A passage from the Dao De Jing that I read tonight in the opening ritual of the May Day gathering:

Each of us can know beauty
Only because there is ugliness.
Each of us can know truth
Only because there is falsehood.

Life and death give birth to each other.
Difficult and easy complete each other.
Long and short give shape to each other.
High and low depend on each other.
Sound and silence sing with each other.
Past and future follow each other.