In spite of what the Reformers did or didn’t intend, the Protestant world in fact does now have a canon-within-the-canon — let’s call it a canonlet. It is comprised of about 3 sentences from Paul which you can recite in under thirty seconds, and these perennial struggles for “the heart of the gospel” are simply defensive actions to keep the literal meaning of other texts out of the canonlet.
“Heart of the gospel”? The instant you utter that phrase, you have a canonicity problem and you are about to whack a book or two off.
There is no meaning within the meaning. In the same way that the meaning of a poem is the poem itself, the meaning of the NT is the NT itself. It cannot be paraphrased, summarized, distilled, or focused without being falsified. When someone reads a great sonnet, and says “what does it mean?”, the only response is “here, let me read it again for you.” There is a tendency when stunned by a great work of art to want to mentally clutch it, fold it up, and take it with you; but you soon realize that in so owning it you will destroy it. So you finally understand that the only responses to art are acts: tears, laughter, your own art.
In the same way, there is a reflex to react to the gospel by trying to get your arms around it. So we write summaries and paraphrases, and kill it. The NT depicts Jesus and His news in a big sprawling mural. The great ecumenical creeds were refusals to choose one part of the mural over another (“both this and that”); the schismatic confessions (i.e. after the Schism) are the opposite of that, they are efforts to define the center of the mural (“not this but that”). The first is accepting the revelation in all its sprawling-ness, the second is actually an enthronement of human understanding.
And when the gospel got corrupted (which all churches do about every 5 minutes) the Reformers did a good thing – “here, let me read it again for you” and a bad thing – forming a canon-within-the-canon. Which was simply trying to make the mural more understandable so we can believe it better and get more “assurance”.
Hear Peter Leithart, in the spirit of the great creeds:
“… Justification by works: We are righteous before God by faith because we are united to Christ the Righteous. James says that we are “justified by works.” I don’t know precisely how to take James, but I believe we must, in faithfulness to Scripture, affirm that we are justified by works in whatever sense that James means it.” (bold mine)
Credo. I affirm whatever it means; I believe so that I can understand.