I've been dancing around Lusthaus's major theme in "Aporetics Ethics in the Zhuangzi" (Hiding the World in the World) now for several posts and I am now going to make a final stab at summing it up.
An aporia is a point of absolute undecidability (unknowability). Using skeptical arguments — that all distinctions, moral or otherwise, are perspectivally determined, for instance — Zhuangzi brings us to the point of aporia — we don't know for sure what is 'right' and what is 'wrong'. This does not become an occasion for a complete dismissal of all knowing (radical skepticism), however, but rather a foundation for ethical action — “going along with the present 'this' ('right')." This is because Zhuangzi is a "critical thinker" whose elimination of certain propositions by way of skeptical argument is for the purpose of finding the 'best' way, rather than to discard all ways. He arrives at an ethical (what should we do?) conclusion by way of an epistemological one (how do we know?) because both questions share the attribute of being merely discriminations of the mind.
This seems logical enough on the surface and we can affirm it on that basis, but somehow I think it completely misses the spirit of Zhuangzi. It seems to suggest that Zhuangzi has arrived at his way by means of logical argument, and nothing could be further from the truth. His "Illumination of the Obvious" is a phenomenological appreciation of experience that ultimately is an affirmation of life, not of the machinations of the mind. This is the whole point. It is very much like his knowing of the happiness of fish — he knows it because he sees them doing what they do. Huizi wants to establish rational grounds for this — something that Zhuangzi, nor anyone else, can do. Zhuangzi makes the necessary leap that is the affirmation of life (as, in fact, does Huizi who asks Zhuangzi how he knows because he too knows). It is ultimately a mystical move. Reason cannot go there. Common sense, in this sense, is a mystical movement. (Since all is Mystery, how could it be otherwise?)
The Illumination of the Obvious is Zhuangzi's amplification of this basic dimension of human experience which we all exercise but largely fail to fully appreciate. We are rooted in life, and life is beyond understanding. Ultimately, Zhuangzi suggests we take an affirming and mystical plunge into life. That's all. Release into the human experience; flow with the way things are; accept the "inevitable"; harmonize with the life experience by disallowing the mind's propensity to reject and denigrate what it does not 'like'. All the rest follows from this.
You can check out Scott's writings on Zhuangzi here.