We’ve never had more access to knowledge than we do today. Your smartphone is a reference librarian bringing the world to your fingertips. Curious about the hypostatic union? Just google it. Looking for a definition of penal substitutionary atonement? Ask Siri (it works; I tried).

All this information can be overwhelming, and explains why someone might ask, “How much must I know to be saved?” or, more precisely, “What exactly must I know to be sure I have eternal life?” Clearly, we must know something. As John Murray rightly taught, “There is a knowledge that is indispensable to faith.” But what knowledge? And how much of it is required?

Bad Question?

Should we even be asking such a question? As in all of life, motives matter. Your goal should not be to affirm the least amount of doctrinal truth you need to get to heaven. Instead, aim to maximize the amount of truth you know. “Give me understanding,” David prayed, “that I may keep your law and observe it with my whole heart” (Ps. 119:34).

Asking how little we have to know to be a Christian is a bit like asking how much we’re allowed to sin and still be a Christian. A person aspiring toward a tolerable level of rebellion is not a true believer. Likewise, someone hoping to believe as little as possible probably doesn’t know the Lord.

J. Gresham Machen said he often got asked how little of the gospel one needed to accept to be saved. He refused to answer this question—though for a slightly different reason. He insisted the question is unanswerable:

Who can presume to say for certain what is the condition of another man’s soul; who can presume to say whether the other man’s attitude toward Christ, which he can express but badly in words, is an attitude of saving faith or not?

Machen pinpointed a perennial pastoral problem. A member of my church has Down syndrome. Years ago, the church welcomed him into fellowship. He sings as joyfully as anyone. He participates in Sunday school with fervor. He speaks as well as he can of Jesus in his heart, though he struggles to articulate the gospel in an understandable way. One can’t be sure exactly how much he comprehends. I presume Machen had cases like this in mind when he wrote, “This is one of the things which must surely be left to God.”

Worthy Question

As difficult or even impossible as the question may be to answer, faithfulness demands we try. Jesus said entrance into the kingdom of God requires we repent and believe (Mark 1:15). It is not, therefore, unwise to ponder what, in fact, we must believe. And though this belief is more than intellectual adherence to sound doctrine, it is not less.

Though [saving] belief is more than intellectual adherence to sound doctrine, it is not less.

We’re on shaky, unstable ground if we try to slice and dice the precise amount of doctrine required to enter heaven. But the Bible is not silent about what one must believe to be a Christian. And what one must believe will surely affect how we speak to others as we endeavor to be Christ’s ambassadors (2 Cor. 5:20).

Biblical Answer

In Romans 9 Paul laid down the gauntlet on behalf of God’s sovereignty. Salvation is in the hands of the Lord. He redeems as he sees fit, according to his will and with the ultimate end of bringing glory to his great name. The kindness of God that leads us to repentance (Rom. 2:4) is undeserved and unasked for until God’s Spirit changes our desires. Our salvation doesn’t rest on our wisdom, works, or will; we are redeemed according to his sovereign plan and purpose. Our faith does not save us; God does.

And yet, God doesn’t save us apart from repentance and faith. Thus, in Romans 10, Paul lays down the gauntlet on the side of human responsibility. Whom does God save? Paul’s answer is clear:

If you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. (Rom. 10:9)

You must know who Jesus is and what he’s done. He’s more than a rabbi, a carpenter, or a truth-seeker. He is the Lord, with supreme authority over all things, including you. When the Holy Spirit enters a sinner’s heart, one is led to believe and profess Jesus as Lord over oneself. With this knowledge comes an awareness of one’s own unworthiness and a sense of personal need. Someone who knows that Jesus is Lord knows that he or she is not.

Peter’s first sermon climaxes with a proclamation of Jesus’s divine authority:

Let all the house of Israel therefore know for certain that God has made him both Lord and Christ, this Jesus whom you crucified. (Acts 2:36)

And when the listeners understood who Jesus was, they were “cut to the heart” (Acts 2:37). Knowing who Jesus is left them undone, aware of their sin, wondering what they could do to be saved. Salvation requires knowing you need to be saved, and this requires knowing Jesus can save.

But a Christian knows more than the fact Jesus is Lord; he also knows that “God raised him from the dead.” This is a statement simple enough for a child to believe; indeed, it requires a childlike faith to accept (Matt. 19:13–15; Mark 10:13–16; Luke 18:15–17).

To be raised implies that Jesus died, and to be a Christian you must believe that he died for you. He is the answer to your problem. His death is the key to your salvation. His cross is your only hope.

John Calvin defined faith as “a firm and certain knowledge of God’s benevolence toward us, founded upon the truth of the freely given promise in Christ.” What is God’s “benevolence toward us” if not, at least, the knowledge that Christ died and rose to save us? And what is the foundation of this knowledge if not the “truth” that his salvation rests in God’s promise to save all who turn and trust him?

Asking about the minimal level of doctrinal knowledge a Christian must have is dangerous if one is trying to get out of believing the whole Bible. But if it is asked humbly, the answer is a sweet reminder that, as the old adage goes, the gospel is shallow enough for a child to wade in and deep enough for an adult to swim in. To be a Christian is to cling to Christ as sovereign Lord and risen Savior. In other words, it is to believe you’re a sinner, and his death and resurrection is the only answer to that heinous problem.

No Seminary Degree Required

I want members of the church I serve to realize they don’t need a seminary education to share the gospel. I hope they have confidence in the Holy Spirit’s power to save. And it’s crucial they know the simple truth that God saves sinners through the crucified and risen Lord Jesus. This is a message most can communicate.

No wonder Charles Spurgeon enjoyed recounting the sermon God used to change his heart. An obscure guest preacher at a Primitive Methodist Chapel took Isaiah 45:22 as his text and urged Spurgeon to look to Christ. Speaking for the Savior, the simple preacher said:

Look unto me; I am sweatin’ great drops of blood. Look unto me; I am hangin’ on the cross. Look unto me; I am dead and buried. Look unto me; I rise again. Look unto me; I ascended to heaven. Look unto me; I am sittin’ at the Father’s right hand. O poor sinner, look unto me! Look unto me!

Of course, I want to say so much more than this when I unfold the gospel. I want people to understand the Trinity, the importance of penal substitutionary atonement, the necessity of good works as a response to saving faith, and the inerrancy and authority of Scripture. I’d talk about the second coming, the new heavens and new earth, and the need to be ready for the day of judgment.

True faith will lead you to affirm as much of God’s truth as you possibly can.

Should someone profess faith in Christ and want to join our church, we—like most churches—would require assent to these basic beliefs. Not because we are convinced all of them are essential for salvation, but because we aren’t sure how we can affirm someone as a Christian who denies these truths. True faith will lead you to affirm as much of God’s truth as you possibly can. Louis Berkhof put it well: “The knowledge of faith consists in a positive recognition of the truth, in which man accepts as true whatsoever God says in his Word.”

It is hard to say what, precisely, is the least one must believe to be a Christian. Nonetheless, it’s never wrong to side with Paul: “If you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved” (Rom. 10:9).