During the T'ang Dynasty，due to prevailing circumstances, there was an interflux between Confucianism，Buddhism and Taoism，but on the doctrinal aspect，Buddhism was strong and Confucianism was weak. Hence，Han-yu advocated the revival of Confucian studies in order to strengthen the traditional status of Confucianism. His approach was to discriminate against Buddhism and Taoism to uphold Confucianism. This antagonism had to do with him under the influence of Confucianists since an early age，and was unfamiliar with Buddhism. Lui Tzung-yuan advocated a union between Confucianism and Buddhism by stating their differences and discerning their similarities. He had an in-depth knowledge of Buddhist studies and Pai-chia (百家). After having lived through rough times, he even used Buddhist studies as his spiritual solace，and made friends with student monks who did not favour official position nor fought for competence. He disapproved of Han-yu's discrimination of Buddhism, and sought ways for mutual assimilation between Confuciansm and Buddhism. For the new direction which Confucian studies through assimilation of Buddhist studies had developed，he had supplied the inspiration，and this represented the main stream for Confucian studies and the advancement of Chinese culture. But he had not formulated a specific treatise to explain it. Li-ao in avoiding the respective mistakes of Han-yu and Lui Tzung-yuan,wrote Fu-hsing-shu (復性書) in which he wrote favourably on Buddhism and Confucianism，and formulated the theory of the eradication of sentiment and recovering one's true nature. This theory has a parallel in Buddhist ideas of "seeing nature and becoming Buddha" and "no thought as the sect". During the transition period of Confucian studies of the T'ang Dynasty to Neo-Confucianism of the Sung Dynasty，Han- yu pointed out the necessity of reviving Confucian studies; he had proposed a mission. Lui Tzung-yuan pointed out the inevitability of Confucian studies accommodating Buddhist studies; he had found the right avenue. Li-ao actually carried out an attempted theoretical inquiry into Confucian studies. From different angles, the three of them respectively had laid the ground work for the rise of Neo- Confucianism of the Sung Dynasty.
