Thomas is one of the original twelve disciples. (Matthew 10:3) The first time anything is actually known about him is in John 11:16. Lazarus has died and Jesus is getting ready to go to him. This is in Judea. Yes, that Judea, where the Jewish leaders are out to get Jesus. Thomas's hearty reply to the others' hesitancy is, "Let's go. If Jesus dies, we'll die with him." Sounds like a pretty salty guy.
The next encounter is John 14:5. The preceding verses are the famous "Let not your heart be troubled...and where I go you know the way" speech. Thomas appears to have drawn a blank here because he looks at Jesus and says, "How do we know where you're going or how to get there?" Clearly Thomas has a good grasp on the down-to-earth things. He understands the danger in Judea. He gets lost when it comes to spiritual things--can't feel it, can't touch it kind of guy.
This really jumps out in the verses John 20:24-29. Jesus has been crucified. He's gone, out of sight. When Jesus appeared to the disciples the first time, Thomas wasn't there. It's curious that he was a no-show. He must have thought that Jesus really was dead. But, when he's with the disciples the next time, they try to tell him that Jesus is alive. Boy, does he bow up. He stands his ground and says, "You can't convince me that's true. The only thing that will convince me is if Jesus shows up and I can poke my fingers in the nail holes and my hand in his side." What do 'ya know? Jesus appears and Thomas is instantly humbled. The man who has to have everything in "black and white" is persuaded. Thomas is living proof that hard-headed, stubborn people can be brought to a saving knowledge of the Lord. It just takes some doing.