It would be presumptuous to claim that we can discern precisely the approach Paul and the first missionaries would have used under direct leadership of the Spirit. But I would encourage a view of his letter to the church(es) of Rome as essentially intending to take those who already believed the Gospel, and who were therefore “saved”, back to that very Gospel, but at a more complete level of understanding.
It is clear from the explanation of his purpose in writing the letter (Romans 15:14-33) that Paul was intending to shift his center of ministry from the Eastern to the Western Mediterranean, since he had completed his work in the East. His particular vision and calling was to “preach the Gospel where Christ was not known,” and therefore following his visit to Jerusalem and a stop in Rome, he was heading for Spain (Romans 15:24-28). The clear implication of the letter is that just as other churches had an opportunity to contribute to the offering for the saints of Jerusalem, he was sure that when he visited them they would want to “assist” him on his journey to the new mission field.
Given Paul”s stated ambition to take Christ to those who had never heard, it is curious that he was “eager to preach the Gospel also to you who are at Rome” (Romans 1:15) when he came for the long overdue visit. I would argue that this did not mean that he wanted to do evangelism with them among the people of Rome (no doubt he would do that, too), but that he wanted to preach the Gospel to the church of Rome. In other words, he wanted to give the Gospel to those who had already believed the Gospel, who were “called to belong to Jesus Christ…called to be saints” (Romans 1:6-7). As he moves into the body of the letter, it becomes clear that there is far more to the gospel than is immediately apparent to a newly awakened believer. It reveals a righteousness of God that leads from faith to deeper faith (Romans 1:17).
In the chapters that follow, the Apostle unfolds with great precision the righteousness revealed in the Gospel. The exposition of this deeper understanding of the Gospel begins first with justification, then an explanation of our union with the risen Christ (often labeled sanctification), then the extraordinary privilege of adoption or sonship, and climaxing in the celebration of the predestinating purposes of God. Chapters 9-11 continue to wrestle with the Gospel and its relationship to the Jewish people. Throughout his explanation of the Gospel, Paul makes application, but it is not until ch. 12 that he begins specific teaching about the “doing” of the Christian life.
Here then is a demonstration of just how Paul worked out his constant prayer that believers would grow in the “knowledge of God”– he was eager to preach the Gospel to them. In this light, his reference to the gospel as the “power of God unto salvation for everyone who believes” (Romans 1:16) should be understood as empowering believers through every aspect of that salvation. Our more limited idea of gospel has resulted, it seems to me, in a similarly limited view of the power of God for salvation–we only think of this verse in terms of conversion, when we first believe. So understanding and continuing to believe the gospel is not only the essential task of discipleship, it provides the basis or power for attending to the doing of the Christian life–a life appropriately identified by Paul as the “obedience that comes from faith” (Romans 1:5).
To read Part 1 click: Introduction