"Hence, when the understanding consciousness comes to rest in what it does not know, it has reached the utmost." (Zhuangzi, 2:36; Ziporyn) This is a pivotal point in Zhuangzi's philosophy. It is the condition that facilitates going beyond; it is the point of departure for 'spiritual' wandering. It follows a discussion of the futility of debate. "Wherever debate shows one of two alternatives to be right, something remains undistinguished and unshown. What is it? The sage hides it in his embrace while the masses of people debate it, trying to demonstrate it to one another." Here we enter the realm of the mystical.
What is this mystical experience? Zhuangzi describes it as the "Shadowy Splendor". It is a splendor in that it brings all manner of good stuff to one's inner experience: joy, freedom, peace. It is shadowy because it is beyond knowing and thus beyond articulation, can only arise in their absence, and does not emerge better informed. It is not a spiritual way of knowing. It is not prajna, if by this we mean a kind of spiritual insight that reveals some ineffable reality. Zhuangzi never envisions anything beyond "the Radiance of Drift and Doubt". His spiritual freedom emerges from these and remains these. If "enlightenment" is understood as revealing something, then his way falls infinitely short of it.
Here, it is worth noting that "Shadowy Splendor" is but one interpretive rendering; Mair has "Inner Light". Such ambiguity might disturb us, but would, I suspect, have made Zhuangzi smile. Personally, I don't have the knowledge or tools to judge between the various renderings. The reason I favor Ziporyn generally is simply because I have the sense that he has a sense of the spirit of Zhuangzi, and I sense this because it echoes my sense of the spirit of Zhuangzi. It's all very "shadowy", is it not?
You can check out Scott's writings on Zhuangzi here.