Answer: Zhouyi, Laozi, Zhuangzi.

Analysis: Metaphysics scholars in Wei and Jin Dynasties are collectively called Laozi, Zhuangzi and Zhouyi. Taoism is also used. Yan Zhitui in the Northern Qi Dynasty wrote "Mianxue of Yan Family Instructions": "I was born in the Liang Dynasty, so I reinterpret it. Zhuang, Lao and Zhouyi are always called San Xuan. " "Biography of Sui Shu Hermit Xu Zechuan": "You are good at San Xuan and good at discussion."

During the Wei, Jin, Southern and Northern Dynasties, in order to oppose the rigid study of images and numbers at that time, thinkers created many famous religions with false filial piety and morality, and drew nutrition from Zhuangzi, Zhouyi and Laozi, and founded the Metaphysics School.

"Difficult, changeable and simple"-Yi

Great changes have taken place in the study of image number in Han Dynasty in Wei and Jin Dynasties. Like mathematics, it is judged by a relatively fixed model. For example, divination represents vitality. Take an animal as an analogy, that is, a horse, because horses are very athletic. It was settled in this way. Later, the representative of divination was the horse, and nothing else could be done. Therefore, Kun hexagrams represent suppleness. Take an animal as an analogy, that is, the cow, because the cow is very supple, and then it is fixed. Kun hexagrams represent cattle, and nothing else works. In the Wei and Jin Dynasties, people thought that this kind of mathematics was too rigid, and learning Zhouyi should mainly master its principles, not these rigid numbers.