"However vast heaven and earth might be, however multitudinous the ten thousand things, the source and teacher of all of them is intentionlessness." — Guo Xiang (252-312) (Zhuangzi; Ziporyn)
"Truly, if one uses the Way as one's instrument, the results will be like the Way." (The Way and Its Power, XXIII; Waley)
Intention is purpose. There is none. Reality simply happens; it simple "is"; there is no ulterior motive. This, at least, is how philosophical Daoism sees things. Is it true? We cannot know. Yet, not knowing, Daoism takes the position that a position need be taken. We either orient ourselves toward purposiveness, or we do not; and the suspension of a position, one way or the other, effectively means to live without purpose.
There are those who would argue that because the human yearns for purpose, there must be purpose to be had. This yearning is, after all, 'natural', and what is natural has its fulfillment. The 'spiritual' thought of the West has tended toward this position; that of the East, toward its opposite — this yearning is an aberration, and the cause of all suffering. Somewhat ironically, the East meets the West, in its most extreme scientism, in seeing the Universe as purposeless.
Yet Daoism takes intentionlessness not as a negation of humanity, but as its guarantor. "Go and be thou likewise." In the absence of known (or knowable) purpose, we are invited to explore the implications of purposelessness and find freedom from yearning there. It is our "teacher".
Guo might have said that Reality is intentionless, that it has this quality. But he says (at least in translation) it is intentionlessness, as if suggesting this as its most essential nature. To harmonize with Dao is to harmonize with this. To be this. To just be.
Where there is intentionlessness, there is, of course, no such concept; the idea only arises out of the human yearning for purposefulness. This alone should suffice to demonstrate the relative character of every human attempt to understand Reality. It is all a tentative accommodation with what is beyond our understanding. The point is not to define Reality, but to come into accord with it as apparently manifest.
When Guo says that intentionlessness is our teacher, he is inviting us to spend the contemplative time necessary for it to become an experience, rather than just an idea.
You can check out Scott's writings on Zhuangzi here.