The arts have always been an essential aspect of the language of the Christian tradition. Visual images, in particular, have provided the most immediate and direct communication of messages about Christian piety and the participation of human beings in Christian worship. The arts transcend the barriers of geography and language and, in a sense, offer an immediate form of instruction. Visual images representing the divine, scriptural and historical characters not only presented a model for the worshipper's attitudes and emotions but also provided an intensity of engagement designed to aid and improve prayer.
For illiterate people, the visual images on the walls and ceilings of churches were the primary ‘media' of instruction until at least the sixteenth century. For medieval worshippers who could not read, had scant catechetical instruction, and frequently could not hear in a large church, visual images both formed a major part of their religious initiation and informed their faith. The visual images of different historical periods record the developing nature of theology and point to changes in the artistic development of people. Many artists presented changes in theological teachings in the concrete form of their work of art.