Jesus' statement to the Capernaum official in John 4:48, "Unless you see signs and wonders, you will not believe," is meant as a reproach and shows that Jesus was put off because the man required proof before he would believe, whereas true faith required no proof. Evidence to support this idea may be found in John 20:28, where the resurrected Jesus appears to rebuke doubting Thomas on similar grounds: "Have you believed because you have seen me? Blessed are those who have not seen and yet have come to believe."

Scholars additionally maintain that the author of the "signs source" from which the author derived his stories of Jesus' miraculous deeds had a basic understanding of the relationship between Jesus' miraculous deeds and faith: Jesus' deeds prove that he is the Son of God. But the author of John had a more nuanced view of the matter. For him, the miracles were not unambiguous proofs, they were literally significant only to those who were open to the truth about Jesus, that is the one who reveals God. This is why some people could benefit from Jesus' miracles and yet still not understand what they meant (e.g., see, 2:23-25; 3:2-10; 6:26; and 11:45-48).

Other scholars take a different position. For them, Jesus' miraculous deeds in the Fourth Gospel are not proofs of his identity but are clear and necessary signs of who he is. The author of John believed that no one could understand Jesus as the one sent from God without first seeing what he had done. By reading the Gospel in this way, Jesus' statement in 4:48 is not a reproach but a statement of fact: no one will believe without seeing Jesus' signs, for these are deeds that reveal who he is. This does not mean that everyone who sees these deeds necessarily comes to faith, but everyone who comes to faith has seen these deeds.

But what about those who were not there to see the the miraculous deeds? For the author of John, these people can come to faith by hearing of these signs, the very reason he wrote his account as seen in the conclusion that the took over from his signs souce: "Jesus did many other signs in the presence of his disciples, which are not written in this book. But these are written so that you may come to believe" (20:30-31).

(Adopted from Bart D. Ehrman's The New Testament: A Historical Introduction to the Early Christian Writings, Fourth Edition. New York: Oxford University Press, 2008.)

See Peculiarities Of The Gospels