It is rationalism, the belief that only reason can give us proper guidance in life, which he [Zhuangzi] rejects. Rationalism cannot forget the words. No passage better demonstrates his affirmation of reason while recognizing its limits than this one also previously cited in part:
“Therefore, when the rationalizing mind restfully settles in what it cannot know, it has fully realized itself. The proof that uses no words, the Dao that is not-a-dao—who can ‘know’ them? The ability to in some sense ‘understand’ these I call tapping the Heavenly Reservoir. It is poured into, but never full, partaken of, but never emptied. Yet we are ever-not-knowing from whence it comes. It is simply life itself. Let’s call it The Dark Brilliance.” (Zhuangzi 2:44)
When reason discovers its limits and we let that point us to where reason cannot go it has realized its fullest potential. Zhuangzi agrees with Laozi that “the dao that can be spoken is not the Constant Dao” (Daodejing 1). Daos are spoken guidance, articulated paths. They are necessary, but should not be taken as representing Truth; they too need to be forgotten. This dao as expressed above points us to the inexplicable mystery of our own self-arising, the life experience that we are, and suggests another more immediate and unmediated way to experience it. This experience of the up-welling of life he calls the Heavenly Reservoir and The Dark Brilliance. It is dark because its source remains shrouded in utter Mystery. It is a Brilliance because we experience it as the deepest intimacy possible. And we can speak of it as well. Only we should not let our words forget the Mystery. Nor should we take the Heavenly Reservoir for some “thing”, a true nature—its roots are in Mystery and thus it too is Mystery. It is the occasion of life, a happening without apparent causation.