So it is that existence and non-existence give birth the
Books:
THE TAO AND ITS CHARACTERISTICS
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