Tim Gallant is a Reformed pastor. His blog is called Rabbi Saul. This post (from his blog: 3-10-04) shows how close Reformed and Catholic thought is in this respect (as in many respects). I've slightly abridged it for presentation here (I'm trying to keep the posts as short as I can). The last two paragraphs are from one of Tim's subsequent comments.
I am becoming more and more convinced that for Paul, the gospel is ecclesiologically shaped. This is not to say that it is not soteriological (i.e. that it does not concern "salvation"), but rather the opposite, that in his view, salvation itself is an ecclesiological issue.
I have often expressed the complaint that 99% of Protestant (and even Reformed) discussions of salvation could dispense altogether with the church. Take, for example, the classic ordo salutis: election, effectual calling, justification, sanctification, glorification (or similar variations). The way this is usually articulated, the Church need not exist. Yet we think we understand the gospel when we can articulate such an ordo (and in particular, the "justification" section, which is narrowly focused upon faith and imputation).
Frankly, I don't think the author of Galatians would recognize us. Even more fundamentally, I don't think that we recognize him.
Paul is writing to a church that is being called upon to become circumcised and follow the Mosaic calendar (see 4.10). The so-called Judaizers are demanding this in order to recognize full covenantal membership of Gentiles. Paul introduces the Peter story as within this same category of thought - a story that is merely about table fellowship.
There is no evidence that Peter ever uttered a word to the Gentiles of Antioch that they needed to earn their salvation by keeping the Mosaic law. In fact, there is no evidence that the Judaizers in Galatia ever said so either.
But Paul treats both Peter's actions and the Judaizers' teaching as an assault upon the gospel. Frankly, I don't think that in parallel circumstances, we would - or do. Segregated communion in the American south has much more to do with Galatians than arguments over whether Norman Shepherd or Tom Wright has quite articulated the doctrine of justification properly. Reformed church A barring members of Reformed church B from the table has much more to do with Galatians than arguments over whether or not obedience is a "necessary condition" for salvation. Barring our children from the table until they can work their way over the hurdle of physiological development has far more to do with Galatians than whether we've quite managed properly to correlate the eschatological judgment according to works with the doctrine of sola fide. (If in no other way, yet here we may say that the Eastern Orthodox are being eminently more faithful with the gospel than are the hyper-orthodox-Westminster-is-inerrant-theologically-straitjacketed-defenders-of-"the-faith"-who-won't-share-a-table-with-anyone-outside-the-.00001%-margin-of-error-difference-from-themselves.)
And I suggest that the reason we usually fail to recognize this is precisely because, for us, the Church really doesn't matter. Salvation happens in your heart, in your heart, in your heart. The only Church that matters is the one you can't see anyway, because it's invisible. (Which really is no church at all. An invisible church without sacraments, without ministers, a church that you join in your heart is absolutely meaningless. The invisible church will do you as much good as an invisible, bodiless, incorporeal Christ. The bonus is that if you are satisfied with an invisible church, you will probably settle for a completely invisible heaven while you are tortured in hell in a merely visible and tangible state of existence, which we all know doesn't matter.)
Paul says that salvation happens at the font (Gal 3.27). It happens at the table. Those excluded from the table are delivered over to Satan (1 Cor 5) . . . "One baptism" is at the very heart of the Pauline gospel.
. . . we will never understand Pauline soteriology until we are mastered by his view of the Church. The Gospels preach "the gospel" without ever entering into technical theological discussions. They preach the gospel by presenting Jesus as proclaiming good news to the poor, as drawing the rejected and the outcasts around Himself and forming them into a new community. They preach the gospel by proclaiming the kingdom of God, a kingdom which is founded upon His death . . .
[W]e won't be able to understand the issue until we recognize that "salvation" is not merely an individual experience between the believer and God. The fall entails a loss of humanity, particularly in terms of community. Salvation entails the creation of a new humanity. Connection to Christ occurs in the form of membership in the body of Christ. Baptism (=being clothed with Christ) is baptism "into one body" (1 Cor 12.12-13).
IMHO, the Bible is relatively unconcerned regarding the direct question, "Can salvation be lost?" This is because the Bible's predominant understanding of salvation is shaped differently from our own. I am more concerned for us to reshape ourselves to the biblical pattern than to answer the questions that primarily arise from the wrong starting point to begin with. It seems to me that there are better, more biblical routes, to dealing with questions of assurance than getting into abstract discussions regarding whether "real" salvation can be lost. I will say, readily, that the number whom God has predestined to eternal life is fixed and unchangeable. I will say that there really are such people as hypocrites. But for the moment, I'll stop.