This interchange created an awkward moment for me. Clearly this student had been formed by the dominant church tradition on the interpretation of Paul, a venerable heritage that goes back through Calvin and Luther even to Augustine. However, like most interpreters of Paul I don't think that's the answer to the question. Even more important, I think the question is more important than most of our attempts to answer it. I try to avoid undermining students in front of their peers, but this student's direct answer required something. I think I said, "That's one of the most popular answers to this question. At the same time, we have an entire semester to pursue the question itself. Let's see how things go."
If any passage in the Pauline letters "gives away" Paul's gospel, it's probably 1 Thessalonians 1:9-10. Paul's gospel was his proclamation of what God has done in Christ. First Thessalonians is probably the oldest of Paul's letters available to us, and the first half of the book is devoted to reminiscences of Paul's first encounters in Thessalonica. In other words, in 1 Thessalonians we have our earliest record of what Paul's ministry was about, albeit through Paul's skilled rhetorical handiwork.
Paul reminds the Thessalonians of the reputation they earned during his visit: "how you turned to God from idols, to serve a living and true God, and to wait for his Son from heaven, whom he raised from the dead -- Jesus, who rescues us from the wrath that is coming" (1:9b-10).
This looks very much like a summary of Paul's core message. It is essentially a story, not a doctrinal formulation, and it features four parts.
- The God of Israel has broken into history, inviting Gentiles into God's people. (Paul is clearly talking about Gentiles, who turn from idols to serve a living and true God. That's how a Jew would have referred to Gentile converts.)
- God's intervention comes in the person of Jesus Christ.
- God has raised God's Son from the dead.
- Those who await Christ's return will be delivered from end-time calamity. (Whether "the wrath that is coming" refers to end-time chaos, a final judgment, or both, I'm not sure.)
Why do I suggest this proclamation is close to Paul's gospel, rather than the familiar "justification by grace through faith"? All of Paul's letters feature the same gospel story, but only some emphasize salvation by grace through faith. Among the seven "undisputed" letters of Paul, those all scholars affirm as coming from the apostle himself, only two really articulate the "justification by grace through faith" formula. Both of them, Galatians and Romans, address the problem of how Jews and Gentiles could live together in the church. (Though probably not written by Paul, Ephesians features the same concerns: salvation [rather than justification] by grace through faith, combined with the reconciliation of Jews and Gentiles.)
It seems that "justification by grace through faith" emerged not out of Paul's core gospel proclamation but from a pastoral concern: how Jews and Gentiles could live together as one body. That's not to deny justification's importance. It's critical to both theology and piety. Sometimes pastoral crises, even conflicts, generate the most important insights.
Just the same, Paul's gospel proclamation was probably a story about Jesus Christ and how God has broken into history to create a renewed people. Paul may have told the story in diverse ways in diverse contexts. Surely he applied it with flexibility. But his core message was a story about God and Jesus Christ.