Historically, Protestant theologians have understood faith to contain three essential ingredients. When someone hears about the good news of Jesus Christ, first, they must understand what they’re hearing; there is a knowledge (notitia) of what and who they must believe. Second, belief consists in their assenting to (assensus) or agreeing with what they’ve heard and understood. And third, they trust (fiducia) in Christ.

From the moment Adam assented to and acted on the lie that the forbidden fruit would make him like God, unbelief became the reigning characteristic in all of God’s image bearers. Like a deep-rooted cancer, the distorting nature of disbelief marred the human race. And as humanity grew so too did the rebellion of those who came into this world suppressing the truth of God – the evidence of their unbelief seen in the foolishness of their sin (Psa. 51:5; Rom. 1:18-32).[1]

Of course, Adam was originally created to trust God, to not only believe in Him but to believe all that He promised and said. But after his fall it would take the second Adam, Jesus Christ, to reclaim and restore to humanity true belief. He alone trusted in the Father perfectly (Heb. 2:13) which is why the man Jesus Christ is “the founder and perfecter of our faith” (Heb. 12:2).  From his mother’s womb he trusted in God his Father (Psalm 22:9-10). And at his death he believed that his Father would justify him (Isa. 50:8).

Indeed, this is why unbelievers are in dire need of the Spirit of Christ, the third person of the Trinity given to God’s elect (John 6:37, 44), who alone can enable them to now rightly believe. “No one can say ‘Jesus is Lord’ except in the Holy Spirit” (1 Cor. 12:3) and it is “by grace you have been saved through faith; and this is not your own doing – it is the gift of God” (Eph. 2:8). In other words, there is a vital union with the Messiah, that Person who alone lived perfectly faithful to the Father, which is required for spiritually dead unbelievers to become truly living believers.[2]

But what is faith? We’ve seen that it was lost in Adam, and that only through the Spirit of Christ is it given to Spiritually renewed men as a gift. But what is actually happening when someone believes? Simply put, when someone exercises saving faith they are trusting in the person and work of Jesus Christ. There is an outward directed trust in Jesus. As the Puritan John Flavel once wrote, “the soul is the life of the body, faith is the life of the soul, and Christ is the life of faith.” Saving faith is trusting (in) Jesus Christ.

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