From Webster’s Dictionary:
sacred: pp of sacren, to consecrate. 1a: dedicated to or set apart for the service or worship of a diety. 1b: devoted exclusively to one service or use. 2a: worthy of religious exercises; holy. 2b: entitled to love and respect. 3: of or relating to religion; not secular or profane.
The main source of the following information is distilled from years of study, reading, and referring, to Fr. Egon Sendler’s book, The Icon: Image of the Invisible.
Ancient peoples worked out an ideal of beauty that was determined by mathematical formulas. Beauty and physical perfection was a matter of numerical relationships, including geometry. The isosceles triangle, with its perfect symmetry and firm foundation, was the basis of creative works in many cultures.
The knowledge of mathematics was applied to astronomy, music, architecture, sculpture, and art. Very often the numerical proportions were used for temples (like the Parthenon), and images of the gods (Greek and Roman statues), as ideals of beauty. This exaltation of beauty was more suitable for depicting the divine and perfect, rather than for ordinary dwellings and villages. The intention of using the proportions for worship set aside the geometry in this context as sacred.
When Christianity became prominent during the Byzantine era, these ideals were kept and adapted, but now there were new goals: to depict the human being as body AND soul, transfigured by grace. The harmony was found within the form, rather than in external numerical relationships, in modules based on nose length (a radius) and head size (concentric circles based on the radius of the nose).
In the new Christian understanding of humanity, art, and our relationship to God, the three dimensional world did not matter as much. Instead, the Byzantine Christian artist was depicting a spiritual world with no dimensions at all. In the earliest days of Christian art, communication was much more important than aesthetics; meaning more important than the exaltation of beauty. Reverence, honor, and prayer were the immediate aim of the images. However, in time icons and mosaics devoted to the worship of God became exquisitely beautiful and stylistically unique.
Cultural and historical context were mostly irrelevant, although some elements of the Byzantine culture were used as vehicles of symbolic meaning, such as items of clothing and the “band of authority” over the shoulder. This band represented the authority of the king when worn for secular business, and the authority of The Lord as truth and ruler of all, in an icon.
These elements became standardized to enable every viewer to understand and comprehend the meaning and message. Canons (laws and guidelines) were established for this purpose, and also to ensure consistency with church teaching. The “nose module” became a standard unit of measure. The canons allowed for simplifying and stylizing the figure distinctively, for a holy and liturgical purpose.
As the Byzantine Empire became a dominant power, its artistic expressions became widely known. Images became archetypes, invested with doctrinal meaning, yet still expressing an internal harmony and cohesiveness. Shapes like the balanced and pleasing isosceles triangle, and the circle became more than symbols and were integrated into the message and the composition, intrinsic to the icon. The iconographer devoted these geometric tools to the creation of works made specifically to worship God in Christian liturgy and prayer.
Why use the nose for the basic module, for the radius of a circle that all proportions are based on? The most simple reason is that the root of the nose is the center of the head circle. Ancient people also regarded it as the seat of wisdom. (This belief persists today in Hinduism and yoga: it is the site of the 6th chakra, the place of “concealed wisdom”, the place of the 3rd eye of the body, the intellect.) This widely held belief was readily adapted into the Byzantine language of the icon, and automatically understood among many cultures.