I think it should be made clear, however, that given enough evidence, a theory could be considered damn close to truth. Theories are applied every day (take any electronic device you own for example), but the engineers who work on these devices don't have any doubt about well-supported theories. They don't go, "oh, well we can't do that, because it's just a theory."
Our language really needs a word for truth when it means "completely true, proven, without a shadow of a doubt" and just "Possibly or most likely true, 'for all intents and purposes true'" or something.
I guess what I'm trying to point out is that theory doesn't imply uncertainty. It's not like, "oh, that calculus thing is just a theory, so forget that."
Bassoon, n. A brazen instrument into which a fool blows out his brains.