"Not a single one out of ten thousand who can succeed."

[Serious Buddhist]

Speaking honestly, when you learn Buddhism, do you have the confidence of definitely becoming a Buddha? (Students answer: No.) Apart from lunatics, there is no one with this kind of confidence. If they are not crazy they are foolish. The rest are all hesitant and do not believe. Therefore, out of ten thousand people, there is not a single one who can succeed.

-- Nan Huai Jin in his book: Yogacarabhumi Shastra Commentary

My understanding is that we need to cultivate to the point where all doubts are absolutely erased. Not as a lunatic or foolishly believing it, but having absolute faith after having wisdom.