Used to be, in order to be legitimate a theory had to be provable, there had to be a way to prove it. That a force we call gravity exists is easily provable by even a child. The theory part is 'how'.
Common culture takes theories as fact on a regular basis.
And a 'fact', my dad used to say, a fact is something that always has been true, is currently true, and always will be true, so there is no such thing as a fact because we don't know the future
Pete