The name of Pope Sixtus III is often connected with a great building boom in Rome: Santa Sabina on the Aventine Hill was dedicated during his pontificate and he built Santa Maria Maggiore, whose dedication to Mary the Mother of God reflected his acceptance of the Ecumenical council of Ephesus, which closed in 431.
At that council, the debate over Christ's human and divine natures had turned on whether Mary could legitimately be called the "Mother of God" or only "Mother of Christ".
The council gave her the Greek title Theotokos (literally "God-bearer", or "Mother of God"), and the dedication of the large church in Rome is a response to that.
The Parting of Lot and Abraham, a Late Antique mosaic, is one of a series of scenes, probably dating to the 430s, decorating the nave wall of Santa Maria Maggiore, one of the most prominent basilican churches in Rome.
The mosaic shows the story in the biblical Book of Genesis of the parting of Abraham from his nephew, Lot, as they choose opposing paths.
Abraham chooses the road to Canaan, as God intends him to, and Lot chooses to take his followers to Sodom.
The work is a tessera mosaic, tessera describing the material making up the surface of the work.
Most tessera works during this time would be made up of small pieces of limestone or marble, cut to shape, and arranged by the artist.
The artist uses several conventions of the time.
The grouping of the characters is varied, meant to create the illusion of space.
This "shorthand" way of depicting a crowd is sometimes called a "head cluster".
There is a hieratic abandonment of consistent and realistic proportions and scale, allowing the artist to put emphasis on the characters of his choosing using attributes like size.
The main characters we are intended to focus on are made extremely clear through this method, and the picture itself becomes less illustrative and more symbolic.
Eventually this style comes to a refined maturity during the Middle Ages.
The move towards completely two-dimensional representative images has already started, and although this mosaic implements the use of lights and darks, with shadows corresponding to the figures, there is a good indication as to what direction religious art is heading.
Santa Maria Maggiore is one of only four Catholic churches that today hold the title of major basilica.
As well as this church on the summit of the Esquiline Hill, Sixtus III is said to have commissioned extensive building projects throughout the city, which are continued, after his death on August 18, 440, by his successor Pope Leo I.
Leo I begins to formulate orthodoxy and condemns Eutychianism, an extreme form of monophysitism, which holds that the human nature of Christ is absorbed by his divine nature.
In the winter, Leo I sends a letter to Valentinian III, stating "by the Holy Spirit's inspiration the emperor needs no human instruction and is incapable of doctrinal error".
