What is the Gospel?

This is another post in which I'm basically just filing something for my own reference, but hopefully it can be useful for others as well.

I've had to go to the 9 Marks blog around half a dozen times in the last year trying to find these three posts from Greg Gilbert. Now I'll just do a search on my blog for "Greg Gilbert", which will make things easier.

Part 1

Part 2

Part 3

And a postscript.