The Ghent Altarpiece (also called the Adoration of the Mystic Lamb or The Lamb of God, Dutch: Het Lam Gods) is a very large and complex early 15th century Early Flemish polyptych panel painting. The altarpiece is composed of 12 panels, eight of which are hinged shutters. The wings are painted on both sides, giving two distinct views depending on whether they are open or closed. Outside of Sundays and festive holidays, the outer wings were closed and often covered with cloth. It was commissioned from Hubert van Eyck, about whom little is known. He was most likely responsible for the overall design, but died in 1426. It seems to have been principally executed and completed by his younger and better known brother Jan van Eyck between 1430 and 1432. Although there have been extensive attempts over the centuries to isolate the passages attributable to either brother, no separation has been convincingly established. Today, most accept that the work was probably designed and constructed by Hubert and that the individual panels were painted by Jan after his return from diplomatic duties in Spain.
The altarpiece was commissioned by the merchant, financier and politician, Joost Vijdt, then holding a position in Ghent similar to city mayor. It was designed for the chapel he and his wife acted as benefactors for, today's Saint Bavo Cathedral, at the time the parochial church of John the Baptist, protectorate to the city. It was officially installed on 6 May 1432 to coincide with an official ceremony for Philip the Good. It was later moved for security reasons to the principal cathedral chapel, where it remains. While indebted to the International Gothic as well as both Byzantine and Romanic traditions, the altarpiece represented a "new conception of art", in which the idealization of the medieval tradition gave way to an exacting observation of nature and unidealised human representation. A now lost inscription on the frame stated that Hubert van Eyck maior quo nemo repertus (greater than anyone) started the altarpiece, but that Jan van Eyck – calling himself arte secundus (second best in the art) – completed it in 1432. The original, very ornate carved outer frame and surround, presumably harmonizing with the painted tracery, was destroyed during the Reformation; there has been speculation that it may have included clockwork mechanisms for moving the shutters and even playing music.
The outer panels contain two vertically stacked registers (rows). The upper rows show scenes from the Annunciation of Mary. The four lower-register panels are divided into two pairs; sculptural grisaille paintings of St John the Baptist and St John the Evangelist, and on the two outer panels, donor portraits of Joost Vijdt and his wife Lysbette Borluut. The upper register of the opened view shows a Deësis of Christ the King, Virgin Mary and John the Baptist. They are flanked by images of angels singing and playing music, and, on the outermost panels, Adam and Eve. The lower register of the central panel shows the adoration of the Lamb of God, with several groups in attendance or streaming in to worship, overseen by the dove of the Holy Spirit.
Since its creation the altarpiece has been considered one of Northern European art's masterpieces and one of the world's treasures. Over the centuries the panels have come close to destruction during outbreaks of iconoclasm, or damage by fire. Some panels were sold and others looted during wars. The panels that had been taken away by the German occupying forces were returned to St. Bavo's Cathedral after World War I. In 1934 two panels, The Just Judges and Saint John the Baptist, were stolen. The panel of Saint John the Baptist was returned by the thief soon after, but the 'The Just Judges' panel is still missing. In 1945, the altarpiece was returned from Germany after spending much of World War II hidden in a salt mine, which greatly damaged the paint and varnish. The Belgian art restorer Jef Van der Veken produced a copy of the stolen panel 'The Just Judges', as part of an overall restoration effort.
- 1 Commission
- 2 Attribution
- 3 Style and technique
- 4 Open view
- 5 Closed view
- 6 Condition
- 7 Provenance
- 8 Notes and references
- 9 External links
Jodocus (known as Joos) Vijd was a wealthy merchant and came from a family that had been influential in Ghent for several generations. His father, Vijd Nikolaas (d. 1412), had been close to Louis II of Flanders. By the end of his life Jodocus had become one of the most senior and politically powerful citizens of Ghent. He was titled Seigneur of Pamele and Ledeberg, and in a difficult and rebellious political climate, became one of the Duke of Burgundy Philip the Good's most trusted local councilmen. Around 1398 Jodocus married Lysbette Borluut, who also came from a rich and established city family. The couple died childless and the endowment to the church and the commissioning of such an unprecedentedly monumental altarpiece were intended for a number of reasons, chiefly to secure a legacy. But, according to Borchert, also to "secure his position in the hereafter" and, important to such an ambitious politician, demonstrate his social prestige, revealing, Borchert believes, a desire to "show off and ... outstrip by far all other endowments to St John's, if not each and every other church and monastery in Ghent."
Ghent prospered through the early 1400s, and a number of local councilors sought to establish a sense of independence from Burgundian rule. Philip was experiencing financial difficulty in the early 1430s, and made strong demands on the city to provide revenue, a burden many of city councilors felt was unreasonable and that they could ill afford, financially or politically. The situation was tense, and because there was division within the council over the burden, this led to a mistrust that meant council membership was dangerous and precarious. During a power play in 1432 a number of councilors were murdered, seemingly for their loyalty to Philip. The tension came to a head in a 1433 revolt which ended with the beheading of the councilors who had acted as ringleaders. Throughout all this Vijd stayed loyal to Philip. His position as warden at St. John the Baptist's church (now Saint Bavo Cathedral) reflects this; the church was favoured by the Burgundians for official ceremonies held in Ghent. On the day of the altarpiece's consecration, 6 May 1432, Philip's and Isabella of Portugal's son was baptised there, a strong indicator of Vijd's status at the time.
Vijd, as warden (kerkmeester) of St. John's, between 1410 and 1420 not only financed the construction of the principal chapel's bay, but endowed a new chapel off the choir, which took his family name and was regularly to hold masses in his and his ancestors' memory. It was for this new chapel that he commissioned Hubert van Eyck to create an unusually large and complex polyptych altarpiece. He was recorded as donor on an inscription on the original, now lost, frame. The chapel was dedicated to St. John the Baptist, whose traditional attribute is the Lamb of God, a symbol of Christ.
The attribution of the painting to the van Eyck brothers is broadly established by the small amount of surviving documentary evidence attached to the commission, and from the signature and dating on a reverse frame by Jan van Eyck, who seems to minimize his contribution in favor of his brother, who was dead 6 years by the time of work's completion in 1432. A less explicit indicator is their seeming portraits as the third and fourth horseman in the Just Judges panel. Ramsay Homa notes lettering in the central panel of the lower register that might be read as an early formation of what was to become Jan's well known signature, built around various formations of "ALS IK KAN" (As I Can), a pun on his full name. The lettering is found on the headdress of one of the prophets standing at the back of the grouping. It seems to be in a Hebrew script that may translate, inelegantly, into French as Le chapeau ... orne de trois lettres herbraiques formant le mot Saboth, or more likely as "Yod, Feh, Aleph", which when transliterated represents Jan's initials, JvE.
Since the 19th century, art historians have debated which passages were executed by the little-known and obscure Hubert and which by his brother Jan, famous across Europe from the early 1430s. In the 17th and 18th centuries, before his reassessment, it was often assumed that Jan had found a number of random panels left behind after Hubert's death and assembled them into the current format. This view has been discounted since the early 19th century, on the basis of the obvious overall design of the work, although there are obvious stylistic differences between many passages. Today it is generally accepted that the majority were completed by Jan, from an overall design by Hubert, who may also have constructed parts of the frames. A number of difficulties present themselves, not least that there is no surviving work confidently attributed to Hubert, and it is thus impossible to detect his style. Instead, art historians have resorted to comparing individual passages to known works by Jan, looking for stylistic differences that might indicate the work of another hand. Advances in Dendrochronology have for example established that parts of the wing panels were felled around 1421. Allowing a seasoning time of at least 10 years, we must assume a completion date well after Hubert's death in 1426, thus ruling out his hand from large portions of the wings.
Style and technique
Although Jan was skilled as a miniaturist, and there is much evidence of that ability in the details of the Ghent Altarpiece, the polyptych differs in a number of significant aspects to the other paintings generally attributed to him, not least in its scale. In addition, it is the only work thought to be of his hand that was intended for public, rather than private, worship and display. Van Eyck pays as much attention to the beauty of earthly things as to the religious themes. The clothes and jewels, the fountain, nature surrounding the scene, the churches and landscape in the background – are all painted with remarkable detail. The landscape is rich with vegetation, which is observed with an almost scientific accuracy, and much of it non-European.
Lighting plays a central role and is one of the major innovations of the polyptych. The panels are infused with complex light effects and subtle plays of shadow, the rendering of which was achieved through a new technique of handling oil paint as well as the use of transparent glazes. The figures are mostly cast with short, diagonal shadows which serve to, in the words of art historian Till-Holger Borchert, "not only heighten their spatial presence, but also tell us that the primary light source is located beyond the picture itself." In the Annunciation scene of the outer panels, shadows are depicted in a manner that implies that they emanate from the daylight within the chapel in which they are housed.
A further innovation can be found in the detailing of surface textures, especially reflections and refractions. This is best seen in details such as the effect of the fall of light on the armor in the Knights of Christ panel, and the ripple of the water in the Fountain of life in the Adoration of the Mystic Lamb. Yet although the work contains many individual innovations, it did not emerge spontaneously, but is rather part of a long tradition of oil painting and altarpiece design of the southern Netherlands. A great number of these works were destroyed during the iconoclasm of the mid 16th century, a period in which the Ghent Altarpiece was twice nearly destroyed; on 19 August 1566, and again in 1576 when a special guard was put on the work to protect it from rioters. The scale of destruction in these waves was such that the Ghent historian Marcus Van Vaenewijk (1516–69) recorded that in the summer of 1566 the burning pyres on which the works were thrown could be seen from 10 miles away. Because of this, art historian Susie Nash points out that the Ghent work seems so unusual in part because it was one of the few major examples to survive wholly intact.
The altarpiece was opened on feast days, when the richness, colour and complexity of inner view was intended to contrast with the relative austerity of the outer panels. As viewed when open, the panels are organised along two registers (levels), and contain depictions of hundreds of figures. The upper level consists of seven monumental panels, each almost six feet high, and includes a large central image of Christ flanked by frames showing Mary (left) and John the Baptist (right), which contain over twenty inscriptions each referring to the figures in the central Deësis panels. These panels are flanked by two pairs of images on the folding wings of the altarpiece. The pair of images closest to the Deësis show singers in heaven, while the outermost pair show Adam and Eve, naked save for strategically placed fig leaves. The lower register has a panoramic landscape stretching continuously across five panels. While the individual panels of the upper tier clearly contain separate – albeit paired – pictorial spaces, the lower tier is presented as a unified Mise en scène. Of the 12 individual panels, eight have paintings on their reverse visible when the altarpiece is closed.
The three central upper panels show a Deësis of monumental and enthroned figures, each with a halo. They are the Virgin Mary to the left, John the Baptist to the right, and a central figure whose identity is unclear – he is either God or Christ – leading to much debate among scholars. Theories include that he is Christ in Majesty, dressed as in a priest's vestments, God the Father, or the Holy Trinity amalgamated into a single person – Elisabeth Dhanens believes that the fact he wears a triple tiara lends credence to this long held view.
The central figure faces the viewer with his hand raised in blessing, against a panel filled with inscriptions and symbols. Greek inscriptions decorated with pearls are on the hem of his robe or mantle, which, taken from Revelation, read REX REGUM ET DOMINUS DOMINANTIUM ("King of Kings, and Lord of Lords"). The golden brocade on the throne features pelicans and vine, probable references to the blood spilled during the Crucifixion of Jesus; pelicans were at the time believed to spill their own blood to feed their young, while the vines refer to sacramental wine, the eucharistic symbol of Christ's blood. A crown is at his feet, and on either side the step is lined with two levels of text. The left hand upper line reads VITA SINE MORTE IN CAPITE ("Life without death on his head"), that on the right LUVENTUS SINE SENECTUTE IN FRONTE ("Youth without age on his forehead"). These are placed above - on the left and right respectively - the words GAUDIUM SINE MERORE A DEXTRIS ("Joy without sorrow on his right side") and SECURITAS SINE TIMORE A SINISTRIS ("Safety without fear on his left side"). The crown serves as a transition to the Lamb panel directly below and perhaps serves to symbolize that those figures in the lower register panels who represent humanity flock to pay homage to God.
To the left Mary reads from a girdle book draped with a green cloth. The book is an unusual attribute for Mary, according to Pächt, who writes that van Eyck may have based the figure on Robert Campin's Virgin Annunicate. She is wearing a crown adorned with flowers and stars, and according to Dhanens is dressed as a bride. The inscription on the arched throne above reads: "She is more beautiful than the sun and the army of the stars; compared to the light she is superior. She is truly the reflection of eternal light and a spotless mirror of God". Like Mary, John the Baptist holds a holy book - likewise an unusual attribute, and one of 18 books in the set of panels. He wears a green mantle over a cilice of camel-hair. He looks towards the Almighty in the center panel, also with his hand raised in blessing, uttering the words most typically associated with him, ECCE AGNUS DEI ("Behold the Lamb of God").
It is often assumed that given the foreshortening seen in the representation of God the Father, the artist was familiar with the either of the Italian painters Donatello or Masaccio. However Susie Nash suggests van Eyck was already leading toward this development, and it was something he was "perfectly capable of producing without such models", and believes the technique represents "a shared interest [rather than] a case of influence."
The two musical panels are commonly known by variants of the titles Singing Angels and Music-making Angels, and are both 161 cm x 69.3 cm. Each features a choir; on the left angels gather behind a wooden carved music stand positioned on a swivel, to the right a group with stringed instruments gather around a pipe organ, played by a seated angel, shown full-length. The presence of the two groups on either side of the Deësis reflects a by then well-established motif in representations of the heavens opening; that of musical accompaniment provided by celestial beings. As was common in the Low Countries in the 15th century, the angels are dressed in liturgical robes, a custom that migrated from Latin liturgical drama to the art of the period.
The angels are attendant to the King of Kings, that is, to God the father in the central Deësis panel. This idea reflects a motif popular in the hagiography of the early 15th century. They are presented without many of the attributes usually associated with depictions of angels in northern art of the time. Most obviously, they do not have wings, while their faces are unidealised and show a number of different individual expressions. Music historian Stanley Boorman notes that their depiction contains many earthly qualities, writing that "the naturalism is so seductive that the viewer is tempted to consider the scenes as depictions of contemporary church music." Yet he concludes that the inscriptions "reinstalls them in the heavenly sphere". In both panels the angels stand on maiolica tiles decorated with the IHS Christogram, representations of the lamb and other images. The frame of the left hand panel is inscribed with the words, MELOS DEO LAUS ("Music in Praise of God"), the frame of the right with LAUDATE EUM IN CORDIS ET ORGANO ("Praise him with stringed instruments and organs"). A number of art historians have defined the figures as angels based on their positioning and role within the overall context of the registers. They are sexless and possess cherub faces, which contrast with the realistic depictions of the other full-sized non-divine females in the work; Eve in the same register and Lysbette Borluut in the outer panels. The angels are dressed in elaborately brocaded ecclesiastical copes or chasubles, mostly painted in reds and greens. Their robes indicate that they are intended as representative of the celebration of mass before the altar in the lower central panel.
The left-hand group shows eight fair haired angels wearing crowns and gathered in front of a music stand singing, although none of them looks towards the score on the stand. As in a number of the other panels, here van Eyck used the device of the open mouth to give a sense of life and motion to his figures. Borchert writes that the emphasis on the open mouths is "specifically motivated by the desire to characterize the angel's facial expressions according to the various ranges of polyphonic singing. To that end the position of the angel's tongues are carefully registered, as are that of their teeth." Art historian Elisabeth Dhanens notes that "One can easily see by their singing who is the soprano, who is the alto, who is the tenor and who is the bass". The panel deviates from common performance practice, however, with its wave-like order in body height, and the orientation of all eight faces in different directions. A number of scholars have written on their physiognomy. Their cherub faces and long, open, curly hair are similar but also show a clear intention by the artist to establish individual traits. Four angels are shown frowning, and three of these have narrowed eyelids which give the appearance that they are peering, a trait also seen in some of the apostles in the "Adoration of the Lamb" register. Pächt sees this as highly unusual in Jan van Eyck's presentation of figures and speculates that their expressions are remnants of Hubert's initial design.
In the right-hand panel, the only angel fully visible is the organist around whose instrument the others gather. Although a larger group is suggested, only another four angel's faces can be seen in the closely cropped huddle. These other angels carry stringed instruments, including a small harp and a type of viol. The instruments are shown in remarkable detail. The organ at which Saint Cecilia sits is detailed with such precision that in places its metal surfaces show reflections of light. Until the Trecento, when the idea of orchestration was introduced, music playing angels were typically winged, depicted holding stringed or wind instruments as they hovered "on the wing" around on the edges of images of saints and deities. In French illuminated manuscripts of the first two decades of the 1400s, winged angels often seemingly floated on the margins of the page, as illustrations to the accompanying text. Art historian Otto Pächt notes however, that here the angels are not expected to simultaneously "fly, sing and play", and that their "music-making" seems to be conducted on a "more professional level ... [more] in accordance with all the rules of church music."
Adam and Eve
The two outer panels show near life-sized nudes of Adam and Eve standing in stone niches. They are the earliest treatment in art of the human nude with Early Netherlandish naturalism, and are almost exactly contemporary with the equally ground-breaking pair in Masaccio's Expulsion from the Garden of Eden in Florence of about 1425. The Ghent figures face inwards towards the angels and the Deësis, separating them. They self-consciously attempt to cover their nakedness with a fig leaf as in the Genesis account, indicating that they are depicted as after the fall of man. Eve holds a fruit in her raised right hand; not the traditional apple but a small citrus, most probably a citron. Erwin Panofsky drew particular attention to this element, and described it as emblematic of the "disguised" symbolism he saw running through the work as a whole. Both figures' eyes are downcast and they appear to have forlorn expressions. Their apparent sadness has led many art historians to wonder about van Eyck's intention in this portrayal. Some have questioned if they are ashamed of their committal of original sin, or dismayed at the world they now look upon.
The realism with which Jan approached his figures is especially evident in these two panels. The depiction of Eve exemplifies the Late Gothic ideal for the female figure, as developed in International Gothic art around the start of the century, and pioneered in nude form by the Limbourg brothers, especially their Adam and Eve in the Très Riches Heures du Duc de Berry. Comparing the Limbourg's Eve to a classical female nude, Kenneth Clark observed that "her pelvis is wider, her chest narrower, her waist higher; above all there is the prominence given to her stomach". Clark describes the Ghent Eve as "a proof of how minutely 'realistic' a great artist may be in the rendering of details, and yet subordinate the whole to an ideal form. Hers is the supreme example of the bulb-like body. The weight-bearing leg is concealed, and the body is so contrived that on one side is the long curve of the stomach, on the other downward sweep of the thigh, uninterrupted by any articulation of bone or muscle."
The precision and detail with which their nakedness is recorded offended many over the years. During a visit to the cathedral in 1781, Joseph II of Bohemia and Hungary found them so disagreeable that he demanded they be removed. The couple's nakedness further offended 19th century sensibilities, when their presence in a church came to be considered unacceptable. The panels were replaced by reproductions in which the figures were dressed in skin cloth; these are still on display in the Saint Bavo Cathedral. In comparison to contemporary depictions of Adam and Eve, this version is very spare and omits the usual motifs associated with the theme; there is no serpent, tree or any trace of the garden of Eden normally found in contemporary paintings. In contrast to the other panels in the register, Adam and Eve are positioned near the edge of each panel, and neither is entirely within the border of their setting. Most obviously Adam's foot appears to protrude out of the niche and frame and into real space. More subtly, Eve's arm, shoulder and hip appear to extend beyond her architectural setting. These elements give the panel a three-dimensional aspect. The trompe-l'œil become more pronounced when the wings are turned slightly inwards, an especially interesting fact when it is considered that the polyptych was wider than the original chapel it was executed for and could never be opened fully.
Above Adam is a grisaille depiction of Abel making a sacrifice of the first lamb of his flock to God and Cain presenting part of his crops as a farmer to the Lord, and above Eve is one showing the murder of Abel by his brother Cain with an ass's jawbone because, according to the Bible, Cain was jealous of the Lord's acceptance of Abel's offering over Cain's. Van Eyck gives the figures a statuesque look, adding depth to the picture.
Both Adam and Eve are depicted with a navel. Paintings of naked human beings without navels look unnatural and given the level of detail in the panels this was probably a deliberate choice and not oversight.
A continuous panoramic landscape unifies the five panels of the lower register, with the center panel showing the adoration of the Lamb of God (Agnus Dei) in a scene derived from the Gospel of John. Groupings of people stream in to worship him; four groupings are shown congregating at each corner of the central panel, while another four arrive in the two pairs of outer panels – the Warriors of Christ and Just Judges on the left-hand side, and the holy hermits and pilgrims on the right. Of the eight groupings only one consists of females. The groupings are segregated by their relationship to the old and new testaments, with those from the older books positioned to the left of the altar.
Among the pilgrims on the outer right-hand panel is a giant Saint Christopher, patron saint of travelers. At the rear of the hermits on the inner right-hand panel is Mary Magdalene, carrying ungutents. The four wings are over ten centimeters longer than the central panel, a fact that has puzzled art historians over the centuries. Theories as to why this may be so range from speculation that they were unfinished works by Hubert that Jan completed and assembled, to that the central panel was originally larger and at some stage cut down. This latter theory has been discounted more recently after technical examination.
Adoration of the Mystic Lamb
Measuring 134.3 x 237.5 cm, the center panel has as its centerpiece an altar on which the Lamb of God is positioned, standing in a verdant meadow, while the foreground shows a fountain. Five distinct groups of figures surround altar and fountain. In the mid-ground two further groups figures are seen gathering; the dove of the Holy Spirit is above. The meadow is framed by trees and bushes; with the spires of Jerusalem visible in the background. Dhanens says the panel shows "a magnificent display of unequaled color, a rich panorama of late medieval art and the contemporary world-view." In 1495, Hieronymus Münzer described the piece as the eight beatitudes, saying of "And all of this is painted with such wondrous ingenuity and skill, that you would suppose this to be not merely a painting but the whole art of painting." Dhanens speculates one of the groupings may have been on the lost predella. The iconography, as suggested by the groupings of the figures, appears to follow the liturgy of All Saints' Day.
Lamb of God
The lamb stands on an altar, facing the viewer and is surrounded by 14 angels arranged in a circle, some holding symbols of Christ's Passion, and two swing censers. The lamb has a wound on its breast from which blood gushes into a golden chalice, yet it shows no outward expression of pain, a reference to Christ's sacrifice. The angels have vivid multicolored wings and hold instruments of Christ's passion, including the cross and the crown of thorns. The antependium on the upper portion of the front of the altar is inscribed with the words taken from John 1:29; ECCE AGNUS DEI QUI TOLLIT PECCATA MUNDI ("Behold the Lamb of God who takes away the sins of the world"). The lappets bear the phrases IHESUS VIA ("Jesus the Way") and VERITAS VITA ("the Truth, the Life"). Although the centerpiece of the panel, the lamb is placed in the mid-ground, making the viewer look beyond the foreground figures to see the central motif of the work.
The dove of the Holy Spirit hovers low in the sky directly above the lamb, surrounded by concentric semicircles of white and yellow hues of varying luminosity, the outermost of which resembles nimbus clouds. Thin golden beams emanating from the dove resemble those surrounding the head of the lamb, as well as those of the three figures in the Deësis panels in the upper register. The rays seem to have been painted by van Eyck over the finished landscape, and serve to illuminate the scene in a celestial, supernatural light. This is especially true with the light falling on the saints positioned directly in front of the altar. The light does not give reflection or throw shadow, and has traditionally been read by art historians as representing the New Jerusalem of Revelations which in 21:23, had "no need of the sun, neither of the moon, to shine in it; for the glory of God did Lighten it". This illumination contrasts with the natural and directional lighting of the four upper interior wings, and of each of the outer wings. It has been interpreted as a device to emphasize the presence of the divine and accentuate the paradise of the central landscape. The dove as the Holy Spirit, and the lamb as Jesus, are positioned on the same axis as that of God The Father in the panel directly above; a reference to the Holy Trinity.
Fountain of life
In the center foreground the fountain of life is connected to a small river, its bed covered with jewels. In the distance, the minutely detailed cityscape again recalls the New Jerusalem. Nature is depicted with an attention to detail not seen before in Northern European art, and far supersedes what went before. Although the numerous species of plants are depicted in miniature, they are recognizable and known species, both those native to Northern Europe and those native to the Mediterranean, and are reproduced with a high level of botanical accuracy. Similarly, the clouds and rock formations in the distance contain degrees of verisimilitude that evince studied observation. The landscape in the distance contains representations of actual churches, while the depiction of the mountains beyond contain the first known example in art of aerial perspective. Yet the panel does not strive for exact realism; the sum of the forensically detailed natural elements, in combination with the apparition of the Holy Spirit and extended beams of light, serve to create a wholly individual and uniquely creative interpretation of a classic biblical scene. The fountain's rim shows the carved inscription, HIC EST FONS AQUE VITE PROCENDENS DE SEDE DEI + AGNI ("This is the fountain of the water of life, proceeding out of the throne of God and of the Lamb"), symbolizing the fountain of life is "watered by the blood of the Lamb"  A center column rises out of the fountain topped by an angel with bronze dragons below; jets of water stream from the dragons into the fountain. The vertical axis from the fountain of water to the altar with the blood show the testimonies of spirit as cited in John, 5:97. Like the altar above, ringed by angels, the fountain is surrounded by figures, these arranged in distinct groupings.
Prophets, Apostles, and Church figures
The semi-circle of figures to the left and right of the fountain consist of various biblical, pagan, and church figures, some crowded around the fountain in what Pächt describes as two "processions of figures [that] have crowded to a halt". To the left are representatives of figures from Judaism and prophets who have foretold the coming of Christ; to the right representatives from the Church. The figures directly to the left of the fountain represent witnesses from the Old Testament; dressed in pink robes, kneeling, reading aloud from open copies of the Bible, facing the mid-ground with backs turned to the viewer. A larger group of pagan philosophers and writers stand behind them. These men seem have traveled from all over the world, given the Oriental faces of some, and their different styles of headdress. The figure in white, holding a laurel wreath, is generally accepted to be Virgil, who is said to have predicted the coming of the Saviour. Isaiah stands to his side holding a twig, a symbol of his own prophesy of Christ as recorded in Isaiah 11:1. Opposite on the right, kneel the twelve apostles from the New Testament before a group of male saints. These, dressed in red vestments symbolizing martyrs, are the Popes and other clergy representing the church hierarchy. A number are recognizable, including Saint Stephen who carries the rocks with which he was stoned. Three popes in the foreground represent the Western Schism—a dispute that festered and lingered in Ghent—and are identifiable as Martin V, Gregory VII and Antipope Alexander V. Dhanens suggest the positioning of popes standing beside antipope shows "an atmosphere of reconciliation".
Confessors and martyrs
In the mid-ground, to the left and right of the altar, are two more groups of figures: the male martyrs (all visible are clergy) and female martyrs. Identifiable biblical figures carry palms. These enter the pictorial space as though through a path in the foliage, males standing to the left, women to the right. The female martyrs, sometimes known as the holy virgins, are gathered by an abundant meadow, a symbol of fertility. A number are identified by their attributes: in front St. Agnes carries a lamb, St. Barbara a tower, Saint Catherine of Alexandria is finely dressed, and St. Dorothy carries flowers; further back St. Ursula carries an arrow. On their heads they wear flowered crowns. The men, on the left, consist of confessors, popes, cardinals, abbots and monks who are dressed in blue.
Just Judges and the Knights of Christ
Winged panels to the left of the "Adoration of the Mystic Lamb" show groups of approaching knights and judges. Their biblical source can be identified from inscriptions on the panel frames. The far left hand panels contain lettering reading "CHRISTI MILITES" (Warriors of Christ), and the inside left panel "IUSTI IUDICES" (Righteous (or Just) Judges). The presence of the Judges, none of whom were canonised saints, is an anomaly which art historians have long sought to explain. The most likely explanation is that they refer to Jodocus Vijd's position as an alderman of Ghent.
The "Just Judges" is thought to contain portraits of both Jan and Hubert as the third and fourth Judges on horseback. The evidence for this is the similarity of one of the figures to Jan's London Portrait of a Man of 1433, which is generally thought to be a self-portrait. The second, closer, figure is thought to be Hubert, because of facial similarity to Jan. Although the judge in the Ghent panel appears to be younger than the sitter in the London painting, they wear similar chaperons with the cornette tightly bound around the bourrelet. The judges in the Ghent panel became the basis for a number of later portraits of the brothers, including that of Dominicus Lampsonius.
The altarpiece measures 375 cm x 260 cm with the shutters closed. The upper panels contain separate lunettes showing prophets and Sibyls looking down on an annunciation scene; the lower tier shows the donors on the far left and right panels flanked by saints. The exterior panels are executed with reserve and sparseness in comparison to the often fantastical colour and abundance of the scenes on the interior which they conceal. Their pictorial spaces are confined and, especially in the upper register, cramp the figures. The settings are earthly, pared down and relatively simple. Yet there is the same striking use of illusionism which also characterises the inner panels; this is especially true of the faux stone grisaille statues representing the saints. Lighting is used to great effect to create the impression of depth; van Eyck handles the fall of light and casting of shadow to make the viewer feel as if the pictorial space is influenced or lit by light entering from the chapel in which he stands.
The figures in the lunettes refer to prophecies of the coming of Christ. The far left lunette shows the prophet Zechariah and the far right one shows Micah. The two much taller inner shutters show the Erythraean Sibyl (on the left) and the Cumaean Sibyl on the right. Each panel includes a text inscribed on a floating ribbon or "banderole", while the identities of the figures are carved on the lower border of each panel. Zechariah's text, taken fron Zechariah 9:9, reads EXAULT SATIS FILIA SYON JUBILA ECCE REX TUUS VENTI ("Rejoice greatly, O daughter of Zion ... behold, your king comes"), while the Erythraean Sibyl's words are NIL MORTALE SONAS AFFLATA ES NUMINE CELSO ("Sounding nothing mortal you are inspired by power from on high"). To the right the Cumaean Sibyl's reads REX ALTISSIMUS ADVENIET PER SECULA FUTURUS SCILICET IN CARNE ("The Highest King shall come and shall be in the flesh through the ages").
Zechariah and Micah look down on the fulfillment of their prophecies contained in the banderoles floating behind them. The Erythraean Sibyl is shown observing, while the Cumaean Sibyl, wearing a green dress with thick fur sleeves, gazes down at Mary, her hand held in empathy over her own womb. Micah's lunette employs one of the first instances of an illusionistic motif best known from Petrus Christus's Portrait of a Carthusian (c.1446), wherein the sense of the boundary between the painting, frame and viewer's space becomes blurred. In this instance, the prophet knowingly places his hand outwards on the lower border of the frame.
In October 1428 Jan did accompany a Burgundian embassy, this time for the hand of Isabella, eldest daughter of John I of Portugal (reg 1385–1433). After a storm forced them to spend four weeks in England, the Burgundians arrived in Lisbon in December. In January they met the King in the castle of Aviz, and van Eyck painted the Infanta's portrait, probably in two versions to accompany the two separate groups who left by sea and by land on 12 February to report the terms to the Duke. The portraits are untraced, but one is preserved in a drawing (Germany, priv. col., see Sterling, fig.), which reveals that Jan used the princess's Portuguese dress for the Erythrean sibyl on the Ghent Altarpiece.
In the mid 20th century, art historian Volker Herzner noted the facial similarity between the Cumaean Sibyl and Philip's wife Isabella of Portugal, especially as she is portrayed in van Eyck's now lost betrothal portrait of 1428–1429. Herzner speculated that the text in the banderole in the sibyl's panel has a double meaning, referring not only to the coming of Christ, but also to the 1432 birth of Philip's first son and heir to survive infancy. Others reject this idea, given the high rates of infant mortality at the time, and the connotations of bad luck usually associated with acclaiming a son before he is born.
The two outer panels of the middle register show the Annunciation to Mary, with the Archangel Gabriel on the left and the Virgin Mary on the right. Both are dressed in white robes, and occupy what appear to be the opposite ends of the same room. The figures of Mary and Gabriel are disproportionately large in relation to the scale of the rooms they occupy. Art historians agree that this follows the conventions of both the International Gothic and late Byzantine traditions of the icon by showing saints, especially Mary, in a much larger scale than their surroundings. In this instance their size is probably a device to convey the idea that they are heavenly apparitions who have come momentarily before the donors who are in the lower register. Van Eyck used this conceit most dramatically in his Madonna in the Church, (c. 1438–40) which is likely a panel from a dismantled diptych.
Gabriel has blond hair and multicoloured wings. His right hand is raised and in his left he holds lilies, traditionally found in paintings of the annunciation as symbols of Mary's virginity. His words to Mary are written alongside him in Latin: AVE GRACIA PLENA D(OMI)N(U)S TECU(M) ("Hail who art full of grace, the Lord is with you"). The horizontal inscription extends out the panel and halfway across the neighbouring image. As in van Eyck's Washington Annunciation of c. 1434–6, the letters of Mary's reply are inscribed in reverse and upside-down; as if for God to read from heaven, or for the holy spirit, as represented by the dove, to read as he hovers directly above her. She answers ECCE ANCILLAM D(OMI)NI ("Behold the handmaiden of the Lord").
Gabriel and Mary's panels are separated by two much narrower images showing unoccupied domestic interior scenes. The back wall in the left-hand image has a window opening onto a view of street and city square, while that in the right-hand image has a niche. Some art historians have attempted to associate this street with an actual location in Ghent, but it is generally accepted that it is not modeled on any specific place. The sparseness of these narrow panels seem anomalous in the overall context of the altarpiece; a number of art historians have suggested that they were compromises worked out by Jan as he struggled to accommodate his design within the original framework set out by Hubert.
Penny Jolly suggests that in the mid to late 1420s he may have traveled to Italy at the behest of the Duke of Burgundy where, in Florence, he probably saw an iconic 14th century annunciation, and perhaps visited more contemporary annunciation scenes. These Florentine annunciations had a number of iconographic similarities found in the Ghent panels: Gabriel's multi-colored wings, the upside down writing, the treatment of light beams, and the separation between angel and virgin by a thin architectural feature. Some of these elements, particularly the spatial separation between the two figures, can be found in Lorenzo Monaco's Bartolini Salimbeni Annunciation in Santa Trinita, finished before his death in 1424, and one that Jan may have seen. In Monaco's painting the angel and Mary are separated by two small spaces, one external and one internal, similar to the city-scape and domestic lavabo panels in the Ghent annunciation.
The style of the furnishings of the room and the modernity of the town visible through the arched window set the panels in a contemporary 15th century setting. The interiors have been cited as one of the first representations of medieval "bourgeois domestic culture". Borchert sees this familiar setting as a device to allow 15th century viewers to connect with the panel and so reinforce the conceit that the two saints are apparitions occupying the same space and time as the donor or observer. Yet a number of features in the interior suggest that it is not a secular domestic space, most obviously the cool and austere surfaces, the domed windows and stone columns.
The four panels are most obviously connected by the similar floor tiling and single vanishing point. Shadows falling on the tiling at the lower right hand corner of each panel can only have been cast by the moulding on the frames, that is from an area outside of the pictorial space.
The figures in the four panels of the lower register are all positioned within uniform niches. The outer panels show the donors Joost Vijdt and his wife Lysbette Borluut. The inner panels contain grisaille paintings of Saint John the Baptist and Saint John the Evangelist. The use of grisaille gives the illusion of sculpture, and implies that these are cult representations of the two saints before which the donors kneel, gazing into the distance with their hands clasped together, in rapt veneration. As with the most of the other panels on both the inner and outer views, they are lit from the right. Shadows thrown by the figures are used to establish depth, and bring realism to both the faux statues and painted niches.
Saints and donors
Each saint stands on a stone plinth inscribed with his name. John the Baptist, the son of the priest Zechariah (not to be confused with the prophet of the same name shown on the upper register), holds a lamb in his left arm and is turned towards Joost Vijdt. His right hand is raised and his finger extended to point towards the lamb, a gesture that implies that he is reciting the Agnus Dei. John the Evangelist holds a chalice, a reference to the early medieval tradition that he had ability with cures; he could drink poison from a cup without ill effects.
The donors are painted life size, and thus to a much larger scale than the saints; this is most noticeable in the relative sizes of their heads and hands. Their bright and warmly colored clothes contrast sharply with the grey of the lifeless saints. Van Eyck brings a high degree of realism to his portrayal of the Vijdts; his study of the ailing couple in old age is unflinching and far from flattering. Details that reveal their aging include Joost's watering eyes, wrinkled hands, warts, bald head and stubble streaked with gray. The folds of both figures' skin are meticulously detailed, as are their protruding veins and fingernails. The portraits are generally thought to be among the final panels completed in the altarpiece, and thus are typically dated to 1431 or to the early months of 1432.
The first significant restoration was carried out in 1550 by the painters Lancelot Blondeel and Jan van Scorel, following the earlier and poorly executed cleaning by Jan van Scorel, that led to damage to the predella. The 1550 undertaking was performed with a care and reverence that a contemporary account writes of "such love that they kissed that skilful work in art in many places". The predella was destroyed by fire in the 16th century. Comprising a strip of small square panels and executed in water based paints, it showed hell or limbo with Christ arriving to redeem those about to be saved. During the Protestant Reformation the piece was moved out of the chapel to prevent damage in the Beeldenstorm, first to the attic and later to the town hall, where it remained for two decades.
A program of restoration at the Museum of Fine Arts, Ghent began in October 2012, and is projected to last five years. Only the panels being worked on are in the museum at any one time, with the others remaining on display in the cathedral. At the museum the public can see the work in progress from behind a glass screen. The last previous major restoration was conducted in 1950–51, after damage sustained during its stay in the Austrian mines during WWII, during which newly developed techniques, such as x-ray, were applied to the panels.
The altarpiece has been moved several times over the centuries. Art historian Noah Charney describes the altarpiece as one of the more coveted and desired pieces of art, the victim of 13 crimes since its installation, and seven thefts. After the French Revolution the altarpiece was among a number of art works plundered in today's Belgium and taken to Paris where they were exhibited at the Louvre. It was returned to Ghent in 1815 after the French defeat at the Battle of Waterloo. The painting's wings (not including the Adam and Eve panels) were pawned in 1815 by the Diocese of Ghent for the equivalent of £240. When the diocese failed to redeem them, they were sold by the dealer Nieuwenhuys in 1816 to the English collector Edward Solly for £4,000. The pieces spent some months in London, during which time the new owner unsuccessfully sought a buyer. They were later bought by the King of Prussia for £16,000, a huge price at the time, and for many decades they were exhibited in the Gemäldegalerie, Berlin. The panels still in Ghent were damaged by fire in 1822, and the separately hinged Adam and Eve panels sent to a museum in Brussels.
During World War I, other panels were taken from the cathedral by German forces. Under the terms of the Treaty of Versailles and its subsequent reparations transfers, Germany returned all the panels, and, in 1920, after a century of separation, all the panels were again in Ghent. In 1934, the panels of 'The Just Judges' and 'Saint John the Baptist', were stolen. The panel of 'Saint John the Baptist' was returned by the thief as a goodwill gesture, but the 'The Just Judges' panel is still missing. The Germans "bitterly resented the loss of the panels" and, at the start of another invasion by Germany in 1940, a decision was made in Belgium to send the altarpiece to the Vatican to keep it safe. The painting was in France, en route to the Vatican, when Italy declared war as an Axis power alongside Germany. The painting was stored in a museum in Pau, and French, Belgian and German military representatives signed an agreement which required the consent of all three before the masterpiece could be moved. In 1942, Adolf Hitler ordered the painting to be seized and brought to Germany to be stored in the Schloss Neuschwanstein castle in Bavaria. After Allied air raids made the castle too dangerous for the painting, it was stored in the Altaussee salt mines. Belgian and French authorities protested against the seizing of the painting, and the head of the German army's Art Protection Unit was dismissed after he disagreed with the seizure.
The altarpiece was recovered by the Americans after the war and returned to Belgium in a ceremony presided over by Belgian royalty at the Royal Palace of Brussels, where the 17 panels were displayed for the press. No French officials were invited, as the Vichy French had allowed the Germans to remove the painting.
Notes and references
- Burroughs (1933), 184
- Gombrich, E.H., The Story of Art, pages 236–9. Phaidon, 1995. ISBN 0-7148-3355-X
- Burroughs, 184–193
- Website with scanned reconstructions of the frame from Lotte Brand Philip's book, The Ghent Altarpiece (Princeton, 1971), which originated some of these ideas.
- Kurtz (2004), 24
- Borchert (2008), 31
- Borchert (2008), 32–33
- Hagen et al., 37
- Borchert (2008), 32
- Borchert (2008), 17
- "The Infant Saint John with the Lamb". National Gallery, London. Retrieved 17 November 2012.
- Homa (1974), 327
- Pächt, 214
- Nash (2008), 13
- Harbison (Reaktion), 194
- Borchert (2011), 22–23
- Harbison (1995), 81
- Borchert (2011), 24
- Nash (2008), 11-12
- Nash (2008), 14
- Harbison (1995), 836
- Pächt (1999), 124
- A device later borrowed by Rogier van der Weyden for his The Braque Triptych
- Borchert (2011), 19
- Lane (1984), 109
- Dhanens (1980), 106
- Charney (2010), 31
- Ridderbos et all (2004), 48
- Pächt (1994), 129-130
- Dhanens (1980), 106-108
- Dhanens (1980), 108
- Nash (2008), 30
- Pächt (1999), 124, 151-152
- McNamee, 268-274
- For example in the then popular "Golden Legend" manuscript.
- Boorman (1983), 30
- Boorman (1983), 31
- Borchert (2011), 31–2, see also Golaqki-Voutrira (1998), 65–74
- Pächt (1999), 152
- Pächt (1999), 151
- Duby, George,A History of Private Life, Vol 2 Revelations of the Medieval World, 1988 (English translation), p.582, Belknap Press, Harvard University
- Snyder, 511
- Clark, 310
- Clark, 311
- Hagen et al., 39
- Borchert (2008), 28
- Charney (2010), 64
- Harbison (1995), 83
- Hagen et al. (2003), 38
- Pächt (1999), 212
- Dhanens (1980), 97
- Pächt (1999), 12
- Dhanens (1980), 104
- Dhanens (1980), 103
- Ridderbos at al (2004), 47
- This portion of the panel was restored following damage suffered in an 1822 fire; however the restoration was not complete and some of the passages were abandoned mid-way. The most startling result of this is that a portion of an underdrawing of the lamb was left exposed, leading to it now appearing to have four ears. See Pächt, (1999), 123
- Pächt (1999), 138
- Borchert (2011), 23
- Borchert (2008), 21
- Ridderbos et al. (2004), 53
- Charney (2010), 23
- Borchert (2008), 29
- Pächt (1999), 126
- Dhanens (1980), 100
- Dhanens (1980), 100.103
- Ridderbos et al., 54
- Campbell (1998), 216
- Bourchert (2008), 93–95
- Borchert (2011), 25
- Virgil, Aeneid, 6:50 "nec mortale sonans, adflata est numine"
- Ridderbos et al. (2004), 43
- Jolly (1998), 376
- The Oxford Art Online – Jan van Eyck
- The portrait is known today from a 17th-century pencil copy. Other art historians have suggested that the Virgin in van Eyk's Washington Annunciation bears Isabella's face. See Wolff, Hand (1987), 81
- Ridderbos at al (2004), 58–9
- Harbison (2012), p. 99
- Ridderbos et al. (2004), 19 & 77
- Jolly (1998), 375
- Harbison (1995), 82
- Borchert (2011), 27
- Jolly (1998), 374
- Pächt (1999), 13
- Pächt (1999), 169
- Jolly (1998), 392
- These panels resemble passages from van Eyck's c 1436 Virgin and Child with Canon van der Paele, and the manner of depicting the aged in such a way is characteristic of a number of works produced by the workshop after his death. See Borchert (2011), 30
- Meiss, Millard. "'Nicholas Albergati' and the Chronology of Jan van Eyck's Portraits". The Burlington Magazine, Volume 94, No. 590, May, 1952. 137
- Pächt (1999), 120
- Nash (2008), 67
- Pächt (1999), 132
- Charney (2010), 15
- Museum for Fine arts Ghent
- Charney (2010), x
- Charney (2010), 1
- Deam (1998), 3
- Reitlinger (1961), 130
- Kurtz, Michael J. (2006). America and the return of Nazi contraband. Cambridge University Press. p. 25.
- Kurtz (2006), 132
- Ainsworth, Maryan Wynn. From Van Eyck to Bruegel: Early Netherlandish painting in the Metropolitan Museum of Art. New York: Metropolitan Museum of Art, 1999. ISBN 0-300-08609-1
- Borchert, Till-Holger. Van Eyck. London: Taschen, 2008. ISBN 3-8228-5687-8
- Borchert, Till-Holger. Van Eych to Durer: The Influence of Early Netherlandish painting on European Art, 1430–1530. London: Thames & Hudson, 2011. ISBN 978-0-500-23883-7
- Boorman, Stanley (ed). Studies in the Performance of Late Medieval Music. Cambridge: Cambridge University Press, 1983. ISBN 0-521-08831-3
- Burroughs, Bryson. "A Diptych by Hubert van Eyck". The Metropolitan Museum of Art Bulletin, Volume 28, No. 11, Pt 1, November 1933.
- Campbell, Lorne. The Fifteenth-Century Netherlandish Paintings. London, National Gallery. New Haven: Yale University Press, 1998. ISBN 0-300-07701-7
- Charney, Noah. Stealing the Mystic Lamb. New York: PublicAffairs. 2010. ISBN 1-58648-800-7
- Deam, Lisa. "Flemish versus Netherlandish: A Discourse of Nationalism". Renaissance Quarterly, Volume 51, No. 1, Spring 1998.
- Dhanens, Elisabeth. Hubert and Jan van Eyck. New York: Tabard Press. 1980. ISBN 0-914427-00-8
- Hammer, Karl. Secret of the sacred panel. London: Stacey international, 2010. ISBN 978-1-906768-45-4
- Harbison, Craig. "The Art of the Northern Renaissance". London: Laurence King Publishing, 1995. ISBN 1-78067-027-0
- Homa, Ramsay. "Jan van Eyck and the Ghent Altar-Piece". The Burlington Magazine, volume 116, No. 855, June 1974.
- Honour, Hugh; Fleming, John. "A World History of Art". London: Laurence King Publishing, 2005. ISBN 1-85669-451-8
- Jolly, Penny. "Jan van Eyck's Italian Pilgrimage: A Miraculous Florentine Annunciation and the Ghent Altarpiece". Zeitschrift für Kunstgeschichte. 61. Bd., H. 3, 1998
- Kurtz, Michael. America and the return of Nazi contraband. Cambridge: Cambridge University Press, 2004. ISBN 978-0-521-84982-1.
- Lane, Barbara. The Altar and the Altarpiece, Sacramental Themes in Early Netherlandish Painting. London: Harper & Row, 1984. ISBN 0-06-430133-8
- McNamee, W.B. "The Origin of the Vested Angel as a Eucharistic Symbol in Flemish Painting". The Art Bulletin, Volume 53, No. 3, September 1972.
- Nash, Susie. Northern Renaissance art. Oxford: Oxford University Press, 2008. ISBN 0-19-284269-2
- The Oxford Art Online – Jan van Eyck // 
- Pächt, Otto. Van Eyck and the Founders of Early Netherlandish Painting. 1999. London: Harvey Miller Publishers. ISBN 1-872501-28-1
- Reitlinger, Gerald. The Economics of Taste, Vol I: The Rise and Fall of Picture Prices 1760–1960. London: Barrie and Rockliffe, 1961.
- Ridderbos, Bernhard; van Buren, Anne; van Veen, Henk. Early Netherlandish paintings: Rediscovery, Reception and Research. Amsterdam: Amsterdam University Press, 2004. ISBN 90-5356-614-7
- Schmidt, Peter. Het Lam Gods. Leuven: Uitgeverij Davidsfonds, 2005. ISBN 90-77942-03-3
- Seidel, Linda. "The Value of Verisimilitude in the Art of Jan van Eyck". Yale French Studies: Special Issue: "Contexts: Style and Values in Medieval Art and Literature", 1991. 25–43
- Snyder, James. "Jan van Eyck and Adam's Apple". The Art Bulletin, Volume 58, No. 4, December 1976.
- Wolff, Martha; Hand, John Oliver. Early Netherlandish painting. National Gallery of Art Washington; Oxford University Press, 1987. ISBN 0-521-34016-0
- van Elslande, Rudy. De geschiedenis van de Vyt-Borluutfundatie en het Lam Gods, in: Ghendtsche Tydinghen, 14de jg., 1985, nr.6, blz. 342-348; Ibidem, 15de jg., 1986, nrs 1-6, blz. 56-58, 108-111, 168-171, 230-233, 282-284, 329-332; Ibidem, 16de jg., 1987, nrs.1-6, blz. 25-29, 102-105, 143-148, 201-204, 269-272, 335-349; Ibidem, 18de jg., 1989, nrs. 1-2, blz. 53-55, 95-99.
|Wikimedia Commons has media related to Ghent Altarpiece.|
- Closer to Van Eyck: Rediscovering the Ghent Altarpiece Royal Institute for Cultural Heritage (Belgium). High resolution macrophotography, infrared reflectography and X-radiography of the Ghent Altarpiece.
- Website of the Saint Bavo Cathedral in Ghent (Belgium)
- The theft of the Just Judges
- An alternative interpretation of the iconography of the Ghent Altarpiece[dead link]
-  Hitler's Hunt for the Holy Grail and the Ghent Altarpiece