What are the four principles in Zhang Qicheng's Book of Changes?

Harmony between man and nature, balance between yin and yang, causal cycle, flexibility and impermanence.

1. Harmony between man and nature: The Book of Changes holds that human life and everything in nature are interrelated, isomorphic and interdependent.

2. Balance of Yin and Yang: The Eight Diagrams in the Book of Changes represent various natural phenomena and characteristics in the universe, including the balance of Yin and Yang and their poles.

3. Causal cycle: I ching believes that people's words and deeds will have a causal relationship, which will in turn affect themselves at some point in the future.

4. Flexibility and impermanence: The sixty-four hexagrams in the Book of Changes represent various life realms and universal laws, which are interrelated and transformed with each other.