The heart of the gospel

Bob at In the Clearing is thinking about J.I. Packer and the true heart of the gospel:

I looking for the gold, the real value, the deep things beneath the chaff of the contemporary. In my experience, preachers tend to talk a lot about God's ability to take care of us, to see to our circumstances. Ah, yes, "circumstances." God will help you through them. God is greater than them. Are you dealing with money issues, relationship issues, these issues, those issues? Give 'em to God. He's good, strong, and loving. He'll take care of you. That's the adumbrated contemporary gospel. And you know what? It's not the gospel of the New Testament.

And what is the heart of the gospel? How about the propitiation of sins?