"NOT KNOWING IS THE MOST INTIMATE."
The stupid person says, "I know"; the intelligent person comes to know that "I don't know." But there is a transcendence of both when only silence prevails. Nothing can be said, nothing can be uttered.
Enlightenment is always sudden because it is not an achievement; it is already the case. It is only a remembering, it is only a reminding, it is only a recognition. You are already enlightened; you are just not aware of it. It is awareness of that which is already the case.

Any day when your mind collapses, when you cannot hold it together any more, there is bound to be sudden enlightenment. It is not an attainment, hence it can happen in a single moment, instantly. Society has forced you to forget it; taoism is to help you remember it.