Derived from 《
吕氏春秋·
博志》 (3rd century BC):
全则必缺,
极则必反 ('what is whole must become incomplete; what reaches its extreme must reverse'). Echoed in 《
鹖冠子·
环流》:
物极则反,
命曰环流 ('things at their extreme reverse, call this the circular flow'). It captures the Daoist intuition behind
阴阳: every yang peak conceals an emerging yin.