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（32-92）, the idea was first defined as “two things being both opposite and complementary.”

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)

The relationship between benevolence and righteousness and between respect and harmony is one of mutual opposition and complementation. (The History of the Han Dynasty)