronation of the Virgin with her Six Joys on the interior panels of the wings. When closed during Lent, the exterior panels show twelve scenes from the Life of Christ and the Virgin. Photos: wikimedia.org/Hans A. Rosbach/CC-BY-SA 3.0
The Ghent Altarpiece: The promise of the Annunciation, above, is fulfilled in the wedding feast of the Lamb, below. Photos: Public Domain
Painted polyptychs in the Low Countries were designed with hinged wings that could be opened for solemn occasions like their sculpted counterparts east of the Rhine. The ascendancy of a wealthy merchant class in this part of Europe meant that a great number of these altarpieces were commissioned for family chantry and guild votive chapels. Sacra conversazione depictions of Mary as the  hortus conclusus (enclosed garden) with saints and donors and episodes such as the Annunciation, Visitation, or Lamentation featured prominently in the Netherlandish repertoire, but so did the Parousia and Last Judgment.13 Jan and Hubert van Eyck’s immense fifteenth-century painted polyptych of The Adoration of the Mystic Lamb made for a chantry chapel in the present-day Cathedral of Saint Bavo in Ghent (Belgium) is considered by many art historians to be the greatest accomplishment of the early Netherlandish School, and a singular encapsulation of the Church Triumphant. When closed, its outer wings depict the Annunciation with prophets and sibyls, above, and, below, grisaille portrayals of Saint John the Baptist and Saint John the Evangelist with the chromatic figures of the patron and his wife. When opened, the polyptych reveals in a majestic orchestration of vivid colors, meticulous details, and gallant figures the fulfillment of the promise foretold to the Virgin by the Archangel on the exterior panels. Here, the Deesis presides over the unified earthly and celestial worship of the triune Godhead,  manifest in the tiered disposition of the enthroned Father, crowned by the Triregnum and resembling Christ, the radiant dove of the Holy Spirit, and the pierced Paschal Lamb. In the outermost panels at the top, a nude Adam and Eve gaze towards the Lamb upon the altar, signifying the Eucharistic sacrifice as the source of the heavenly banquet through which all mortals, beginning with the parents of mankind, might share in Christ’s triumph over death.
The great retablo in the apse, or Capilla Mayor, of the Cathedral of Toledo, Spain exemplifies the enormous scale of many Spanish altarpieces. Photo: wikimedia.org/Miguel Hermoso Cuesta
The development of the Spanish retable is fascinating for its radical departure from the two-dimensional mural tradition that had previously prevailed in the Iberian Peninsula in favor of a highly sculptural, architectonic paradigm. Whereas the first Spanish retables tended to be modest in size, later ones grew to be as tall as the church interior itself and were frequently engaged to the apse wall. The quintessential Spanish retable, standardized by the mid-fourteenth century, consisted of three symmetrically disposed parts based on contemporary Italian models: the banco, or base; the body; and the narrow frame around the body called the guadapolvos, which doubled as a dust guard. Within the retable body, a series of paintings were arrayed in vertical panes called posts or calles. The central post, which was wider and taller than the others, depicted the saint to whom the altarpiece was dedicated and served as the principal focus. Sometimes the central post was sculpted, but more often, it was painted like the flanking subordinate posts that depicted episodes from the Life of Christ or that of the titular saint. The topmost post, located above the effigy of the saint, was usually reserved for a representation of Christ crucified. A small retable may have as few as one narrative post, while larger versions may have three or more posts on either side. The banco was occupied typically by the Eucharistic image of the entombed Christ and scenes from the Passion, by images of saints, or by additional episodes from the life of the titular saint. Large retables often featured a sotabanco, which was a narrow strip below the banco that was decorated with roundels portraying the prophets. The guardapolvos was made up of slightly tilted, decoratively painted strips of wood that framed the body of the retable. Each painting in a post was outlined by a molding of gilded tracery and the whole retable often culminated in an intricately carved lantern-like canopy over the principal post, thereby helping to unify the complex organization into one monumental, glittering entity.14
In England, the pre-Reformation reredos could range in scale from a modest retable in a small church or side chapel to a massive partition in the lengthy chancel of a cathedral or abbey. The grander versions of the reredos sometimes doubled as screens separating the chancel from the retro-choir where relic shrines, chantry chapels, and tombs were often located. This was the case with the celebrated fourteenth-century Neville Screen at the high altar of Durham Cathedral that enclosed the former Shrine of Saint Cuthbert and supported painted images of the Virgin, Saint Cuthbert, and Saint Oswald, as well as a multitude of canopied statues.
Artistic Innovation and Counter-Reformation
As the preceding survey illustrates, the liturgical role of the altarpiece was not necessarily referential to the Sacrifice of the Mass in a direct or overt way with a presentation of the Crucifixion or the Last Supper as we might expect. Oftentimes, these subjects were  more likely to be found in hospital chapels or refectories than in church altarpieces. Though minimal information exists on the topic, even subjects pertaining to the titular dedication of a church, chapel, or altar do not seem to have been mandated.15 Rather, the complexities of dedication arising from the location of the altarpiece and its commissioning donors were subsumed into the burgeoning Sacra conversazione model. Another type of altarpiece that first appeared in Italy during the fifteenth century was the freestanding sculptural group. The most famous example is Michelangelo’s Pieta, which was carved around 1500 for an altar in the former church of Santa Petronilla in Rome. Statues placed on winged gradines or within retable niches, so as not to visually overpower the altar, became increasingly common during the sixteenth century.16 In general, the century witnessed a trend towards the increasing prescription of altarpiece format and content, which was rooted in the harmonics and geometric clarity established by Masaccio and Brunelleschi for the church building and its component parts as exemplified by Santo Spirito in Florence.17 The fornix motif was used to frame both painted and bas-relief retables with Titian’s Assumption at the high altar in the Franciscan church of Santa Maria Gloriosa dei Frari in Venice serving as an excellent example of this type. The uniformity of the side altar retables in Palladio’s two great Venetian churches, San Giorgio Maggiore and Il Redentore, demonstrate the fulfillment of the Brunelleschian ideal.
The Assumption by Titian is the crowned by statues of the Risen Christ, Saint Francis of Assisi, and Saint Anthony of Padua. Photo: wikimedia.org/Ricardalovesmonuments
Altarpieces generally came under fierce attack by Protestants out of their misunderstanding of Catholic tradition. While the Council of Trent called for the return to clearer forms of artistic expression, it did not set forth any particular regulations for altarpieces. Nevertheless, Carlo Borromeo, the saintly archbishop of Milan, did issue a comprehensive set of guidelines to the clergy of his archdiocese regarding the design of churches and their liturgical appointments; his insistence upon the reservation of the Sacrament in permanent tabernacles on the high altars of parish churches subordinated the visual prominence of altarpieces.18 Post-Tridentine patrons and theorists following in Borromeo’s footsteps stressed the dignifying and didactic roles of altarpieces by distinguishing, for instance, saints depicted for veneration and emulation from any other figures who might have cause to be represented.19 Despite the prescriptive attitude of the Counter-Reformation, artists responded to the challenge of elucidating the Faith and inspiring the devotion of the faithful by utilizing the full gamut of artifice to not only convey, but to amplify the sacramental mystery of the Mass. The dramatic incorporation of light became a fundamental part of altarpiece convention from the late sixteenth century onwards. In the realm of painting, artists as diametrically opposed in their methods as El Greco and Caravaggio made use of their intensely personal approaches regarding color and light to appeal to the senses and the mind. Later on, Gianlorenzo Bernini pioneered the incorporation of daylight into elaborate concetti, or ensembles of multiple media, that surpass the normal confines of the altarpiece. His design for the gilded Cathedra Petri and Holy Spirit Sunburst in the apse of Saint Peter’s Basilica is a didactic testimony to the authority of the Roman Pontiff and the legitimacy of the Catholic Church. In contrast to its grandiose scale, Bernini portrayed the spiritual ecstasy of Saint Theresa of Avila in delicately-carved marble and exuberant gilded rays with a hidden light source at the altar of an intimate chapel in the  small Roman church of Santa Maria in Vittoria. And in Sant’Andrea al Quirinale, Bernini integrated architecture, sculpture, and painting in a two-tiered concetto that seems to literally peel back the veil of mundane reality for a glimpse of the eternal. A framed painting of the martyrdom of Saint Andrew hanging above the high altar tabernacle is lit by means of a vaulted oculus, from which a cascade of gilded angels join in the celebration of both the sacred liturgy and the particular sacrifice through which Andrew imitated the superlative one of Christ. Then, in the pediment over the entrance to the apse, Bernini placed the stone effigy of the Saint being lifted into the Glory of Heaven, represented by the coffered dome and lantern that surmount the elliptical nave. Engaging the intellect and the heart, the concetto enjoins the worshipper to enter into the rapturous mystery of the Mass by offering oneself wholly to the Eucharistic Lord with the confidence of the Martyr. Thus, in its liturgical and devotional roles, the altarpiece can be both a window and a mirror, simultaneously permitting a glimpse of heavenly realities while reflecting the countenance of Christ in His saints and martyrs who united their sacrifices to His.
Concetto by Lorenzo Bernini at Sant’ Andrea al Quirinale High Altar in Rome. Photo: wikimedia.org/Tango7174
Sunburst at the Karlskirche, Vienna by Johann Fischer von Erlach. Photo: wikimedia.org/Andrzej Ostrebski