Final answer:
Luke's main concern as a Gentile Christian was to underscore the universality and inclusiveness of Christianity, which contrasted with the exclusivity of Jewish religious practice and the hierarchical social structure of the Roman world.
Step-by-step explanation:
One of Luke's main concerns as a Gentile convert to Christianity was addressing the universality of the Christian message. Luke, like many early Christian writers, grappled with the issue of whether non-Jews could become Christians.
This concern was significant against the backdrop of a faith emerging within a predominantly Jewish context, where Jesus was initially perceived as a Jewish messiah. Furthermore, as Christianity spread, it encountered the fundamentally different values of the Roman world, such as its hierarchical social structure and legal distinctions between classes.
Luke, alongside other early Christians influenced by St. Paul's teachings, came to believe in the universal availability of salvation through Christ. This marked a departure from earlier beliefs that restricted religious participation to Jews.
Luke's writings, as seen in the Acts of the Apostles and his Gospel, emphasize the inclusive nature of Christianity and its break from traditional ethnic and social boundaries. Thus, he contributed to shaping a Christian doctrine that was open to all humanity, defying the Roman norms and culture at the time.