Listen to this articlexiānɡfǎn-xiānɡchénɡ 相反相成
Being both Opposite and Complementary
处于对立关系中的两个事物之间既相互排斥又相互成就、相互转化。一切事物都处于与他者的对立之中。对立双方具有相反的性质或意义，因而彼此间是相互排斥的，如有与无、长与短、高与下、善与恶、美与丑等。但同时，事物的性质或意义又是借由与之对立的事物而获得确立的，对立双方在一定条件下还可以相互转化。这一观念在先秦时期即已出现，在班固《汉书·艺文志》中始被概括为“相反相成”。
This term refers to two things that are mutually opposite to but complementing each other and that they mutually transform between them. Everything is an antithesis to something else. Both antithetic sides are opposite to each other. Therefore there is mutual exclusion between them, such as you and wu, long and short, high and low, good and bad, and beautiful and ugly. On the other hand, the nature or the identity of a thing is established due to something antithetic to it. The two opposing sides can transform into each other under certain conditions. This concept emerged in the pre-Qin period. In The History of the Han Dynasty written by Ban Gu, the idea was first defined as “two things being both opposite and complementary.”
引例 Citations：
◎天下皆知美之为美，斯恶已；皆知善之为善，斯不善已。故有无相生，难易相成，长短相形，高下相倾，音声相和，前后相随。（《老子·二章》）
（天下都知道美之所以为美，丑恶的观念也就产生了；都知道善之所以为善，不善的观念也就产生了。因此有和无相互生成，难和易相互成就，长和短相互形成，高和下相互包含，音和声相互调和，前和后相互随顺。）
People all know that ugliness exists as an antithesis of beauty and that evil exists as an antithesis of goodness. Likewise, you and wu produce each other; what is difficult and what is easy complement each other; long and short exist in contrast, so do high and low; tone and sound are in harmony with each other, and front and back exist because of each other. (Laozi)
◎仁之与义，敬之与和，相反而皆相成也。（《汉书·艺文志》）
（仁与义、敬与和，既相互排斥又相互成就。）
The relationship between benevolence and righteousness and between respect and harmony is one of mutual opposition and complementation. (The History of the Han Dynasty)
