There’s a way of reading Dàoist philosophy according to which there is one great dào, and the Dàoist aim is to achieve some kind of relation to that one dào, presumably some kind of union.
As I understand it, this sort of reading implies that once you’ve achieved union with the dào, this will carry you through life no matter what it brings you. And this, I think, sits poorly with much of what we read in Dàoist texts. Verse 1 of the Dàodéjīng in particular is suspicious of the very idea of a single, constant dào; and the Zhuāngzǐ often seems to value a recognition of what is particular to the various situations we face.
So I suggest (I’m largely following Chad Hansen on this) that it would be better to think of dào as differing in different situations, and in ways that are largely unpredictable. Dào is thus not a single thing that one could relate to, or achieve union with, as a whole; no union we could achieve with dào now would carry us through the unpredictably various situations we are liable to face in the future.
(One could put my suggestion by saying that there are different dàos in different situations, but I prefer to follow the classical Chinese, in which “dào” is normally a mass noun.)
This implies that the Dàoist aim cannot be to achieve once and for all a union with the one great dào, it must instead be to maintain an openness to the different dào in different situations—just as, for example, the monkey keeper in Book 2 of the Zhuāngzǐ is open to the dào of his monkeys (in particular, to their preference for having their bigger meal in the morning). This is how I understand the value frequently placed in Dàoist texts on flexibility; I take it to be at the heart of the ideas of míng 明 (illumination) and of the pivot of dào in Zhuāngzǐ 2.
Should this openness itself be conceived of as a dào? This may be an issue over which Dàoists disagreed. The butcher in Zhuāngzǐ 3 loves dào because it takes him beyond skill—that is, beyond any dào he has previously mastered, so he can deal with the situation before him. But the swimmer in Zhuāngzǐ 19 denies that he has his own dào, saying he swims instead according to the dào of the water.
If we take openness to the different dào in different situations to be a dào, then it is a short step to thinking about this as the same as the dào according to which phenomena arise in nature. Perhaps it is in this sense that the texts sometimes tell us that dào is prior to heaven and earth.