Hello! My question concerns the word, "theory". Can a theory be considered fact, and what gives one theory more credibility than another? I know that some theories are empirical, and can be tested scientifically for validity. So if a theory such as evolution seems a fact, why is it still called a theory? Should it not be fact? Obviously, some non-empirical theories, like String Theory, can't as yet be tested, and are questionable. But scientifically, do empirical theories get closer to truth, and can some be called true?