Doubt, in a religious sense, has always been seen as the dark and negative twin of faith. Thomas was scorned for wanting to investigate Jesus's wounds. Doubting scripture is seen as a sin of pride. And doubting God's word was what led to the original sin.
Why is doubt so badly cast? Because churches want strong, faithful followers who will forge ahead for their cause, not hesitant doubters worrying about what lies in ambush to the sides.
But ours is pretty much a post-religious society... so have things changed? Well, a little. But too many teachers would rather read out Newton's laws or the Theory of evolution from a textbook than answer the 'smart-alecky' question-askers' doubts.
What you won't hear in a classroom is that for every scientific theory that is now high-school gospel, somebody had to first doubt the theories that came before. Doubt is always the first step towards knowledge. (In Adam and Eve's case, the knowledge of good and evil.)
So, I now proclaim: doubt! Doubt everything you are told! (And give your teachers a nervous breakdown.) 8^) After all, the most interesting parts of all theories are often reached only through asking those little nagging questions: