So without further ado, a favorite passage of mine.
As always, the words say it all: the Hebrew word for doubt is safek, and for certainty, vadai. Now these commonly used words are not to be found in Scripture. Nowhere does the Torah mention them; both are of Rabbinic origin. If the essence of an idea is contained in the Torah word for that idea, and we find that there is no word for a particular idea we encounter, it surely means that at the deepest level, that concept does not exist... If no word exists in the Torah corresponding to a thing we perceive in the world, that constitutes a strong suggestion that the thing we are perceiving is illusory. Someone has painted it up on the screen of reality, but it is not being projected from the source. And of course - the world as formed by its root in Torah contains no doubt: things either exist or they do not. There is nothing in the world that exists "doubtfully," tentatively; doubt is a problem of our perception, not an objective reality. (And if there is no doubt, there is no certainty either - certainty exists only where doubt is a possibility; if there can be no doubt there can be no certainty, a thing simply "is.")
The primal, pristine world is clear and open. We opacify and confuse it. The word for "doubt" is of human origin; it is a description of the damage we do to our own perception.