Martin Luther certainly tried. “I was a good monk,” he wrote, “and kept my order so strictly that I could say that if ever a monk could get to heaven through monastic discipline, I should have entered in.” And yet, he found:

My conscience would not give me certainty, but I always doubted and said, “You didn’t do that right. You weren’t contrite enough. You left that out of your confession.” The more I tried to remedy an uncertain, weak and troubled conscience with human traditions, the more daily I found it more uncertain, weaker and more troubled.

According to Roman Catholicism, Luther was quite right to be unsure of heaven. Confidence of a place in heaven was considered errant presumption and was one of the charges made against Joan of Arc at her trial in 1431. There, the judges proclaimed,

This woman sins when she says she is as certain of being received into Paradise as if she were already a partaker of . . . glory, seeing that on this earthly journey no pilgrim knows if he is worthy of glory or of punishment, which the sovereign judge alone can tell.

That judgment made complete sense within the logic of the system: if we can only enter heaven because we have (by God’s enabling grace) become personally worthy of it, then of course no one can be sure. By that line of reasoning, I can only have as much confidence in heaven as I have confidence in my own sinlessness.

That was exactly why the young Martin Luther screamed with fear when as a student he was nearly struck by lightning in a thunderstorm. He was terrified of death, for without knowledge of Christ’s sufficient and gracious salvation—without knowledge of justification by faith alone—he had no hope of heaven.

And that was why his rediscovery in Scripture of justification by faith alone felt like entering paradise through open gates. It meant that, instead of all his angst and terror, he could now write:

When the devil throws our sins up to us and declares that we deserve death and hell, we ought to speak thus: “I admit that I deserve death and hell. What of it? Does this mean that I shall be sentenced to eternal damnation? By no means. For I know One who suffered and made satisfaction in my behalf. His name is Jesus Christ, the Son of God. Where he is, there I shall be also.”

And that was why the Reformation gave people such a taste for sermons and Bible reading. For, to be able to read God’s words and to see in them such good news that God saves sinners, not on the basis of how well they repent but entirely by His own grace, was like a burst of Mediterranean sunshine into the gray world of religious guilt.