What's a theory of truth?
Theories of truth are not about the truth of a given statement per se, but rather about what we consider truth to be. The three theories presented below are the current mainstays in epistemology. A statement of fact does not, however, only have to be valid according to one of these. Just as a knowledge claim gets stronger if you can use multiple arguments, just as your arguments become stronger if you can use many different ways to justify them, so your statement of truth is all the more valid if it can meet the criteria for all three.
Pragmatic theory of truth: Something is true if it's useful to you. Keep in mind that useful here is not meant in the same way that you might say you computer is useful for doing homework. Pragmatic theory of truth implies that something is true if it has a predictive value.
Coherence theory of truth: Something is true if it fits in with the rest of one's beliefs and knowledge claims.
Correspondence theory of truth: There is a correspondance between the statement of fact and the fact. This is an empirically based theory.
Each theory has certain limitations. Coherence theory allows untrue statements to be accepted if they fit with previous beliefs, and true statements to be rejected if they don't. Correspondence theory depends on our ability to experience the fact we claim to know. Pragmatic theory rejects something that we can't use right now, but there are many truth that we cannot use at this point and time that are still true noentheless.