First, it belongs to the orthodox Confucian doctrine after Qin and Han Dynasties. According to the concept of chiseling, it is considered that the connotation of "Yi" includes three meanings:
(1) Easy. It means easy. Because the natural laws of heaven and earth are so simple.
(2) change. It is believed that all things in nature, as well as people, are constantly changing interactively and endlessly. However, the law of this change has its inevitable criteria to follow, not random changes.
(3) It is not easy. Everything in the world, as well as personnel, is changing in a complicated and mutually causal way at any time and anywhere, but what is changing is its phenomenon. It is not easy to change, but it is simple.