According to the Dictionary app, which I got when upgrading to Mac OS 10.9.5 (Mavericks), these words have something like the following meanings:
Fact = a thing that is indisputably the case
Theory = a supposition or a system of ideas intended to explain something
Belief = something one accepts as true or real; a firmly held opinion or conviction
(i.e. a religious conviction); trust, faith, or confidence in someone or something
(paraphrasing is mine – RSB)
These are (slightly) paraphrased, but they do indicate the meaning of these terms, as I have always understood them. I find these definitions to be quite fascinating.
Note that a “fact” is something which is “indisputably the case.” That’s curious, at least to me, because we all know that for a long time it was “indisputable” that the world was flat and that the Universe revolved around the Sun. That means that, during that time, these were “factual” statements. Then things changed and we felt compelled to believe otherwise. So this is problematic because it creates problems with the whole idea of a “fact.” It doesn’t fit the definition above very well, as something “indisputable” shouldn’t be capable of such change. I think that that may be the point; that if we were to make the definition of “fact” more complete, it would have to include some qualification that deals with the reality that we are always dealing with the current state of knowledge. After all, a flat Earth and the Copernican model worked fairly satisfactorily until new discoveries started poking holes in it. At that point, these “facts” became “disputable” and thus lost the status (in my opinion) of being facts. So, what did they become?
This is where “theory” enters into the picture. A “theory” attempts to explain something, usually based on some study, experimentation, etc., but recognizes that there is information missing, or unavailable which does not allow this explanation to be considered “indisputable.” Thus, Einstein’s General Theory of Relativity and the Theory of Evolution (Note: this is often misreferenced as Darwin’s Theory. He did provide much evidence and argument to support this idea, but he didn’t create it.), are, properly, “theories” because we don’t have enough evidence to consider them “indisputable,” but they seem to fit the evidence we have pretty well. (My apologies to any believers in “Creation Science” which seems much more religious than scientific to me as it seems to begin with a conclusion [that the Biblical account of creation is true] and then seems to try to force the evidence to support that conclusion.)
That gets us to the proper (again, in my opinion) use of the term “belief.” I said above that this term refers to something “one accepts as true or real….” I think the most important word here is “accepts.” Acceptance does not require any sort of proof, or even specific evidence. If you wish to accept that aliens landed at Roswell in 1947, based on conflicting reports and less than adequate (publicly revealed) evidence, I have no problem with your right to believe that, but your belief doesn’t make it a fact, as we have defined the word here. It is not “indisputable.” The same thing is, or should be, true of the Bible and many other writings of a religious nature. If some people wish to accept the Bible, or other works, as being fully and absolutely true, it seems to me that they should have the right to do so, but they have an obligation to admit that their “belief” doesn’t make it a “fact.”
I think this is indicative of one of the real problems which exists in the U.S. today. Far too many people, of a wide variety of beliefs, seem to be under the impression that, since “this is what I believe,” the rest of us should have to believe it (at least accept it as Truth [factual]) as well. I don’t think that’s how or why this country was created and this practice seems to be responsible for much of the turmoil in present day society. Whether we are speaking of race, religion, politics (all too often these three seem to become mixed up together) or a number of other issues, this insistence that everyone ought to believe the same thing seems to be advanced frequently (occasionally rather subtly) and seems to serve only to close off discussion of the real issue at hand and lead to arguing about beliefs. That seems counterproductive.
I’d like to urge people to just “chill” a bit and take a moment whenever conflict starts to develop to carefully listen to the other person’s ideas. I’m certainly NOT suggesting that you should back down from your own beliefs, but actually listening to the other person’s point just might help you to understand where the common ground may be and provide some means for avoiding the “you believe that and you’re wrong” kind of discussion which so often develops and help both of you to focus on how to resolve, or at least reduce, the tension which often prevents productive actions. I think it’s worth thinking about, at least.