"Thus, the Radiance of Drift and Doubt is the sage's only map. He makes no definition of what is right but instead entrusts it to the everyday function of each thing. This is what I call the Illumination of the Obvious." (Zhuangzi, 2:29; Ziporyn)
Those of you who have been reading these posts for awhile will recognize this passage as one of my favorites; I refer to it often.
The subject of the first sentence is "Radiance". Drift and Doubt, wandering where nothing is fixed and sure, result in the Radiance. What is it? It is the Illumination of the Obvious. But what is this?
It is, I believe, a kind of understanding, but not one which can be articulated. It might be compared to the prajna (spiritual insight) of Zen, but I wouldn't want to press it too far. In the context of Daoism, it is that understanding which arises when the understanding of the 'understanding consciousness' comes to an end. Zhuangzi's critique of the knowing mind does not result in despair, as it does with certain existentialist philosophers, but rather becomes a means by which to open the heart and mind to life as it is given. For "Nature speaks, though it has no words." To let it speak, is to allow the Obvious to illuminate.
Those who come to realize the fundamental lack of a firm cognitive foundation for every human aspiration to know the what, why and how of things, and who remain within that cognitive framework, can only declare the absurdity of humanity. The Daoist vision, however, having come to the same conclusions regarding the limits of the discriminating mind, is to put aside that mind and to let Life itself speak and guide.
We know a great deal about life, but we really don't know what it is. Yet, we experience it just the same. Life is the impulse to live. So we live. Life is impartial. So we are impartial. Life is expressed in infinite forms. So we affirm them all.
Zhuangzi shares a practical and behavioral consequence of this openness to Life in lieu of sure definitions; we affirm the rightness of each thing. We let things be what they are. We harmonize with things as they are, rather than despairing that they do not confirm to our desires.
I recently quoted a passage attributed to Zhuangzi which says, "Soaring through the vastness, the Great Understanding enters into me, never understanding where it is brought to a halt." (Chap. 22) This is the Radiance of Drift and Doubt. This is the understanding that need not understand anything. This is understanding which is experiential, not cognitive.
You can check out Scott's writings on Zhuangzi here.