Following Constantine, Roman emperors viewed themselves as defenders of the Christian faith. That included defending Christianity from heretical diversions such as Arianism. These subsequent emperors saw themselves not only as defenders of the faith, but elected by God for Roman Rule. It was also true of Justinian. He is known for codifying and clarifying Roman Law.
The octagonal shape of San Vitale was understood to honor the martyrdom of St. Vitale. As is typical of many of the early churches and cathedrals the art that adorned its walls and ceiling were intended to convey to the common, illiterate Christian Biblical stories, interpretation, and connections with their common lives. It was not unusual to portray some contemporary political figure as participating in such stories. This teaching function of church architecture and decoration continued in San Vitale. Indeed, San Vitale is a remarkable example of the practice, displayed in the round, making it fully accessible from a single vantage point.
San Vitale Floor Plan
From early Christendom, there had been various church leaders who cautioned against taking all Biblical stories literally. That caveat continued in the mosaics of San Vitale, as described at http://employees.oneonta.edu/farberas/ARTH/arth212/san_vitale.html:
In order to “read” the mosaics and gain an understanding of the richness of their meaning, we must have an understanding of the nature of Biblical interpretation. From Early Christianity, Biblical interpretation played an integral role in religious experience. Biblical exgesis, or interpretation, traditionally defines four different levels of meaning: 1) literal or historical; 2) allegorical; 3) tropological or moral; 4) anagogical. Reading of the Bible is, thus, not limited to a record of past events, but is seen as a key to an understanding of a universal plan of history. Critical here is the relationship of the Old and New Testaments. The Old Testament is not seen as just an account of events before the time of Christ, but the events of the Old Testament are seen to “prefigure” or typologically connect to events of the New Testament. Saint Augustine of Hippo (354-430), one of the Four Church Fathers, in his City of God (XVI. 26) states that “the New Testament is hidden in the Old; the Old is clarified by the New.” Christ himself articulates this relationship when he compares Jonah’s three days spent in the belly of the sea monster to the three days he would spend in the tomb awaiting Resurection (Matt. 12:40). The story of Jonah can also be seen to link to the sacrament of Baptism. In the ritual of Baptism, the immersion in water is seen as a dying of the old self and a rebirth through Christ. In a more general sense, the story of Jonah refers to the importance of faith and prayer as the way of salvation of the “elect” from damnation. Because of his belief in God, Jonah was willing to have himself cast into the sea in order to save his shipmates. This self-sacrifice by Jonah was regularly seen as an Old Testament prefiguration of Christ’s Sacrifice on the Cross on behalf of humanity.
In your study of the mosaics, try to find the typological parallels and relationships between the different parts of the mosaic program. From the perspective of our knowledge of later Christian art, it is significant to acknowledge the absence in the mosaics of San Vitale of direct representations of New Testament images, but they are typologically alluded to in the other mosaics. Pay special attention to the importance of the figures of Christ and the Emperor Justinian. Note the number of different figures represented in the mosaic program which can be typologically related to Christ or Justinian.
San Vitale Interior
San Vitale Apse
See the above-referenced site for pictures of the church and its mosaics and for commentary. See http://smarthistory.khanacademy.org/byzantine-justinian for a video presentation and discussion of that art work.
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