Mutual Identities. The Construction of the Figure of the Pope and the Emperor in the Carolingian Age: Historical Perspectives.

Since late antiquity, the Pope's image took on symbolic elements and functions of imperial dignity, a process accentuated in the course of the 8th century until it became central in the Carolingian age when the rebirth of the imperial title in the West imposed a redefinition of roles.
In this path of identity building, a primary function rested on the visual component through rites and liturgies and above all through the figurative arts which crystallized the image of the pope making it "eternal".
Particularly significant in this perspective is the Lateran Triclinium which, through its mosaic decoration, became a manifest image of Roman caesaropapism and for this reason was restored, reconstructed and re-evaluated several time, so much so that it is still with us today albeit in a completely upset context.
The iconographic programme of the mosaic of the Triclinium also harmonizes with what we know about the monumental aula concilii, the main apse of which reaffirmed the theme of papal power derived from Christ through Peter, a value attributed to the building as a whole which was repeatedly emphasized during the Middle Ages, until the time of Boniface VIII.