The seed of mystery lies in muddy water. How can I perceive this mystery? Water becomes clear through stillness. How can I become still? By flowing with the stream.
The tao that can be told is not the eternal Tao The name that can be named is not the eternal Name. The unnamable is the eternally real. Naming is the origin of all particular things. Free from desire, you realize the mystery. Caught in desire, you see only the manifestations. Yet mystery and manifestations arise from the same source. This source is called darkness. Darkness within darkness. The gateway to all understanding.
Clay is fashioned into vessels; it is on their empty hollowness that their use depends. Doors and windows are cut out to make a dwelling, and on the empty space within, its use depends. Thus, while the existence of things may be good, it is the non-existence in them that makes them serviceable.