Just a quick reflection, food for thought:
How would it change your spiritual life if you knew God was real?
This may seem like a funny thing to say, since I realize I'm writing largely to a believing audience. But in fact, we can believe something officially without believing it in a way that puts everything on the line. When I vote, I'm stating officially that I believe this person or this party will best represent me. But if the party or person lets me down (they almost inevitably do, eh?), I can just as easily walk away from it/her/him without too much trouble. It's not exactly the same thing with belief in God, but to be honest, most of us do go through life without ever seeing the sort of concrete evidence Thomas was looking for.
Historical records appear to show, incidentally, that Thomas -- often dismissed and dissed as the faithless disciple -- went on to have a powerful ministry spreading the good news of Jesus Christ, and was eventually martyred for his faith.
God knows each of us so well. He asks all of us to believe by faith, but He also knows what each of us needs to move forward into deeper commitment. Even if He never gives you concrete evidence that He's real and that Jesus is exactly who He said He was, it is still a good question: How would it change your life if you knew God was real? How would your bond with Him change, how would your prayer life change, how would your priorities and focus change? If you're a bit like Thomas (as I am), remember -- Jesus loved Thomas, and met him where he was. Thomas was honest with Jesus, after all. That's always where a deeper relationship begins.