You have probably heard that it is bad to be a "doubting Thomas." I have often thought that Thomas had a bum rap. As Biblical characters go, Thomas is a pretty good role model. The Judeo-Christian scriptures are rich with multidimensional characters. Even the heroes are ordinary, complicated people with strengths and frailties. Thomas didn't happen to be in the room the first time Jesus appeared to the disciples after the resurrection. His bad reputation started when he didn't believe that Jesus was raised from the dead, based solely on his friends' word. "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."
What we see in Thomas' example is that doubt is a relational feeling. Doubt retains the idea of struggling with belief, even a desire to believe or at least seek out the available evidence.
Though I believe the evidence for God and the evidence of the resurrection of Jesus is all around us, we all have seasons of doubt. Perhaps, for some, the doubt comes from hard times of trial or loss. For others, doubt may be rooted in seeing supposedly good Christian folk do unconscionable things. There are even many who may never have really believed in God, but have had enough of a glimpse of God's love to begin to doubt their lack of belief.
These doubts are not an abandonment or dismissal of God, but are themselves evidence of a relationship with God — however troubled that relationship may be at the moment. The idea is not to dwell in the midst of these doubts and trials, but accept the doubt as an opportunity to explore our relationship to God. Peter, another of Jesus' otherwise faithful disciples, had denied Jesus leading up to his crucifixion and had doubted the testimony of the women who were the first witnesses of Jesus' resurrection. Though Peter had his doubts, he acted in faith by jumping up and running to the tomb to see for himself. Likewise, Thomas acted in faith by claiming his need to see Jesus to fully believe.