it shows the episode that gave rise to the term "doubting thomas" which, formally known as the incredulity of thomas, had been frequently represented in christian art since at least the 5th century, and used to make a variety of theological points. according to st john's gospel, thomas the apostle missed one of jesus's appearances to the apostles after his resurrection, and said "unless i see the nail marks in his hands and put my finger where the nails were, and put my hand into his side, i will not believe it." a week later jesus appeared and told thomas to touch him and stop doubting. then jesus said, "because you have seen me, you have believed; blessed are those who have not seen and yet have believed."