The Book of Changes is one of the classics of ancient Chinese philosophy. It contains many profound thoughts and philosophy. 1. Yin-Yang Thought: The Book of Changes believes that all things in the universe are composed of Yin and Yang, and the two are mutually transformed and dependent. This ideology influenced various fields of Chinese culture, such as Chinese medicine, martial arts, philosophy, etc. 2. Changing thoughts: The Book of Changes believes that everything is constantly changing and developing. This change can be positive or negative. It emphasized the importance of adapting to change and also proposed the idea of "governing by doing nothing." 3. The idea of divinatory symbols: The Book of Changes uses the divinatory symbols of the Eight Trigrams and the 64 divinatory symbols to describe different things and situations. These divinatory symbols can be transformed and combined to reveal the nature and changing laws of things. 4. Moral thoughts: The Book of Changes puts forward the concept of "virtue", which is a person's moral character and cultivation. It believed that only through moral self-discipline and continuous cultivation could one reach the peak of life. The divination method of the Book of Changes can predict future changes and trends, but it also emphasizes the concept of "uncertainty". This kind of thinking inspired people to calmly face the uncertainty of prediction and not rely too much on divination. These are some of the essence of the Book of Changes. They have influenced various fields of Chinese culture and philosophy, and have also had a profound impact on the development of philosophy and science in the world.