Although there is a persistent history of claims that Thomas was the apostle to India, and there is a Mar Thoma Church (St. Thomas Church) there that claims him as its founder, very little hard historical evidence is available about Thomas beyond his mention in the lists of apostles in the synoptic Gospels, four anecdotes in John's Gospel in which he plays key parts, and the “doubting Thomas” sequence in John 20, which will be taken up in Chapter 9.

John's Gospel gives its first brief look at Thomas in Chapter 11, where Thomas responds to Jesus' sorrow about the death of Lazarus: “Then Thomas, who is called Didymus, said to his fellow disciples, ‘Let us also go, that we may die with him.’” Though less specific than Peter's and Nathanael's confessions (“truly you are the Son of God”), this displays deep faith in Thomas, who puts his fate entirely in the Master's hands.

John's next glimpse of Thomas comes in another well-known passage on Jesus' divinity and his way of salvation, chapter 14:1–7. Jesus describes his intention of creating “many mansions” in his Father's house for his disciples, and says they know where he goes and how. But Thomas interrupts to say, “Lord, we know not whither thou goest; and how can we know the way?” To which Jesus replies that he is the way, the truth and the life; no man comes to the Father except by him. This is probably the most specific declaration in the Bible by Jesus of being the exclusive way of eternal salvation.