Zhou Dunyi was the first eleventh-century Chinese thinker who argued for the inseparability of metaphysics and ethics. His two works—Taiji tushuo (An Explanation of the Diagram of the Great Ultimate) and Tongshu (Penetrating the Book of Changes)—were major neo-Confucian writings on the metaphysical nature of moral cultivation.

In the Taiji tushuo, Zhou Dunyi comments on the Diagram of the Great Ultimate (Taiji tu). The Diagram, created by the Daoist Chen Tuan (c. 906–989), consists of five circles. The top circle is an empty one, symbolizing the universe as a self-generative and self-reproducing entity. The second circle contains intermixing semi-circles of dark and light colors, with the dark color representing the yin (the yielding cosmic force) and the light color the yang (the active cosmic force). The third circle is a group of five small circles, each represents one of the Five Phases (wu...