The closing story in the sixth chapter finds an impoverished man asking who could have brought him to such an extremity of suffering. He concludes: "I search for some doer of it all but cannot find anything — and yet here I am in this extreme state all the same. This must be what is called Fate, eh?" (6:57; Ziporyn)
This could easily be a summation of Zhuangzi's philosophical point of departure. The idea of "Mystery" is not a fabrication, a god-in-the-machine, but an honest look at the brute realities of our human experience. Shit just happens. Everything just happens. Mystery is not the answer, but the no-answer. The rationalizing mind takes this as an opportunity to despair; the Daoist mind takes it as an opportunity to let go in trust, to transcend, to soar, to wander in joy. Why? Because we can.
No "doer" can be found. This harkens back to that pivotal observation in the second chapter, the conclusion of Ziqi's metaphor of the piping of the wind in the trees: "It gusts through all the ten thousand differences, allowing each to go its own way. But since each selects out its own, what identity can there be for the rouser?" (2:5) What we have is what there is, nothing more. This is our teacher. The Mystery teaches us in deflecting us back to reality as we experience it, not in providing some imaginary resolution to it.
In his discussion of the title of this chapter, "The Great Source as Teacher", Ziporyn contrasts this formula to that which Zhuangzi relentlessly rejects, "taking your own mind as your teacher". This is the rationalizing mind, the one that insists it must know to act, and thus fabricates 'eternal verities' by which to live. Apart from alienating us from the roots of our experience — an emptiness, on the one hand, and a non-rational impetus to life, on the other — these castles in the air only set us up to fall. In the West, where we fell so long ago, we take as the norm what was previously not so. Yet we need not despair at our despair, but can rather take it as an opportunity to be deflected back to our roots.
You can check out Scott's writings on Zhuangzi here.