Dai-Zhen, Ching Dynasty, was born between Yong-Zheng and Qian-Long two emperors. Because of the fall of Ming Dynasty, the academic trend at the time shifted from pure theoretic practices to practical applications. This change provided the study of Chi an environment to mature. Thus, under this kind of atmosphere, Dai- Zhen switched from a firm supporter of Cheng-Chu Neo -Confucianism to opposing them; going as far as stating their principals contain elements of Buddhism and Daoism, therefore cannot represent the ideas of Confucius. This prompted him to try to find the true meaning of Confucius' ideas by studying old documents. Dai- Zhen complemented Lo-Chin Shun and Wang-Ting's idea of Chi, using "Yin-Yang and five elements, concrete content of the change of Chi" to illustrate how the different ratios of elements in a body can create various changes. Not only does this theory rationally explained the versatility of the world, it also pointed out how unpractical Cheng-Chu's "metaphysics" theory is at performing such task. Dai-Zhen also placed a great emphasis on the practical application of Chi, thinking that Chi can go through visible and invisible, not only diminishing the differences between man and nature, but also possessing a virtuous meaning. This implied that man has the ability to exercise virtuous deeds, making this versatile world not only humanistic, but also proving the value of man. So through Dai-Zhen's analyzing of Chi, we can conclude that in his understanding, nothing of this world is born without the aid of the Ying and the Yang.