Happy feast of St Thomas to all who follow the older Calendar! (Why is it, by the way, that Anglicans of a certain spikiness spell it "Kalendar"?)
His doubts, by the providence of God, were permitted that he, coming to touch the Risen Christ's Sacred and Glorious Wounds, would thereby strengthen our faith, by confessing the invisible Godhead having touched the Word Who is Life, saying: "My Lord and My God" - which should be every man's prayer at the Elevation at Mass, when the Divine Victim is lifted up that He draw all men unto Him.
DOMINUS MEUS ET DEUS MEUS!
[Image of the Elevation of the Chalice of Christ's Precious Blood at a priest's first Mass - hence the assistant priest in cope - courtesy of the Priestly Fraternity of Saint Peter, available from http://fssp.org.]