It is arguable that some of the most divisive theological problems faced by the Christian Church over the centuries have arisen from misinterpretations of the teaching of St. Paul. In fact, Paul himself complained about this latter problem in the Epistle to the Romans (3:8), and somewhat later St. Peter expressed some alarm on the matter (2 Peter 3:15-16).
In the second century the worst misunderstanding of Paul was that of Marcion. Indeed, I rarely think of Marcion without remembering what Franz Overbeck, almost a hundred years ago, said of St. Paul: "He has had only one student who understood him, Marcion--and he misunderstood him!" (Er habe nur einen Schüler gehabt, der ihn verstanden habe, Marcion--und dieser habe ihn missverstanden!')
Marcion's misinterpretation of Paul, nonetheless, forced the Catholic Christians of the second century to reflect deeply and critically about the problems of biblical interpretation and how to resolve them. Largely in reaction to Marcion they insisted that the writings of the Apostles were best understood in the local churches that the Apostles themselves had founded, not by latecomers claiming some special and rather private knowledge of the apostolic mind.
With respect to St. Paul, the Catholics of the second century observed that he conferred an inherited doctrinal authority on the ministers ordained to succeed his teaching ministry in the local churches. Paul did not tell them, "in case of a doctrinal dispute, just study my epistles very carefully, using grammars, dictionaries and the latest exegetical theories, and that should clear up the difficulty." He said, rather, "take heed to yourselves and to all the flock, among which the Holy Spirit has made you overseers (episkopous), to shepherd the church of God which He purchased with His own blood. For I know this, that after my departure savage wolves will come in among you, not sparing the flock" (Acts 20:28-30).
The second century Catholics believed they were seeing exactly that crisis of doctrine in their own lifetime, suggesting that Marcion was one of the wolves against which St. Paul had warned them (cf. Irenaeus of Lyons, Adversus Haereses 3.14.2).
I have always valued this approach to the apostolic writings. They do not come down to us as raw texts that we must somehow figure out with the proper exegetical tools, as we would other ancient texts. Faced with Homer or Vergil, just hand me the appropriate dictionary and grammar, and I can figure them out for myself. I am unable do that with Paul, however, not only because he is much harder to understand, but also because misunderstanding him poses a greater spiritual danger--perhaps even my becoming a wolf to God's flock.
This is a danger I can largely avoid, on the other hand, if only I humbly submit my mind to read Paul through the understanding of his earliest disciples and defenders, those Catholic Christians in the churches that Paul had a hand in founding.
Among these a singular weight attaches to the figure of Irenaeus of Lyons, who enjoyed the singular grace of representing Greek Asia, dominated by Ephesus and other Pauline churches. Founded by Paul, closely associated with the composition and copying of his epistles, and pastored by Timothy and others among Paul's closest associates, these churches rightly enjoyed a special authority in the determination of early Christian doctrine. Irenaeus of Lyons, for his part, is properly regarded as the spokesman for those churches. Surely, this is why we should think it presumptuous to understand Paul in any manner at variance with the way that Irenaeus understood Paul.
Irenaeus was, in fact, our first major Pauline theologian, inasmuch as he integrated the teaching of St. Paul into an original theological synthesis, 'a complete and organized image in the mind of faith' (vollständigen Abspielung in der Glaubensvernunft -- Von Balthasar). I think it important to make this point about Irenaeus, because nowadays one may read many standard historical surveys of Pauline exegesis without so much as seeing his name. The interests of these modern surveys are understandably determined by later theological controversies (Pelagianism and Protestantism, for instance), but they leave the impression (and in some instances they say explicitly!) that St. Paul was neither well understood nor really taken seriously until later centuries. This is a great and grievous mistake. Indeed, I wonder if Paul has ever since been as well understood as he was by Irenaeus and the Catholics of the second century.