Under heaven all can see beauty as beauty only because there is ugliness. All can know good as good only because there is evil. Therefore having and not having arise together. Difficult and easy complement each other. Long and short contrast each other. High and low rest upon each other. Voice and sound harmonize each other. Front and back follow one another.
LaoziClay is moulded to make a vessel, but the utility of the vessel lies in the space where there is nothing. . . . Thus, taking advantage of what is, we recognize the utility of what is not.
Laozi