Thomas was not with the other Apostles, when Jesus appeared to them in the locked room, and as soon as the other disciples saw Thomas they cried out, “We have seen the Lord!” However, Thomas was not so easily convinced and told his fellow disciples, “Unless I see the mark of the nails in His hands, and put my finger in the mark of the nails, and my hand in his side, I will not believe”. Ever since he has been known as Doubting Thomas.
But maybe we do Thomas a dis-service, for perhaps he remembered the words of his Jesus Christ, Who once proclaimed, “If anyone says to you, ‘Look, here is the Christ!’ or, ‘There He is!’ do not believe it. For false Christ’s and false prophets will appear and perform great signs and miracles to deceive even the elect, if that were possible. See, I have told you ahead of time”.
Maybe Thomas rather than doubting due to disbelief did not wish to fully believe until he had substantial proof, in order to keep the word of Christ. After all we don’t know where Thomas was while the other disciples cowered in that locked room, maybe he alone was continuing to proclaim Christ in word and deed.
While St Thomas is often referred to as Doubting Thomas, in the Greek Orthodox Church he is known as Believing Thomas. I like that title far more, after all Thomas doubted for only a week and even then it was not out of lack of faith but out of lack of understanding, and he never did put his fingers and hands in Christ’s wounds but as soon as he saw him cried out “My Lord and my God!”
That kind of faith comes from certainty not doubts.