Tao Te Ching by Lao-tzu

The Tao that can be trodden is not the enduring and
unchanging Tao. The name that can be named is not the enduring and
unchanging name.

(Conceived of as) having no name, it is the Originator of heaven
and earth; (conceived of as) having a name, it is the Mother of all
things.

Always without desire we must be found,
If its deep mystery we would sound;
But if desire always within us be,
Its outer fringe is all that we shall see.

Under these two aspects, it is really the same; but as development
takes place, it receives the different names. Together we call them
the Mystery. Where the Mystery is the deepest is the gate of all that
is subtle and wonderful.

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2
All in the world know the beauty of the beautiful, and in doing
this they have (the idea of) what ugliness is; they all know the skill
of the skilful, and in doing this they have (the idea of) what the
want of skill is.

So it is that existence and non-existence give birth the one to
(the idea of) the other; that difficulty and ease produce the one (the
idea of) the other; that length and shortness fashion out the one the
figure of the other; that (the ideas of) height and lowness arise from
the contrast of the one with the other; that the musical notes and
tones become harmonious through the relation of one with another; and
that being before and behind give the idea of one following another.

Therefore the sage manages affairs without doing anything, and
conveys his instructions without the use of speech.