We look at it, and we do not see it, and we name it ‘the
Equable.’ We listen to it, and we do not hear it, and we name it ‘the
Inaudible.’ We try to grasp it, and do not get hold of it, and we
name it ‘the Subtle.’ With these three qualities, it cannot be made
the subject of description; and hence we blend them together and
obtain The One.
Its upper part is not bright, and its lower part is not obscure.
Ceaseless in its action, it yet cannot be named, and then it again
returns and becomes nothing. This is called the Form of the Formless,
and the Semblance of the Invisible; this is called the Fleeting and
Indeterminable.
We meet it and do not see its Front; we follow it, and do not see
its Back. When we can lay hold of the Tao of old to direct the things
of the present day, and are able to know it as it was of old in the
beginning, this is called (unwinding) the clue of Tao.