Do not think that every critic is opposed to the Holy Spirit; and not everyone who rejects your witness is wayward or perishing. Here John shows that among the many events taking place in the forty days before Christ’s ascension, there was a peculiar one. This shows how grace creates faith in the human breast, not by works, intellect or logic, but by grace and mercy alone.
Thomas was a pessimist, seeing only the gloomy side of events. He had to probe to the depths of the matter in order to reach the plain truth (John 11:16; 14:5). He was thoughtful, solving issues mentally. He had seen in the death of Christ the loss of meaning in life. He became separated from the circle of disciples, and did not see Jesus that first Sunday, when Jesus appeared in the midst of his followers.
Thomas may have argued that the appearance was just a Satanic delusion – that an evil spirit had taken on the form of Christ to lead them astray. No surprise then, that he insisted on foolproof evidence to what had happened, that Jesus had come in person. He would not be convinced unless he felt the marks of the nail-prints. In this way, he bargained with God to believe, wishing to see before trusting.
So he returned to the company of disciples, who were full of joy on account of the appearance of Christ to them. He, however, was sad, saying he wanted to be sure that Jesus had risen.