Zhou Dunyi was a Chinese cosmologist, philosopher, and writer during the Song dynasty. He conceptualized the Neo-Confucian cosmology of the day, explaining the relationship between human conduct and universal forces. In this way, he emphasizes that humans can master their qi ("spirit") in order to accord with nature. He was a major influence to Zhu Xi, who was the architect of Neo-Confucianism. Zhou Dunyi was mainly concerned with Taiji and Wuji, the yin and yang, and the wu xing.