Uncertainty

Bertrand Russel Said:

"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts."

Interesting .... "Clarity", too much of it, means lack of wisdom ? Is it the unsureness that surrounds the thought of human beings that dictates that, or the mere fact that the human capacity (and potential) of knowledge is so limited compared to the vastness of the universe that we inhabit?

Or is it simply that these two are one?