We incline to moralism by nature. In other words, not all theologies equally draw us. The theologies which draw us, as iron filings to a magnet, are the ones that have to do with self-improvement, with the righteousness of the Law. As children of Adam, we are drawn to those that say: "I stuck in my thumb and pulled out a plum, and what a good boy am I." We are not neutral toward the various theologies.
The one that is true-that Christ's death alone saves-we are hostile to, because we are children of Adam. Somebody will ask you, "Gee, don't you believe that we contributed anything to our salvation?" The Reformation answers, "Sure: sin, hostility, alienation, death, guilt." It's not the answer they are looking for, but sure we contribute all of those things and more. But we don't like that answer; we are resistant to this theology.
The reformers said that faith is of its very nature, assurance, the opposite of doubt. It rests upon the validity of the divine promise of the Gospel. Faith doubts not, though the Christian doubts often. This doubt must be reproved and combated.
But how is doubt combated? It is combated by hearing the doctrine done well. Somebody should answer back to you in terms of what the doctrine is in the promises of the Word. This is how the Spirit produces reliance and assurance. If you say, "Gee, I wonder if I'm really a Christian," and your friend asks you, "Why?" "Well, my life's just a total mess, maybe I'm not really a believer." If your friend tells you to pray harder, cry more, read the Scriptures longer, fast, and so forth-go find another friend.
Find a friend who will talk to you about Christ, what he did at the cross, the sufficiency of his death, the truth of the imputation of his righteousness to you; those are the things we need to hear. If the reformers were correct, you can relax about whether you're going to heaven, even if a lot of times you hate God. Christ died to save God-haters. And the death of Christ is greater than your hatred of God. The death of Christ is greater than your and my flabby Christian life. It is greater than that. The doctrine of justification is greater than our sin.
This doctrine is what makes Christianity Christianity. You've got to get across that the righteousness that saves isn't a change in the human heart, it's a declared sentence, "I declare you innocent." And we say, "But I'm not innocent, I'm guilty as sin!" But the judge says, "I know, but I didn't say that, I said I declared you innocent." That's what Christianity is. It's a declaration of innocence based on another's righteousness, and reckoned to you as if it were yours.