This, then, is the true knowledge of Christ, if we receive him as he is offered by the Father: namely, clothed with his gospel. For just as he has been appointed as the goal of our faith, so we cannot take the right road to him unless the gospel goes before us. And there, surely, the treasures of grace are opened to us; for if they had been closed, Christ would have benefited us little. Thus Paul yokes faith to teaching, as an inseparable companion, with these words:
You did not so learn Christ if indeed you were taught what is the truth in Christ” Ephesians 4:20-4:21
Yet I do not so restrict faith to the gospel without confessing that what sufficed for building it up had been handed down by Moses and the prophets. But because a fuller manifestation of Christ has been revealed in the gospel, Paul justly calls it the “doctrine of faith” (cf. 1 Tim. 4:6). For this reason, he says in another passage that by the coming faith the law was abolished. (Rom. 10:4; cf Gal. 3:25). He understands by this term the new and extraordinary kind of teaching by which Christ, after he became our teacher, has more clearly set forth the mercy of the Father, and has more surely testified to our salvation.
Yet it will be an easier and more suitable method if we descend by degrees from general to particular. First, we must be reminded that there is a permanent relationship between faith and the Word. He could not separate one from the other any more than we could separate the rays from the sun from which they come. For this reason, God exclaims in The Book of Isaiah:
Hear me and your soul shall live (55:3)
And John show the same wellspring of faith in these words:
These things have been written that you may believe (John 20:31)
The prophet, also, desiring to exhort the people to faith, says:
Today if you will hear his voice (Psalm 95:7; 94:8)
“To hear” is general understood as meaning to believe. In short, it is not without reason that in The Book of Isaiah, God distinguishes the children of the church from outsiders by this mark: he will teach all his children (Isa. 54:13; John 6:45) that they may learn of him. For if benefits were indiscriminately given, why would he have directed his Word to a few? To this corresponds the fact that the Evangelists commonly use the words “believers” and “disciples” as synonyms. This is is especially Luke’s usage in The Acts of the Apostles: indeed he extends this title even to a woman in Acts 9:36.
Therefore, if faith turns away even in the slightest degree from this goal toward which it should aim, it does not keep its own nature, but becomes uncertain credulity and vague error of mind. The same Word is the basis whereby faith is supported and sustained; if it turns away from the Word, it falls. Therefore, take away the Word and no faith then remain.
We are not here discussing whether a human ministry is necessary for the sowing of God’s Word, from which faith may be conceived. This we shall discuss in another place. But we say that Word itself, however it be imparted to us, is like a mirror in which faith may contemplate God. Whether, therefore, God makes use of man’s help in this or works by his own power alone, he always represents himself through his Word to those whom he wills to draw to himself. And for this reason, Paul defines faith as that obedience which is given to the gospel (Rom. 1:5), and elsewhere praises allegiance to faith in Philippians (Phil 1:3-5: cf. 1 Thess. 2:13). In understanding faith it is not merely a question of knowing that God exists, but also—and this especially–of knowing what is his will toward us. For it is not so much our concern to who he is in himself, as what he wills to be toward us.
Now, therefore, we hold faith to be a knowledge of God’s will toward us, perceived from his Word. But the foundation of this is a preconceived conviction of God’s truth. As for it’s certainty, so long as your mind is at war with itself, the Word will be of doubtful and weak authority, or rather of none. And it is not even enough to believe God is trustworthy, who can neither deceive nor lie, unless you hold to be beyond doubt that whatever proceeds from him is sacred and inviolable truth.
–John Calvin, The Institutes of the Christian Religion, vol 1. (ed. Lewis/Battles; Philadelphia, PA: Westminster, 1559), III.ii.6; pg. 548-549.