Thomas was not there with the other apostles, who had seen the Lord. Eight days later Jesus appeared again. This time Thomas believed and said “My Lord and my God”. Jesus said that blessed were those who believed without seeing. John concluded this gospel by saying that Jesus did many other signs, but these would suffice to have people believe in Jesus Christ. Are you able to believe in Jesus without ever seeing him in person?
“Four more were
The son of Alphaeus,
Who was called the Zealot.”
καὶ Μαθθαῖον καὶ Θωμᾶν, καὶ Ἰάκωβον Ἀλφαίου καὶ Σίμωνα τὸν καλούμενον Ζηλωτὴν,
This section about naming the 12 apostles is similar to Matthew, chapter 10:3-4, and Mark, chapter 3:18. This list can also be compared to the list in the Acts of the Apostles, chapter 1:13. Matthew (καὶ Μαθθαῖον), or Levi, the tax collector, and doubting Thomas (καὶ Θωμᾶν) in John, chapter 20:19-29, are mentioned elsewhere in the gospels. However, the other 2 apostles are not mentioned by name elsewhere in the gospels, James, the son of Alphaeus (καὶ Ἰάκωβον Ἀλφαίου), and Simon the Zealot (καὶ Σίμωνα τὸν καλούμενον Ζηλωτὴν). Both of these men have some confusing comments about them in the other listings of the apostles. In Mark 2:14, Levi or Matthew was called the son of Alphaeus just as James is here. However, in the list of Mark, chapter 3:18, he also called James, the son of Alphaeus as here. Were they brothers? Mark also called this Simon the Cananaean. Either this Simon was a Jewish zealot or a Cananaean. Besides Simon, the leader called Peter, there was a mention of a Simon who was a leper and Pharisee Simon. So that there were a lot of Simons in the gospel stories.