St. Athanasius in the 4th century once said this in the context of discussing the Son’s relation to the Father:
And we may perceive this at once from the illustration of the Emperor’s image. For in the image is the shape and form of the Emperor, and in the Emperor is that shape which is in the image. For the likeness of the Emperor in the image is exact; so that a person who looks at the image, sees in it the Emperor; and he again who sees the Emperor, recognises that it is he who is in the image. And from the likeness not differing, to one who after the image wished to view the Emperor, the image might say, 'I and the Emperor are one; for I am in him, and he in me; and what you see in me, that you behold in him, and what you have seen in him, that you hold in me. ’
Accordingly he who worships the image, in it worships the Emperor also; for the image is his form and appearance. Since then the Son too is the Father’s Image, it must necessarily be understood that the Godhead and propriety of the Father is the Being of the Son.
Under a similar dictum by the Cappadocian St. Basil the Great that “the honor paid to the image passes to its prototype, and he who pays homage to (
proskynon) the image, pays homage to the person whom it represents,” a legitimacy was given to the veneration of the Imperial portrait (which itself was not an uncontroversial practice).
Due to fears of possible excesses, however, measures were made beginning with Theodosius II to curb the excess of this practice of imperial image veneration. Finally, after Justinian (reigned 527-565), efforts were made to substitute the icons of Christ and of the saints for the portrait of the emperor. It is suggested that the the forms of obeisance traditionally enjoyed by official portraits of the monarch was transferred to images of Christ as sovereign and, by way of these images, to all portraits of saints. So what you have is a double influence: the practice of
honoring and commemorating the deceased via funerary portraits and that of
paying homage to the emperor via the imperial image gave way to the
commemoration and veneration of Christ, the King of Kings, and the blessed dead via their respective images. What is new is not the appearance or the increase of Christian portraits, but the development of a religious, rather than purely commemorative, veneration of Christian portraits and perhaps especially of the portrait of Christ.
This is where I should note the difference in emphasis between the East and the West on the function and nature of images.
The West has traditionally emphasized more the didactic, commemorative, and aesthetic aspects of the image. St. Augustine was a huge influence in this view: on the one hand, he was somewhat indifferent to art, arguing that images were unhistorical, juxtaposing elements which did not belong together and thus misleading the looker, and accused artists of over-literalism and anthromorphism, yet on the other hand, he had also praised beauty and the work of artisans as creations of God, and considered pictures to have at least an important illustrative value for the uneducated. More superior than pictures, however, is the word: images are viewed more as substitutes for the written text for those who cannot read.
This is partly the reason why the art of manuscript copying and illumination became a fully-developed art form in the West: the image is married to and pressed to the service of the text. It is particularly telling that by 5th century, manuscript illuminations are clearly subordinate to the written text in striking contrast to earlier images, which are largely or completely independent of text. The pictures illustrate or comment upon the written word. (Cf. the
Vatican Virgil or the
Vienna Genesis). The West took this one step further: the text itself is treated as a piece of art (cf.
historiated initials,
Hiberno-Saxon manuscript art, or Carolingian
carmina [.jpg"]figurata]("http://www.public.asu.edu/~cschleif/2 [640x480)).