Who said the belief had to be certain? It might very well be tentative. Many of my beliefs are tentative.
That is actually a good point.
I tend to think in black and white when it comes to belief. I keep forgetting that others don't.
I always equate belief with a "feeling" (if you like) of certainty and that is my meaning when I discuss it.
In my terms I hold no beliefs unless I am absolutely certain of them.
Then again I also follow the scientific method of "tentativity" which kind of leave me with no beliefs at all unless they are in observable facts.
ie. I believe that OH- reacts with H+ to make water. I have observed it. I have measured it. It is a scientific fact.
I do not "believe" in the TOE even though I see it as a very very strongly supported theory. It is not yet an observable fact.
I do believe in evolution (the fact that is). It has been observed and recorded.
I realize I am not using the word "believe" in quite the same way as you are, although I keep forgetting that during discussions. The trouble is that I don't know what other word to actually use in its place to get my meaning across.