Final answer:
The church's main concern in the first millennium was to establish Christian rituals and community identity, using liturgical drama and arts like the tympanum to impart Christian teachings. Baptism and communal worship were central, and pagan customs were adapted to ease the transition to Christianity.
Step-by-step explanation:
The main concern of the church during the first millennium while celebrating the liturgy was the establishment and solidification of Christian rituals and teachings in a world that was still heavily influenced by pagan traditions. Liturgical celebrations were focused on prayer, communal gatherings, and rites such as baptism, which symbolized the cleansing of the spirit and were critical for defining a communal Christian identity. Houses were transformed into house churches before proper churches were built, highlighting the need for a communal worship space.
Art played a significant role in reinforcing Christian doctrine to the largely illiterate populations of the time. Elements like the image of the Last Judgment on the tympanum of the church served to instill the principles of Christianity in the minds of the believers through what scholars call 'liturgical realism'. Additionally, the Catholic Church helped preserve theatre by introducing liturgical drama during Easter services, tying spiritual narratives to communal celebrations.
The church's approach to pagan customs was also strategic; rather than destroying them, the church would often repurpose pagan temples for Christian worship and consecrate pagan feast days to God and saints. This approach facilitated the spread of Christianity while minimizing cultural resistance.