Faith is effectual only if one personally trusts in Christ alone for salvation. It is one thing to give an intellectual assent to a proposition but quite another to place personal trust in it. We can say that we believe in justification by faith alone and yet still think that we are going to get to heaven by our achievements, our works, or our striving. It is easy to get the doctrine of justification by faith into our heads, but it is hard to get it into the bloodstream such that we cling to Christ alone for salvation.

Faith is central to Christianity. The New Testament repeatedly calls people to believe on the Lord Jesus Christ. There is a definite body of content to be believed, which is part and parcel of our religious activity. At the time of the Reformation, the debate involved the nature of saving faith. What is saving faith? The idea of justification by faith alone suggests to many people a thinly veiled antinomianism that claims people can live any way they like so long as they believe the right things. Yet James wrote in his epistle: “What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him?…Faith by itself, if it does not have works, is dead” (2:14, 17). Luther said that the sort of faith that justifies is fides viva, a “living faith,” one that inevitably, necessarily, and immediately yields the fruit of righteousness. Justification is by faith alone, but not by a faith that is alone. A faith without any yield of righteousness is not true faith.

For the Roman Catholic Church, faith plus works equals justification; for antinomians, faith minus works equals justification; for the Protestant Reformers, faith equals justification plus works. In other words, works are the necessary fruit of true faith. Works are not factored into God’s declaration that we are just in His sight; they are not part of the grounds for God’s decision to declare us righteous.

What are the constituent elements of saving faith? The Protestant Reformers recognized that biblical faith has three essential aspects: notitia, assensus, andfiducia.

Notitia refers to the content of faith, the things we believe. There are certain things we are required to believe about Christ, namely, that He is the Son of God, that He is our Savior, that He has provided an atonement, and so on.

Assensus is the conviction that the content of our faith is true. One can know about the Christian faith and yet believe that it is not true. We might have a doubt or two mixed with our faith, but there has to be a certain level of intellectual affirmation and conviction if we are to be saved. Before anyone can really trust in Jesus Christ, he has to believe that Christ indeed is the Savior, that He is who He claimed to be. Genuine faith says that the content, the notitia, is true.

Fiducia refers to personal trust and reliance. Knowing and believing the content of the Christian faith is not enough, for even demons can do that (James 2:19). Faith is effectual only if one personally trusts in Christ alone for salvation. It is one thing to give an intellectual assent to a proposition but quite another to place personal trust in it. We can say that we believe in justification by faith alone and yet still think that we are going to get to heaven by our achievements, our works, or our striving. It is easy to get the doctrine of justification by faith into our heads, but it is hard to get it into the bloodstream such that we cling to Christ alone for salvation.

There is another element to fiducia besides trust, and that is affection. An unregenerate person will never come to Jesus, because he does not want Jesus. In his mind and heart, he is fundamentally at enmity with the things of God. As long as someone is hostile to Christ, he has no affection for Him. Satan is a case in point. Satan knows the truth, but he hates the truth. He is utterly disinclined to worship God because he has no love for God. We are like that by nature. We are dead in our sin. We walk according to the powers of this world and indulge the lusts of the flesh. Until the Holy Spirit changes us, we have hearts of stone. An unregenerate heart is without affection for Christ; it is both lifeless and loveless. The Holy Spirit changes the disposition of our hearts so that we see the sweetness of Christ and embrace Him. None of us loves Christ perfectly, but we cannot love Him at all unless the Holy Spirit changes the heart of stone and makes it a heart of flesh.

This excerpt is adapted from Everyone’s a Theologian: An Introduction to Systematic Theology by R.C. Sproul. This article is used with permission.