After reading the account of Thomas and his doubt, I have heard some people say doubting is sinful. I think that if that was the case, Jesus would have chastised Thomas. But that is not what happened. Jesus gave him what he needed to alleviate his doubt, and tells him, basically, those who don’t doubt are blessed. And I think that is true. People who never call into question their faith are blessed because they do not have to go through that doubt period.