We often call him “doubting Thomas,” but if we look more closely at the Gospel account, we might learn something new about the great faith of this holy apostle.
Now a week later his disciples were again inside and Thomas was with them. Jesus came, although the doors were locked, and stood in their midst and said, “Peace be with you.” Then he said to Thomas, “Put your finger here and see my hands, and bring your hand and put it into my side, and do not be unbelieving, but believe.” Thomas answered and said to him, “My Lord and my God!” Jesus said to him, “Have you come to believe because you have seen me? Blessed are those who have not seen and have believed.”
St. Thomas the apostle was nick-named Didymus, which means “the twin” and St. Thomas Aquinas offers an interesting explanation of this: the name “twin” could be taking from the apostle’s doubting. Indeed, one who doubts is mid-way between two opinions: while holding to one, he fears that the other might perhaps be true. Thus, the apostle’s mind was as a twin, struggling between two competing ideas—Had Christ risen, or was he dead? (Commentary on John 20.5)
Of course this doubt was put to rest when Jesus appeared and showed his wounds to St. Thomas the apostle, who then touched them and believed. But how can this be called faith? We know that faith regards things which are not seen (Hebrews 11:1—faith is “the conviction of things not seen”), but the apostle did not believe until after he had seen the risen Christ. So how is this faith, when he had already seen?
St. Thomas Aquinas, following St. Augustine, offers a most ingenious explanation of this verse: St. Thomas the apostle saw one thing, but believed another. He saw the humanity of Christ, but believed in his divinity. He saw that Christ had risen from the dead as a man, but believed in his eternity as God. (Commentary on John 20.6)
Thus, St. Thomas the apostle cries out: “My Lord and My God.” This is the clearest affirmation of the divinity of Christ that any of the apostles ever gave before Pentecost. This, then, is the substance of the apostle’s faith: he believed and proclaimed the divinity of Christ; something which none of the other apostles had yet done.St. Thomas the apostle, though he had doubted, nevertheless came to believe; and, in his unshakable faith in the divinity of Christ, he has given a lasting testimony which has served to be the foundation of the faith of countless generations of believers who, imitating this great apostle, have cried out: “My Lord and My God.”
For more on how Christ entered the locked room (according to the quality of his risen body), look here.