Why does John place the story of “doubting Thomas” at the climax of his gospel? Because John’s whole purpose is to call people to believe in Jesus of Nazareth—his claims about himself, his ministry, his death for sin, and especially his resurrection from the dead—even though they have never seen him.

In fact, out of about 250 times the New Testament uses the verb “believe” (pisteuō), nearly 100 of them occur in John’s gospel alone. And what is even more interesting is that John never uses the noun form, “belief” or “faith” (pistis). For John, belief is always an active idea, a verbal idea.

But John is not merely interested in instilling belief in those who have not yet embraced the good news. He is just as interested in strengthening the belief of those who are already followers of Jesus as well.

We can see this emphasis in the Gospel of John through the way John emphasizes the faith of Jesus’s own disciples at the beginning of the gospel and later toward the end and climax of the gospel. The first person in the Gospel of John who believes is Jesus’s disciple Nathanael.

Nathanael answered him, “Rabbi, you are the Son of God! You are the King of Israel!” Jesus answered him, “Because I said to you, ‘I saw you under the fig tree,’ do you believe? You will see greater things than these” (John 1:49–50).

The next time believing is mentioned it is Jesus’s disciples who believe after the miracle of the water turned to wine.

This, the first of his signs, Jesus did at Cana in Galilee, and manifested his glory. And his disciples believed in him (John 2:11).

Later, in John 2, after Jesus cleanses the temple and declares, “Destroy this temple and in three days I will raise it up” (John 2:19), John forecasts the fact that Jesus’s disciples would later remember that he had said those words and believe:

When therefore he was raised from the dead, his disciples remembered that he had said this, and they believed the Scripture and the word that Jesus had spoken (John 2:22).

After this passage, however, John’s Gospel turns away from the issue of the disciples believing, and gives attention solely to others believing—Nicodemus (John 3), the woman at the well (John 4), the Pharisees (John 5), the 5000 (John 6), the people at the Feast of Tabernacles (John 7), the man born blind (John 9), Martha at Lazarus’s tomb (John 11), to name a few.

But after the people of Israel in general refuse to believe in him (John 12:37), John turns our attention once again to Jesus’s own disciples. Often in the private conversation that Jesus has with his disciples in John 13–16 the subject turns to their believing in him (e.g., John 14:1, 10–12; 16:25–33). Twice Jesus tells his disciples what is about to happen to him in his passion “so that” when it does happen they will remember what he told them and believe (John 13:19; 14:29).

Furthermore, in the hour before his arrest and the beginning of his trial, Jesus prays to the Father,

“I do not ask for these [disciples] only, but also for those [disciples] who will believe in me through their word …” (John 17:20).

So when Thomas declares in John 20:25,

“Unless I see in his hands the mark of the nails, and place my finger into the mark of the nails, and place my hand into his side, I will never believe,”

the matter of one of Jesus’s disciples fully embracing him in faith is not a new thing. Jesus had been preparing his disciples for this day his whole ministry with them. The other disciples believed, but they had already seen Jesus (John 20:24). Thomas’s reaction was likely similar to theirs the first time they beheld Jesus’s hands and side.

So, Jesus says to Thomas,

“Put your finger here, and see my hands; and put out your hand, and place it in my side. Do not disbelieve, but believe” (John 20:27).

This call, “Do not disbelieve, but believe,” becomes the very reason John writes his gospel.

Thomas answered him, “My Lord and my God!” Jesus said to him, “Have you believed because you have seen me? Blessed are those who have not seen and yet have believed” (John 20:28–29).

Those “blessed” people include you and me, if you are his believing disciple. We have never laid eyes on Jesus, yet we are entrusting him with our lives and eternal destinies. But think of John’s audience, as he writes this gospel from Ephesus, sixty years or so after Jesus has risen and ascended to the Father. Do you think there were any in John’s original audience who had actually laid eyes on Jesus either? Precious few, if any.

In fact, Luke, technically the most prolific author of the New Testament, relied solely on second-hand testimony when writing his gospel, and yet writes so that we can know the “certainty” of the things said about Jesus (Luke 1:1–4)

We can wonder if the writer of Hebrews even saw Jesus himself, since he seems to say that he also received his understanding second hand (Heb 3:2b); yet this testimony is firm enough for him to warn his readers that they will “not escape” if they “neglect such a great salvation” (Heb 3:3–4).

Peter is also captivated by this idea that people embrace Jesus based solely on the witness of testimony. He writes to commend the followers of Jesus,

Though you have not seen him, you love him. Though you do not now see him, you believe in him and rejoice with joy that is inexpressible and filled with glory, obtaining the outcome of your faith, the salvation of your souls (1 Pet 1:8–9).

So Thomas’s experience is very rare. For he was one of the very few people in salvation history who actually was in the presence of Jesus—the presence of the risen Jesus, still bearing the marks of his crucifixion. But for the rest of us who claim the name of Christ, believing in Jesus has always been a matter of believing the witness, believing the testimony of those who did see, though we cannot. For this reason, John explicitly states the purpose of his gospel immediately after the story about Thomas.

Now Jesus did many other signs in the presence of the disciples, which are not written in this book; but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name (John 21:30–31).

John writes this gospel for us, so that we believe and continue to believe and know real life in his name. After all, this “faith,” Jude tells us, was delivered to the “saints” (Jude 1:3). So, do not rest on your believing as a past action. Continue to read the gospel story. Reflect. Rehearse. Marvel. Wonder. And believe.