Justification remains a controversial doctrine. New Testament scholars are reexamining Paul's teaching. Lutherans and Roman Catholics have produced aJoint Declarationon the topic. The excerpts from John Calvin's writings below give us a glimpse into the Reformation doctrine of justification by faith.

Calvin taught clearly about justification by faith and the assurance that this can bring us. But what did he mean by justification?

We explain justification simply as the acceptance with which God receives us into his favour as righteous men. And we say that it consists in the remission of sins and the imputation of Christ's righteousness. (Institutes 3:11:2)

Justification means that God accepts us as righteous, but this does not mean that we can just continue to sin. Justification always goes hand in hand with sanctification.

As Christ cannot be torn into parts, so these two which we perceive in him together and conjointly are inseparable—namely, righteousness and sanctification. Whomever, therefore, God receives into grace, on them he at the same time bestows the Spirit of adoption, by whose power he remakes them to his own image. (Institutes 3:11:6)
Therefore Christ justifies no one whom he does not at the same time sanctify. (Institutes 3:16:1)

The reason that they always go together is that we have them both by being united to Christ.

Now, both repentance and forgiveness of sins—that is, newness of life and free reconciliation—are conferred on us by Christ, and both are attained by us through faith. (Institutes 3:3:1)
Our righteousness is not in us but in Christ, … we possess it only because we are partakers in Christ. (Institutes 3:11:23)
We say that faith justifies, not because it merits righteousness for us by its own worth, but because it is an instrument whereby we obtain free the righteousness of Christ. (Institutes 3:18:8)

It is only by faith that we are united to Christ and are justified in him.

The power of justifying, which faith possesses, does not lie in any worth of works. Our justification rests on God's mercy alone and Christ's merit, and faith, when it lays hold of justification, is said to justify. (Institutes 3:18:8)

It is only by faith — but this faith is not alone.

It is therefore faith alone which justifies, and yet the faith which justifies is not alone: just as it is the heat alone of the sun which warms the earth, and yet in the sun it is not alone, because it is constantly conjoined with light. (Acts of the Council of Trent: with the Antidote, 6th Session, can. 11)
We confess with Paul that no other faith justifies "but faith working through love" [Gal. 5:6]. (Institutes 3:11:20)
We dream neither of a faith devoid of good works nor of a justification that stands without them. This alone is of importance: having admitted that faith and good works must cleave together, we still lodge justification in faith, not in works. (Institutes 3:16:1)

So what does Calvin mean by "faith"? He gives a clear definition.

Now we shall possess a right definition of faith if we call it a firm and certain knowledge of God's benevolence toward us, founded upon the truth of the freely given promise in Christ, both revealed to our minds and sealed upon our hearts through the Holy Spirit. (Institutes 3:2:7)

Faith rests on God's promise of salvation in Christ, so faith includes within it the assurance or confidence of salvation.

They are ignorant of the whole nature of faith who mingle doubt with it. (Acts of the Council of Trent: with the Antidote, 6th Session, ch. 9)

But while faith brings confidence, we as believers struggle constantly with unbelief.

Surely, while we teach that faith ought to be certain and assured, we cannot imagine any certainty that is not tinged with doubt, or any assurance that is not assailed by some anxiety. On the other hand, we say that believers are in perpetual conflict with their own unbelief. Far, indeed, are we from putting their consciences in any peaceful repose, undisturbed by any tumult at all. (Institutes 3:2:17)

The object of faith is God's promises in Christ.

It is [God's] will that we be content with his promises, and not inquire elsewhere whether he will be disposed to hear us. (Institutes 3:24:5)

When we have faith in Christ God accepts not just us as individuals but also our good works, imperfect though they are.

The disciples of Christ love him with sincere and earnest affection of heart, and according to the measure of their love keep his commandments. But how small is this compared with that strict perfection in which there is no deficiency? (Acts of the Council of Trent: with the Antidote, 6th Session, ch. 11)
Therefore, as we ourselves, when we have been engrafted in Christ, are righteous in God's sight because our iniquities are covered by Christ's sinlessness, so our works are righteous and are thus regarded because whatever fault is otherwise in them is buried in Christ's purity, and is not charged to our account. (Institutes 3:17:10)
We … remarkably cheer and comfort the hearts of believers by our teaching, when we tell them that they please God in their works and are without doubt acceptable to him. (Institutes 3:15:7)
He who is justified will not forget that a reward is laid up for him, but be incited by it as the best stimulus to well-doing. And yet he will not look to this alone. (Acts of the Council of Trent: with the Antidote, 6th Session, can. 31)

Tony Lane is professor of historical theology at London School of Theology.

Institutes excerpts are from Calvin: Institutes of the Christian Religion, translated by Ford Lewis Battles (Westminster John Knox Press, 1960)