Final answer:
Paul's letters are some of the oldest documents in the New Testament and were key in spreading and shaping early Christianity throughout the ancient Greco-Roman world. Manuscripts from these periods, such as codices, were essential for setting Christian doctrines.
Step-by-step explanation:
The letters written by Paul, such as those to the Ephesians, Corinthians, and Thessalonians, are among the oldest documents in the New Testament (NT). St. Paul, the Jewish leader who converted to Christianity and became its chief evangelist, played a pivotal role in shaping early Christianity. Paul's epistles addressed the Greco-Roman world and helped spread and form the Christian faith, integrating religious and cultural practices encountered in ancient Mediterranean cities. Through letters, Paul popularized the belief that Jesus's death was a divine plan to absolve human sin, a concept that generated debate among early Christians given the interpretive nature of Christ's message.
Manuscripts from these times, such as the illuminated codex created by Bishop Eadfrith, or the Gospels of Otto III, provide insight into the early depiction and spread of Christian doctrine. The codex form, used in the Glazier Codex of the 5th century, allowed discrete sections of text to be quickly found and transported by traveling priests. Both texts and their illustrations played crucial roles in establishing beliefs and standards for Christian practice.