Between Two Worlds

I'm reading and greatly benefiting from J. Gresham Machen's classic book Christianity & Liberalism. If you've not yet read it, I hope the following quote whets your appetite. I love the way he defines doctrine here:

The primitive Church was concerned not merely with what Jesus had said, but also, and primarily, with what Jesus had done. The world was to be redeemed through the proclamation of an event. And with the event went the meaning of the event; and the setting forth of the event with the meaning of the event was doctrine. These two elements are always combined in the Christian message. The narration of the facts is history; the narration of the facts with the meaning of the facts is doctrine. "Suffered under Pontius Pilate, was crucified, dead and buried"--that is history. "He loved me and gave Himself for me"--that is doctrine. Such was the Christianity of the primitive Church.

To get acquainted with Machen, John Piper's biographical sermon from 1993 is the perfect place to start. I enjoyed reading it, and have also been listening to it on my iPod this week. And this site compiles a large selection of articles and information on Machen as well.