Open, the Ghent Altarpiece's twelve panels build one of the most ambitious theological programs in Northern European painting. Its top register shows God the Father enthroned in majesty between the Virgin Mary and John the Baptist, flanked by singing and instrument playing angels and, at the outer edges, Adam and Eve painted with a startling, almost uncomfortable physical realism for the period. Below, the central Adoration of the Mystic Lamb gathers popes, bishops, martyrs, virgins, prophets and knights from every era of sacred history into one continuous landscape, all converging on a small lamb standing on an altar, blood flowing visibly from its side into a chalice, a direct visualisation of Christ as the sacrificial Lamb of God from the Book of Revelation.
The rhymed quatrain discovered on the frame in 1823 names Hubert van Eyck as the artist who began the work and calls him greater even than his brother, then names Jan van Eyck as the one who completed it after Hubert's death in 1426 and dated the finished altarpiece to 6 May 1432. That inscription is also part of why the painting matters technically: the van Eyck brothers are traditionally credited, on the strength of works exactly like this one, with perfecting oil paint as a medium capable of the luminous, jewel like colour and fine detail the Ghent Altarpiece still displays five centuries later, at a moment when most European panel painting still relied on tempera. Few single works are credited with both a major theological statement and a technical revolution in how paint itself was used.