I am currently studying Romans. The questions of why Paul wrote the letter (the so-called ‘Romans Debate’) is still wide-open and scholarship is still far from generating a consensus view. There are, though a few very popular theories and one that is continually gaining steam is that the letter is audience-centered with special attention to the matter of the weak and strong (see 14-15). I think this approach has many merits as Paul (though not the founder of the church) knew a number of people there and addresses contingent issues (especially if you accept the literary stability of the whole letter).
Wedderburn has convinced many that a search for THE ONE purpose of Romans is doomed to fail. I agree. There are probably a number of reasons, but one could easily say the same about 1 Corinthians.
That Paul is expounding upon the gospel message he regularly preaches is pretty clear (especially from 3-8). The epistolary framework of the letter draws attention to some of Paul’s personal reasons (that involve himself directly): the hope to visit them and the wish to go to Spain (as well as the delivery of the collection).
A few scholars are hinting at the idea that Paul also needed to defend his apostleship (not as polemically as in 2 Corinthians, but there are some similarities). I point to Stanley Porter’s essay on ‘opponents in Rome’ in the collection Paul and his Opponents, where he explores the neglected possibility that Paul was reacting (possible pre-emptively) to opponents and had to defend his own integrity and apostleship in the process. This is not a new contribution, but Porter applies stricter methodology to the question and is more cautious. Actually, Moo’s commentary hints at Paul having to address Romans concerns based on hearing ‘rumors’ about him. For a more extreme position (that posits a more direct threat, see Stuhlmacher’s English version of his commentary, pp. 9-10; more recently Doug Campbell [Duke]). I am hesitant to jump on an oppositional bandwagon without solid evidence, but I do think Paul some of his statement’s in Romans have an unusually hostile tone (3.8). Stuhlmacher and others specifically point to 16.17: Romans 16:17, ‘I urge you, brothers and sisters, to keep an eye on those who cause dissensions and offenses, in opposition to the teaching that you have learned; avoid them. ‘ That they were aliens (foreigners) is suggested by Paul’s call to avoid them altogether. This adds a more urgent purpose to Romans, one I think needs to be more recognized.The particular contribution I want to make is this: Did Paul know of particular moral problems in the church in Rome? Specifically, did he know of sexual problems? Perhaps it may have been that he could assume they would struggle with such common issues, but there may be reason to believe he wished to present his gospel as a way of addressing these problems (in addition to other problems as well). What is the evidence? First of all, in 1.18-32 he narrates a down-spiral of humanity that traded God out for a lie and worshipped human creations. But, the results of this idolatry was sexual deviances (1.26ff.). That idolater are morally wicked was something the Romans would have agreed with. Surely even any Jew would have been able to tell the same story. But, what does Paul say to his Jewish interlocuter: if you know his will because you are instructed by the law (2.18), do you not teach against adultery and then commit it yourself (2.22)? If, in fact, that was not the case, certainly Paul’s line of argumentation would fail!
And, 6.12: ‘Let not sin reign in your mortal bodies that you obey its lusts (epithumia)’ (cf. 7.8)
Paul’s rhetoric may be simply cautionary (preventative, rather than corrective), but consider his eschatological statements: such as Romans 13.11: ‘it is now the moment for you to wake from sleep. For salvation is nearer to us now than when we first became believers.’ Is this about their moral behavior? Consider the next verses (13.12-14): ‘The night is far gone, the day is near. Let us then lay aside the works of darkness and put on the armor of light. Let us live honorably as in the day, not in reveling and drunkeness, not in debauchery and licentiousness, not in quarreling and jealousy. Rather, put on the Lord Jesus Christ, and make no provision for the flesh, to gratify its desires.’
Could such an imperatives be ‘generic paraenesis’? Consider also that in ROmans 12.1-2 (the most well-known ethical imperative in Paul) he talks about renewal of the mind for the discernment of God’s will (12.2). Here he uses the same language as in 2.18, but claiming that spiritual discernment does not come from the law, but from renewal by the Spirit. Even here he might be claiming that the law can bring knowledge of sins, but not the power to overcome Sin’s seduction. Only the gospel of Christ can destroy Sin’s power. This reading would support seeing Romans as a type of protrepsis (as Aune argues) which encourages the readers to adopt a certain course of life (or ethos).
I welcome comments on this and I hope this generates some thought on the purpose of Romans.