Thomas the Twin became Thomas the Witness, and that required an integrated intelligence of what had happened, seeing and touching and hearing to establish faith. But Thomas the Witness became Thomas the Apostle and Martyr, and no one can be an apostle and martyr without venturing beyond what is understood through sight and touch and hearing. And so the blessing Jesus pronounces on those who believe without seeing, will apply later on to Thomas, too.
“Blessed are those who have not seen and yet believe.” What we are to do, what we are to suffer, is not shown to us in advance when we are sent out on our mission. If it were, it would not be a mission. There is none of us, however assured and convinced of the truth of the resurrection faith, who will not at some point have to live without knowing.
The blessing is for all of us, for we are all sent to engage with a world of which we have no foreknowledge. Neither the risks nor the possible achievements have been explained to us in advance.
Faith may look for a well-grounded confidence, but when it has won its confidence, it ventures upon it. That is why faith is active and potent, a force for the condemnation of sin and the liberation of bound souls. It is for that that the Holy Spirit is given.