Final answer:
St. Paul significantly impacted the early Christian church by establishing communities across the Mediterranean and converting Gentiles. He is remembered as a key apostle who spread Jesus's teachings as part of a divine message. His missionary work was pivotal in developing Christianity into a major religion within the Roman Empire.
Step-by-step explanation:
St. Paul, also known as the Apostle of the Gentiles, played a critical role in the spread of Christianity through his missionary journeys across the ancient Mediterranean world. His contributions include establishing Christian communities in key cities like Ephesus, Corinth, Thessalonica, and Rome and engaging profoundly with Greco-Roman culture. This engagement greatly influenced the development of Christian doctrine and the religion's expansion beyond Jewish communities to Gentile populations.
Paul's experience on the road to Damascus, where a vision led to his conversion from Judaism to Christianity, is seen as a pivotal moment in religious history and set the stage for his mission. He popularized the message that Jesus' crucifixion was a divine plan to absolve human sins. As a messenger sent to spread Jesus's teachings beyond Palestine, he was instrumental in opening Christianity to the Gentile world, which played a significant role in the faith's growth and eventually led to it becoming a dominant religion in the Roman Empire.