“Man’s chief end is to glorify God, and to enjoy him forever,” says the Westminster Shorter Catechism. But which doctrine describes how He brings us into a relationship so that we might enjoy Him? Justification by God’s grace alone through faith alone in Christ alone.

This marvelous centerground of the biblical gospel proves the all-sufficiency of Christ the only Savior. Through it, God is glorified as utterly merciful and good, as both supremely holy and compassionate—and therefore people can find their comfort and delight in Him. Through this doctrine, even struggling believers can know a firm standing before God, gleefully knowing Him as their “Abba, Father,” confident that He is powerful to save and to keep us to the uttermost.

Comfort and Joy

To grasp this, consider how differently Roman Catholic and Reformation theologies think of our assurance of salvation. Can a believer know he is saved?

On the side of the Reformation, the Puritan Richard Sibbes argued that without such assurance, we simply cannot live Christian lives as God would have us. God, he said, wants us to be thankful, cheerful, rejoicing, and strong in faith, but we will be none of these things unless we are sure that God and Christ are ours for good.

There be many duties and dispositions that God requires which we can not be in without assurance of salvation on good grounds. What is that? God bids us be thankful in all things. How can I know that, unless I know God is mine and Christ is mine? . . . God enjoineth us to rejoice. “Rejoice, and again I say, rejoice,” Philip, iv. 4. Can a man rejoice that his name is written in heaven, and not know his name is written there? . . . Alas! how can I perform cheerful service to God, when I doubt whether he be my God and Father or no? . . . God requires a disposition in us that we should be full of encouragements, and strong in the Lord; and that we should be courageous for his cause in withstanding his enemies and our enemies. How can there be courage in resisting our corruptions, Satan’s temptations? How can there be courage in suffering persecution and crosses in the world, if there be not some particular interest we have in Christ and in God?

Yet the very confidence that Sibbes upheld as a Christian privilege was damned by Roman Catholic theology as the sin of presumption. It was precisely 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 Roman Catholic system: if we can enter heaven only because we have (by God’s enabling grace) become personally worthy of it, of course nobody 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.