Interdependence

"When the people of the Earth all know beauty as beauty,
There arises (the recognition of) ugliness.
When the people of the Earth all know the good as good,
There arises (the recognition of) evil.

Therefore:
Being and non-being interdepend in growth;
Difficult and easy interdepend in completion;
Long and short interdepend in contrast;
High and low interdepend in position;
Tones and voice interdepend in harmony;
Front and behind interdepend in company."

Book of Tao